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Mechanical Engineers Data Handbook

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Abstract

There are several good mechanical engineering data books on the market but these tend to be very bulky and expensive, and are usually only available in libraries as reference books.

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Engineering design involves the correct determination of the sizes of components to withstand the maximum stress due to combinations of direct, bending and shear loads. The following deals with the different types of stress and their combinations. Only the case of two- dimensional stress is dealt with, although many cases of three-dimensional stress combinations occur. The theory is applied to the special case of shafts under both torsion and bending. l.f Types of stress
Engineering design involves the correct determination of the sizes of components to withstand the maximum stress due to combinations of direct, bending and shear loads. The following deals with the different types of stress and their combinations. Only the case of two- dimensional stress is dealt with, although many cases of three-dimensional stress combinations occur. The theory is applied to the special case of shafts under both torsion and bending. l.f Types of stress
MECHANICAL ENGINEER’S DATA HANDBOOK Relationship between elastic constants
MECHANICAL ENGINEER’S DATA HANDBOOK Relationship between elastic constants
M and torque 7, the maximum direct and shear stresses, o,, and 7,, are equal to those produced by ‘equivalent’ moments M, and T. where A compound bar is one composed of two or more bars of different materials rigidly joined. The stress when loaded depends on the cross-sectional areas (A, and A,) areas and Young’s moduli (E, and E,) of the components. In many components the load may be suddenly applied to give stresses much higher than the steady stress. An example of stress due to a falling mass is given. Maximum tensile stress in bar
M and torque 7, the maximum direct and shear stresses, o,, and 7,, are equal to those produced by ‘equivalent’ moments M, and T. where A compound bar is one composed of two or more bars of different materials rigidly joined. The stress when loaded depends on the cross-sectional areas (A, and A,) areas and Young’s moduli (E, and E,) of the components. In many components the load may be suddenly applied to give stresses much higher than the steady stress. An example of stress due to a falling mass is given. Maximum tensile stress in bar
For a hollow shaft to have the same strength as an equivalent solid shaft:
For a hollow shaft to have the same strength as an equivalent solid shaft:
Thin rectangular bar and thin open section
Thin rectangular bar and thin open section
Approximate dimensions of bolt heads and nuts (ISO metric precision)
Approximate dimensions of bolt heads and nuts (ISO metric precision)
Bracket under bending moment Shear stress t=4P/nD? Shear stress t= 2P/nD?
Bracket under bending moment Shear stress t=4P/nD? Shear stress t= 2P/nD?
This deals with bolts in single and double shear. The crushing stress is also important. Maximum tensile stress ¢,,=¢,+ P/(nA) for bolt at a,
This deals with bolts in single and double shear. The crushing stress is also important. Maximum tensile stress ¢,,=¢,+ P/(nA) for bolt at a,
1.2.5 Strength of welds A well-made ‘butt weld’ has a strength at least equal to that of the plates joined. In the case of a ‘fillet weld’ in shear the weld cross section is assumed to be a 45° right-angle triangle with the shear area at 45° to the plates. For transverse loading an angle of 67.5° is assumed as shown.
1.2.5 Strength of welds A well-made ‘butt weld’ has a strength at least equal to that of the plates joined. In the case of a ‘fillet weld’ in shear the weld cross section is assumed to be a 45° right-angle triangle with the shear area at 45° to the plates. For transverse loading an angle of 67.5° is assumed as shown.
The load which can be taken is proportional to the number of rows.
The load which can be taken is proportional to the number of rows.
Z=1/Yma, = bending modulus
Z=1/Yma, = bending modulus
LZTIVNE SVG! OLteoD a: re ed where: A=total area of weld at throat, F =load.
LZTIVNE SVG! OLteoD a: re ed where: A=total area of weld at throat, F =load.
Resultant stress {t,) is the vector sum of t, and 1,; r is chosen to give highest value of t,. From t, the value of t is found, and hence w.
Resultant stress {t,) is the vector sum of t, and 1,; r is chosen to give highest value of t,. From t, the value of t is found, and hence w.
The stress varies from zero to a maximum tensile or compressive stress, of magnitude 2¢,. The average value is o,, with a superimposed alternat- ing stress of range o,.
The stress varies from zero to a maximum tensile or compressive stress, of magnitude 2¢,. The average value is o,, with a superimposed alternat- ing stress of range o,.
The number of cycles N of alternating stress to cause failure and the magnitude of the stress o, are plotted. At N=0, failure occurs at o,, the ultimate tensile strength. At a lower stress o,, known as the ‘endurance limit’, failure occurs, in the case of steel, as N approaches infinity. In the case of non-ferrous metals, alloys and plastics, the curve does not flatten out anda ‘fatigue stress’ of. for a finite number of stress reversals N! is specified.
The number of cycles N of alternating stress to cause failure and the magnitude of the stress o, are plotted. At N=0, failure occurs at o,, the ultimate tensile strength. At a lower stress o,, known as the ‘endurance limit’, failure occurs, in the case of steel, as N approaches infinity. In the case of non-ferrous metals, alloys and plastics, the curve does not flatten out anda ‘fatigue stress’ of. for a finite number of stress reversals N! is specified.
ii _ At a discontinuity such as a notch, hole or step, the stress is much higher than the average value by a factor K, which is known as the ‘stress concentration factor’. The Soderberg diagram shows the alternating and steady stress components, the former being multiplied by K, in relation to a safe working line and a factor of safety.
ii _ At a discontinuity such as a notch, hole or step, the stress is much higher than the average value by a factor K, which is known as the ‘stress concentration factor’. The Soderberg diagram shows the alternating and steady stress components, the former being multiplied by K, in relation to a safe working line and a factor of safety.
There is no endurance limit and the fatigue stress is taken at a definite value of stress reversals, e.g. 5 x 10”. Some typical values are given.
There is no endurance limit and the fatigue stress is taken at a definite value of stress reversals, e.g. 5 x 10”. Some typical values are given.
Wrought aluminium alloys Effect of surface finish on endurance limit Plastics
Wrought aluminium alloys Effect of surface finish on endurance limit Plastics
There are also factors which depend upon size, tem- perature, etc. The values of endurance limits and fatigue stress given are based on tests on highly polished small specimens. For other types of surface the endurance limit must be multiplied by a suitable factor which varies with tensile strength. Values are given for a tensile strength of 1400 N mm ~?.
There are also factors which depend upon size, tem- perature, etc. The values of endurance limits and fatigue stress given are based on tests on highly polished small specimens. For other types of surface the endurance limit must be multiplied by a suitable factor which varies with tensile strength. Values are given for a tensile strength of 1400 N mm ~?.
Highest value of stress at a discontinuity
Highest value of stress at a discontinuity
Typical stress concentration factors for various features
Typical stress concentration factors for various features
Example Fora cantilever with an end load W and a distributed load w, per unit length. Due to W only: S,=W; M,=WL; y, = WL3/3EI Due to w only: S,=wL; M,=wL?/2; y,=wL*/8EI For both W and w: S.=W+wLl; M,=WL+wL?/2; y, = WLI /3EL+wLl*/8El
Example Fora cantilever with an end load W and a distributed load w, per unit length. Due to W only: S,=W; M,=WL; y, = WL3/3EI Due to w only: S,=wL; M,=wL?/2; y,=wL*/8EI For both W and w: S.=W+wLl; M,=WL+wL?/2; y, = WLI /3EL+wLl*/8El
1.4.4 Bending of thick curved bars
1.4.4 Bending of thick curved bars
Stresses in a loaded thick ring
Stresses in a loaded thick ring
Maximum bending moment (at A and B):
Maximum bending moment (at A and B):
Uniform cantilever, beam mass only
Uniform cantilever, beam mass only
Springs are used extensively in engineering to control movement, apply forces, limit impact forces, reduce vibration and for force measurement. 1.5.1 Helical torsion and spiral springs This consists of a wire of circular or rectangular cross-section, wrapped around an imaginary cylinder to form a helix. Springs may be ‘compression’, with flat ends, or ‘tension’ with loading hooks. Helical springs may also be used as ‘torsion’ springs. Formulae are given for stress and deflection as well as frequency of vibration.
Springs are used extensively in engineering to control movement, apply forces, limit impact forces, reduce vibration and for force measurement. 1.5.1 Helical torsion and spiral springs This consists of a wire of circular or rectangular cross-section, wrapped around an imaginary cylinder to form a helix. Springs may be ‘compression’, with flat ends, or ‘tension’ with loading hooks. Helical springs may also be used as ‘torsion’ springs. Formulae are given for stress and deflection as well as frequency of vibration.
Angle of twist (for torque 7) @=647Dn/Ed* Maximum bending stress o,, =327/nd?
Angle of twist (for torque 7) @=647Dn/Ed* Maximum bending stress o,, =327/nd?
The formulae for load and stiffness are the same. There is usually no initial clearance between coils, and there is an initial ‘built-in’ compression. Various types of end hooks are used.
The formulae for load and stiffness are the same. There is usually no initial clearance between coils, and there is an initial ‘built-in’ compression. Various types of end hooks are used.
Allowable working stress (MPa) for helical springs (grade 060496)
Allowable working stress (MPa) for helical springs (grade 060496)
A spiral spring consists ofa strip or wire wound ina flat spiral subjected to a torque to give an angular deflection. The clock spring is an example. Equation of spiral D=D,+ pa/n
A spiral spring consists ofa strip or wire wound ina flat spiral subjected to a torque to give an angular deflection. The clock spring is an example. Equation of spiral D=D,+ pa/n
Conical helical spring This is a helical spring in which the coils progressively change in diameter to give increasing stiffness with increasing load. It has the advantage that the com- pressed height is small. This type of spring is used for upholstery.
Conical helical spring This is a helical spring in which the coils progressively change in diameter to give increasing stiffness with increasing load. It has the advantage that the com- pressed height is small. This type of spring is used for upholstery.
(positive for A, negative for B. Stress is positive or negative depending on the value of y)
(positive for A, negative for B. Stress is positive or negative depending on the value of y)
Springs of rubber bonded to metal are made in a wide variety of configurations. The rubber is usually in shear and, because of the high internal damping, such springs are used for limiting vibrations.
Springs of rubber bonded to metal are made in a wide variety of configurations. The rubber is usually in shear and, because of the high internal damping, such springs are used for limiting vibrations.
Strain energy u=C,o2,,/2E or C,t*,,/2G per unit volume
Strain energy u=C,o2,,/2E or C,t*,,/2G per unit volume
diagrams for each plane, moments M, and M, may be found and also reactions ,R,, \R,, ,R, and ,R,- av
diagrams for each plane, moments M, and M, may be found and also reactions ,R,, \R,, ,R, and ,R,- av
horizontal components, as before. The forces are shown for a shaft AB with two gears.
horizontal components, as before. The forces are shown for a shaft AB with two gears.
The main types of key are the ‘rectangular’ where the keyways are half the key depth, the ‘feather’ where the keyway is closed at each end, the ‘Gib-head’ used always at the end of a shaft and with a head so that it can be tapped into place, the ‘Woodruff key’ which is segmental and for use on tapered shafts, and the inexpensive ‘saddle’ and ‘round’ keys.
The main types of key are the ‘rectangular’ where the keyways are half the key depth, the ‘feather’ where the keyway is closed at each end, the ‘Gib-head’ used always at the end of a shaft and with a head so that it can be tapped into place, the ‘Woodruff key’ which is segmental and for use on tapered shafts, and the inexpensive ‘saddle’ and ‘round’ keys.
A large variety of flexible couplings are used to accommodate angular, parallel or axial misalignment. Several types are shown.
A large variety of flexible couplings are used to accommodate angular, parallel or axial misalignment. Several types are shown.
Shaft couplings may be ‘solid’ or ‘flexible’. Soli couplings may consist simply of a sleeve joining th shafts, the drive being taken by pins or keys. For larg powers, bolted flanges are used to give either a solid o flexible coupling.
Shaft couplings may be ‘solid’ or ‘flexible’. Soli couplings may consist simply of a sleeve joining th shafts, the drive being taken by pins or keys. For larg powers, bolted flanges are used to give either a solid o flexible coupling.
Bonded rubber couplings are simple and cheap and permit large misalignments. Their non-linear charac- teristics make them useful for detuning purposes. Three annular types are shown and their spring constants given.
Bonded rubber couplings are simple and cheap and permit large misalignments. Their non-linear charac- teristics make them useful for detuning purposes. Three annular types are shown and their spring constants given.
MECHANICAL ENGINEER’S DATA HANDBOOK A component subject to compression is known as a ‘strut’ if it is relatively long and prone to ‘buckling’. A short column fails due to shearing when the compres- sive stress is too high, a strut fails when a critical load called the ‘buckling’ or ‘crippling’ load causes sudden bending. The resistance to buckling is determined by the ‘flexural rigidity’ EI or EAk, where k is the leas:
MECHANICAL ENGINEER’S DATA HANDBOOK A component subject to compression is known as a ‘strut’ if it is relatively long and prone to ‘buckling’. A short column fails due to shearing when the compres- sive stress is too high, a strut fails when a critical load called the ‘buckling’ or ‘crippling’ load causes sudden bending. The resistance to buckling is determined by the ‘flexural rigidity’ EI or EAk, where k is the leas:
MECHANICAL ENGINEER’S DATA HANDBOOK 1.8 Cylinders and hollow spheres failure may be due to buckling. In the following, p is the difference between the internal and external pres- sures, In engineering there are many examples of hollow cylindrical and spherical vessels subject to internal or external pressure. The formulae given are based on Lamé’s equations. In the case of external pressure,
MECHANICAL ENGINEER’S DATA HANDBOOK 1.8 Cylinders and hollow spheres failure may be due to buckling. In the following, p is the difference between the internal and external pres- sures, In engineering there are many examples of hollow cylindrical and spherical vessels subject to internal or external pressure. The formulae given are based on Lamé’s equations. In the case of external pressure,
P,=axial force to give interference fit a=coefficient of linear expansion of inner or outer cylinder At=temnerature difference hetween cylinders x= 2ar,At
P,=axial force to give interference fit a=coefficient of linear expansion of inner or outer cylinder At=temnerature difference hetween cylinders x= 2ar,At
1.8.2 Shrink fit of cylinders Two hollow cylindrical parts may be connected to: gether by shrinking or press-fitting where a contac pressure is produced. In the case ofa hub ona shaft thi: eliminates the need for a key. Formulae are given fo: the resulting stresses, axial fitting force and the result. ing torque capacity in the case of a shaft.
1.8.2 Shrink fit of cylinders Two hollow cylindrical parts may be connected to: gether by shrinking or press-fitting where a contac pressure is produced. In the case ofa hub ona shaft thi: eliminates the need for a key. Formulae are given fo: the resulting stresses, axial fitting force and the result. ing torque capacity in the case of a shaft.
rectangular contact area of very small width. The following gives the size of these areas and the maxi- mum stress for several common cases. The theory is of great importance in the design of rolling bearings. When a ball is in contact with a flat, concave or convex surface, a small contact area is formed, the size of the area depending on the load and materials. In the case of a roller, a line contact is obtained, giving a
rectangular contact area of very small width. The following gives the size of these areas and the maxi- mum stress for several common cases. The theory is of great importance in the design of rolling bearings. When a ball is in contact with a flat, concave or convex surface, a small contact area is formed, the size of the area depending on the load and materials. In the case of a roller, a line contact is obtained, giving a
Circular plate, uniform load, edges simply supported 1.10.1 Stress and deflection of circular flat plates
Circular plate, uniform load, edges simply supported 1.10.1 Stress and deflection of circular flat plates
Rectangular plate, concentrated load at centre, clamped edges (empirical) 0, =k ,P/t? (at middle of edge 6) Ym= k,Pa?/Et? (at centre) Rectangular plate, uniform load, clamped edges (empirice naz 1.10.2 Stress and deflection of rectangular flat plates
Rectangular plate, concentrated load at centre, clamped edges (empirical) 0, =k ,P/t? (at middle of edge 6) Ym= k,Pa?/Et? (at centre) Rectangular plate, uniform load, clamped edges (empirice naz 1.10.2 Stress and deflection of rectangular flat plates
nents of these forces in the x and y directions and constructing a triangle of forces. The force vectors may be added by drawing a polygon of forces. The line completing the polygon is the resultant (note that its arrow points in the opposite direction), and its angle to a reference direction may be found.
nents of these forces in the x and y directions and constructing a triangle of forces. The force vectors may be added by drawing a polygon of forces. The line completing the polygon is the resultant (note that its arrow points in the opposite direction), and its angle to a reference direction may be found.
A force may be resolved into two forces at right angles to one another. The force F shown is at angle @ to axis XX and has components: If several forces F,, F 2, F 3, etc., act on a body, then the resultant force may be found by adding the compo-
A force may be resolved into two forces at right angles to one another. The force F shown is at angle @ to axis XX and has components: If several forces F,, F 2, F 3, etc., act on a body, then the resultant force may be found by adding the compo-
Resolution of a moment into a force and a couple This is independant of d and the resultant force is zero. Such a moment is called a ‘couple’. For a force F at a from point O; if equal and opposite forces are applied at O, then the result is a couple Fa and a net force F. M=F,—F(d—a)=Fa If two equal and opposite forces have parallel lines of action a distance a apart, the moment about any point O at distance d from one of the lines of action is
Resolution of a moment into a force and a couple This is independant of d and the resultant force is zero. Such a moment is called a ‘couple’. For a force F at a from point O; if equal and opposite forces are applied at O, then the result is a couple Fa and a net force F. M=F,—F(d—a)=Fa If two equal and opposite forces have parallel lines of action a distance a apart, the moment about any point O at distance d from one of the lines of action is
A system of forces is balanced, i.e, in equilibrium, when the resultant F, is zero, in which case its components F, and F, are each zero.
A system of forces is balanced, i.e, in equilibrium, when the resultant F, is zero, in which case its components F, and F, are each zero.
Velocities after impact (velocities positive to right): Note: e=1! for perfectly elastic spheres; e=0 for inelastic spheres.
Velocities after impact (velocities positive to right): Note: e=1! for perfectly elastic spheres; e=0 for inelastic spheres.
2.1.11 Centre of percussion MECHANICAL ENGINEER’S DATA HANDBOOK
2.1.11 Centre of percussion MECHANICAL ENGINEER’S DATA HANDBOOK
The following table gives useful information on the sun, moon and earth. 2.1.16 The solar system
The following table gives useful information on the sun, moon and earth. 2.1.16 The solar system
When a projectile is fired at an angle to a horizontal plane under gravity, the trajectory is a parabola if air resistance is neglected. It can be shown that the
When a projectile is fired at an angle to a horizontal plane under gravity, the trajectory is a parabola if air resistance is neglected. It can be shown that the
For a rocket travelling vertically against gravity, the mass of fuel is continually decreasing as the fuel is burnt, i.e. the total mass being lifted decreases uni- formly with time.
For a rocket travelling vertically against gravity, the mass of fuel is continually decreasing as the fuel is burnt, i.e. the total mass being lifted decreases uni- formly with time.
The forces are: m,r,@?, m,r,w”, etc. These are re- solved into vertical and horizontal components:
The forces are: m,r,@?, m,r,w”, etc. These are re- solved into vertical and horizontal components:
Several out of balance masses in one plane
Several out of balance masses in one plane
2.3.2 Reciprocating masses Using the same symbols as in the previous section:
2.3.2 Reciprocating masses Using the same symbols as in the previous section:
If K is under about 0.3, it is accurate enough to use only the first two terms containing 6 in each formula. Flywheels are used for the storing of energy in a rotating machine and to limit speed fluctuations. Formulae are given for the calculation of the moment of inertia of flywheels and for speed and energy fluctuation.
If K is under about 0.3, it is accurate enough to use only the first two terms containing 6 in each formula. Flywheels are used for the storing of energy in a rotating machine and to limit speed fluctuations. Formulae are given for the calculation of the moment of inertia of flywheels and for speed and energy fluctuation.
This is a type of flexible shaft coupling used extensively for vehicle drives. They are used in pairs when there is parallel misalignment.
This is a type of flexible shaft coupling used extensively for vehicle drives. They are used in pairs when there is parallel misalignment.
A cam is a mechanism which involves sliding contact and which converts one type of motion into another, e.g. rotary to reciprocating. Most cams are of the radial type, but axial rotary cams are also used. Cams may have linear motion. The motion is transmitted through a ‘follower’ and four types are shown for radial cams.
A cam is a mechanism which involves sliding contact and which converts one type of motion into another, e.g. rotary to reciprocating. Most cams are of the radial type, but axial rotary cams are also used. Cams may have linear motion. The motion is transmitted through a ‘follower’ and four types are shown for radial cams.
Acceleration a=0 during rise and fall but infinite at direction reversal.
Acceleration a=0 during rise and fall but infinite at direction reversal.
The following refers to the motion of the roller centre.
The following refers to the motion of the roller centre.
A governor is a device which controls the speed of sngine, a motor or other machine by regulating the fi or power supply. The controlled speed is called t isochronous speed’. Electronic systems are also ava able.
A governor is a device which controls the speed of sngine, a motor or other machine by regulating the fi or power supply. The controlled speed is called t isochronous speed’. Electronic systems are also ava able.
The vee thread is used extensively for nuts, bolts and screws. The thread may be produced by machining but rolling is much cheaper. Used for power transmission. The friction is low and there is no radial force on the nut. Vee thread
The vee thread is used extensively for nuts, bolts and screws. The thread may be produced by machining but rolling is much cheaper. Used for power transmission. The friction is low and there is no radial force on the nut. Vee thread
Used for power transmission. Has greater root strength and is easier to machine than the square thread. Used for lathe lead screw. Acme thread
Used for power transmission. Has greater root strength and is easier to machine than the square thread. Used for lathe lead screw. Acme thread
The resistance of a vehicle to motion is made up of ‘rolling resistance’, ‘gradient force’ and ‘aerodynamic drag’. From the total resistance and a knowledge of the overall efficiency of the drive, the power can be calculated. Additional power is required to accelerate the vehicle. Braking torque is also dealt with. 2.5 Automobile mechanics
The resistance of a vehicle to motion is made up of ‘rolling resistance’, ‘gradient force’ and ‘aerodynamic drag’. From the total resistance and a knowledge of the overall efficiency of the drive, the power can be calculated. Additional power is required to accelerate the vehicle. Braking torque is also dealt with. 2.5 Automobile mechanics
Coefficient of adbesion for different surfaces N,=engine speed N,,= wheel speed r= wheel effective radius F,,=wheel force (4 wheels.
Coefficient of adbesion for different surfaces N,=engine speed N,,= wheel speed r= wheel effective radius F,,=wheel force (4 wheels.
Let the applied force be F,=F coswt. When steady conditions are attained the mass will vibrate at the frequency of the applied force. The amplitude varies with frequency as follows:
Let the applied force be F,=F coswt. When steady conditions are attained the mass will vibrate at the frequency of the applied force. The amplitude varies with frequency as follows:
AR is a measure of the rate at which the amplitude falls with successive oscillations.
AR is a measure of the rate at which the amplitude falls with successive oscillations.
F=m,aw? cos ct (due to mass m, rotating at radius a angular velocity w)
F=m,aw? cos ct (due to mass m, rotating at radius a angular velocity w)
MECHANICAL ENGINEER’S DATA HANDBOOK
MECHANICAL ENGINEER’S DATA HANDBOOK
Force horizontal The force to move a wheeled vehicle F,=y,N where: y, =rolling coefficient of resistance, N = wheel reaction.
Force horizontal The force to move a wheeled vehicle F,=y,N where: y, =rolling coefficient of resistance, N = wheel reaction.
Force Q normal to force (F), F=2Q tan(«+¢) where: p=tan @. Square section thread
Force Q normal to force (F), F=2Q tan(«+¢) where: p=tan @. Square section thread
The following tables give coefficients of friction for general combinations of materials, clutch and brake materials, machine tool slides and for rubber on asphalt and concrete.
The following tables give coefficients of friction for general combinations of materials, clutch and brake materials, machine tool slides and for rubber on asphalt and concrete.
MECHANICAL ENGINEER’S DATA HANDBOOK Machine tool slides
MECHANICAL ENGINEER’S DATA HANDBOOK Machine tool slides
Use the positive sign for directions shown in the figure and the negative sign for opposite rotation (greater torque). The friction force is applied through a block made of, or lined with, a friction material. The brake can operate with either direction of rotation, but the friction torque is greater in one direction than the other. As in all friction brakes the limiting factor is the allowable pressure on the friction material.
Use the positive sign for directions shown in the figure and the negative sign for opposite rotation (greater torque). The friction force is applied through a block made of, or lined with, a friction material. The brake can operate with either direction of rotation, but the friction torque is greater in one direction than the other. As in all friction brakes the limiting factor is the allowable pressure on the friction material.
In this case the dimensions can be chosen so that the brake is ‘self-locking’, i-e. no force is required, or it can operate in the opposite direction.
In this case the dimensions can be chosen so that the brake is ‘self-locking’, i-e. no force is required, or it can operate in the opposite direction.
The brake is released by a force greater than F. Here the friction force is applied around a large angle. The torque is increased by a factor K which is a function of the angle of contact. The shoe subtends an angle of 26 and is pivoted at ‘h’ where
The brake is released by a force greater than F. Here the friction force is applied around a large angle. The torque is increased by a factor K which is a function of the angle of contact. The shoe subtends an angle of 26 and is pivoted at ‘h’ where
The theory is the same as for the disk clutch but with an effective coefficient of friction A number of double-sided friction plates may be mounted on splines on one element, and correspond- ing stee] contacting plates on splines on the other element. The assembly is compressed by a spring or springs to give a torque capacity proportional to the number of pairs of contacting surfaces. }=cone angle (to the shaft axis, from 8° upwards). By angling the contacting surfaces, the torque capacity is increased; for example, for an angle of 9.6° the capacity is increased by a factor of 6.
The theory is the same as for the disk clutch but with an effective coefficient of friction A number of double-sided friction plates may be mounted on splines on one element, and correspond- ing stee] contacting plates on splines on the other element. The assembly is compressed by a spring or springs to give a torque capacity proportional to the number of pairs of contacting surfaces. }=cone angle (to the shaft axis, from 8° upwards). By angling the contacting surfaces, the torque capacity is increased; for example, for an angle of 9.6° the capacity is increased by a factor of 6.
The simplest type of clutch is the single-plate clutch in which an annular plate with a surface of friction material is forced against a metal disk by means of a spring, or springs, or by other means. There are two theories which give slightly different values of torque capacity.
The simplest type of clutch is the single-plate clutch in which an annular plate with a surface of friction material is forced against a metal disk by means of a spring, or springs, or by other means. There are two theories which give slightly different values of torque capacity.
Important factors are, load capacity, length to diameter ratio, and allowable pressure on bearing material. Wf... 4% Information is also given on rolling bearings. 9.1 Lightly loaded plain bearings awl. P= power L=length D=diameter u=absolute viscosity t=radial clearance r, =inner radius r,=outer radius N=rotational speed
Important factors are, load capacity, length to diameter ratio, and allowable pressure on bearing material. Wf... 4% Information is also given on rolling bearings. 9.1 Lightly loaded plain bearings awl. P= power L=length D=diameter u=absolute viscosity t=radial clearance r, =inner radius r,=outer radius N=rotational speed
Porous metals and non-metals 2.9.4 Surface finish and clearance for bearings
Porous metals and non-metals 2.9.4 Surface finish and clearance for bearings
MECHANICAL ENGINEER’S DATA HANDBOOK
MECHANICAL ENGINEER’S DATA HANDBOOK
N=revolutions per minute, D=diameter (mm).
N=revolutions per minute, D=diameter (mm).
The bearing load should be multiplied by the following factor when selecting a bearing. 1.9.8 Coefficient of friction for bearings Plain bearings — boundary lubrication 2.9.7 Service factor for rolling bearings
The bearing load should be multiplied by the following factor when selecting a bearing. 1.9.8 Coefficient of friction for bearings Plain bearings — boundary lubrication 2.9.7 Service factor for rolling bearings
MECHANICAL ENGINEER’S DATA HANDBOOK Height of tooth =2.25m
MECHANICAL ENGINEER’S DATA HANDBOOK Height of tooth =2.25m
In this case there is an additional component of force F, in the axial direction. 2.10.4 Helical spur gears
In this case there is an additional component of force F, in the axial direction. 2.10.4 Helical spur gears
For the diagram shown the signs are ‘+’ for F, and ‘—° for F,. The signs are reversed if the hand of the helix is reversed or the speed is reversed; they remain the same if both are reversed.
For the diagram shown the signs are ‘+’ for F, and ‘—° for F,. The signs are reversed if the hand of the helix is reversed or the speed is reversed; they remain the same if both are reversed.
To eliminate the axial thrust, gears have two sections with helices of opposite hand. These are also called ‘herringbone gears’.
To eliminate the axial thrust, gears have two sections with helices of opposite hand. These are also called ‘herringbone gears’.
2.10.7 Epicyclic gears MECHANICAL ENGINEER’S DATA HANDBOOK
2.10.7 Epicyclic gears MECHANICAL ENGINEER’S DATA HANDBOOK
Ratio of output to input speed for various types
Ratio of output to input speed for various types
Ina heat engine process from state | with surroundings at state 2 exergy is that part of the total enthalpy drop available for work production.
Ina heat engine process from state | with surroundings at state 2 exergy is that part of the total enthalpy drop available for work production.
Throttling (constant enthalpy process)
Throttling (constant enthalpy process)
The enthalpy is represented by the area under a constant pressure line on the T-s diagram. Area h, is the enthalpy of the liquid at saturation temperature, h,, is the enthalpy corresponding to the latent heat, Various processes are shown for a vapour on the 7-s diagram. AB is an isothermal] process in which a wet vapour becomes superheated. CD shows an isentropic expansion from the superheat to the wet region. EF isa polytropic process in the superheat region.
The enthalpy is represented by the area under a constant pressure line on the T-s diagram. Area h, is the enthalpy of the liquid at saturation temperature, h,, is the enthalpy corresponding to the latent heat, Various processes are shown for a vapour on the 7-s diagram. AB is an isothermal] process in which a wet vapour becomes superheated. CD shows an isentropic expansion from the superheat to the wet region. EF isa polytropic process in the superheat region.
and h,, is the superheat. The total enthalpy is, therefore, The dryness fraction at entropy s is
and h,, is the superheat. The total enthalpy is, therefore, The dryness fraction at entropy s is
3.4.1 Temperature conversion Lines of constant pressure, temperature, dryness frac- tion and specific volume are shown on the diagram. AB represents an isentropic process, AC a polytropic process and DE a constant enthalpy process. 3.3.5 Enthalpy-entropy (h-s) diagram
3.4.1 Temperature conversion Lines of constant pressure, temperature, dryness frac- tion and specific volume are shown on the diagram. AB represents an isentropic process, AC a polytropic process and DE a constant enthalpy process. 3.3.5 Enthalpy-entropy (h-s) diagram
Latent heat of fusion (kJ kg” ') at atmospheric pressure
Latent heat of fusion (kJ kg” ') at atmospheric pressure
3.4.2 Latent heats and boiling points
3.4.2 Latent heats and boiling points
Latent heat of evaporation (kJ kg~ ') at atmospheric pressure
Latent heat of evaporation (kJ kg~ ') at atmospheric pressure
Approximate analysis of air (suitable for calculations) General properties of air (at 300K, 1 bar)
Approximate analysis of air (suitable for calculations) General properties of air (at 300K, 1 bar)
Boiling point (°C) at atmospheric pressure 3.4.3 Properties of air
Boiling point (°C) at atmospheric pressure 3.4.3 Properties of air
Analysis of air
Analysis of air
Specific heat capacity of gases, gas constant and molecular weight (at normal pressure and temperature)
Specific heat capacity of gases, gas constant and molecular weight (at normal pressure and temperature)
3.6.2 Rankine cycle — with superheat In the ‘regenerative cycle’ efficiency is improved by bleeding off a proportion of the steam at an intermedi- ate pressure and mixing it with feed water pumped to the same pressure in a ‘feed heater’. Several feed heaters may be used but these are of the ‘closed’ variety to avoid the necessity for expensive pumps. The method is the same as for dry saturated steam. The graph shows the effect of superheat temperature on efficiency and specific steam consumption. In this case h, is the enthalpy for superheated steam.
3.6.2 Rankine cycle — with superheat In the ‘regenerative cycle’ efficiency is improved by bleeding off a proportion of the steam at an intermedi- ate pressure and mixing it with feed water pumped to the same pressure in a ‘feed heater’. Several feed heaters may be used but these are of the ‘closed’ variety to avoid the necessity for expensive pumps. The method is the same as for dry saturated steam. The graph shows the effect of superheat temperature on efficiency and specific steam consumption. In this case h, is the enthalpy for superheated steam.
3.6.3 Rankine cycle with reheat
3.6.3 Rankine cycle with reheat
in which case the steam leaves the last row axially. Two-row wheel Assume fB,=f,, k=1 and that all blades are symmetrical. 3.7.2. Impulse-reaction turbine
in which case the steam leaves the last row axially. Two-row wheel Assume fB,=f,, k=1 and that all blades are symmetrical. 3.7.2. Impulse-reaction turbine
3.8 Gas turbines
3.8 Gas turbines
MECHANICAL ENGINEER’S DATA HANDBOOK
MECHANICAL ENGINEER’S DATA HANDBOOK
This is the basic cycle for the petrol engine, the gas engine and the high-speed oil engine. Heat is supplied and rejected at constant volume, and expansion and compression take place isentropically. The thermal efficiency depends only on the compression ratio. 3.9.4 Diesel cycle (constant-pressure combustion)
This is the basic cycle for the petrol engine, the gas engine and the high-speed oil engine. Heat is supplied and rejected at constant volume, and expansion and compression take place isentropically. The thermal efficiency depends only on the compression ratio. 3.9.4 Diesel cycle (constant-pressure combustion)
In an engine with crankcase compression, the piston draws a new charge into the crankcase through a spring-loaded valve during the compression stroke. Ignition occurs just before TDC after which the working stroke commences. Near the end of the stroke the exhaust port is uncovered and the next charge enters the cylinder. The exhaust port closes shortly after the transfer port, and compression begins. The piston is shaped to minimize mixing of the new charge with the exhaust. (See section 3.10.3)
In an engine with crankcase compression, the piston draws a new charge into the crankcase through a spring-loaded valve during the compression stroke. Ignition occurs just before TDC after which the working stroke commences. Near the end of the stroke the exhaust port is uncovered and the next charge enters the cylinder. The exhaust port closes shortly after the transfer port, and compression begins. The piston is shaped to minimize mixing of the new charge with the exhaust. (See section 3.10.3)
where: N=number of revolutions per second, n=number of cylinders, A,=piston area (m2), L=stroke (m) Torque T=FR (Nm) where: F =force on brake arm (N), R=brake radius (m).
where: N=number of revolutions per second, n=number of cylinders, A,=piston area (m2), L=stroke (m) Torque T=FR (Nm) where: F =force on brake arm (N), R=brake radius (m).
3.10.4 Performance curves for internal combustion engines
3.10.4 Performance curves for internal combustion engines
Both four-stroke and two-stroke engines may have compression ignition instead of spark ignition. The air is compressed to a high pressure and temperature and the fuel injected. The high air temperature causes combustion.
Both four-stroke and two-stroke engines may have compression ignition instead of spark ignition. The air is compressed to a high pressure and temperature and the fuel injected. The high air temperature causes combustion.
MECHANICAL ENGINEER'S DATA HANDBOOK
MECHANICAL ENGINEER'S DATA HANDBOOK
Effect of mixture strength on p — v diagram
Effect of mixture strength on p — v diagram
pressures and the Roots blower and vane compressor are most suitable for low pressures.
pressures and the Roots blower and vane compressor are most suitable for low pressures.
The efficiency is increased by using more than one stage if intercooling is used between the stages to reduce ideally the temperature of the air to that at the first stage inlet. The cylinders become progressively smaller as the pressure increases and volume de- creases.
The efficiency is increased by using more than one stage if intercooling is used between the stages to reduce ideally the temperature of the air to that at the first stage inlet. The cylinders become progressively smaller as the pressure increases and volume de- creases.
For S stages, the ideal pressure for each stage is:
For S stages, the ideal pressure for each stage is:
3.12 Reciprocating air motor Reciprocating air motors are used extensively for tools such as breakers, picks, riveters, vibrators and drillers. They are useful where there is fire danger such as in coal mines. The operating cycle is the reverse of that for the reciprocating compressor.
3.12 Reciprocating air motor Reciprocating air motors are used extensively for tools such as breakers, picks, riveters, vibrators and drillers. They are useful where there is fire danger such as in coal mines. The operating cycle is the reverse of that for the reciprocating compressor.
If p,, p, and the under cooling temperature 7), are known, the diagram can be easily drawn and RE and W scaled off as shown. 3.13.3 Gas refrigeration cycle Referring to the 7-s diagram:
If p,, p, and the under cooling temperature 7), are known, the diagram can be easily drawn and RE and W scaled off as shown. 3.13.3 Gas refrigeration cycle Referring to the 7-s diagram:
3.14.4 Heat transfer from fins
3.14.4 Heat transfer from fins
Similar efficiency curves are given in the figures for straight fins of various shapes.
Similar efficiency curves are given in the figures for straight fins of various shapes.
Thermal conductivity coefficients (Wm 'K~') at 20°C and 1 bar
Thermal conductivity coefficients (Wm 'K~') at 20°C and 1 bar
3.14.5 Thermal conductivity coefficient
3.14.5 Thermal conductivity coefficient
MECHANICAL ENGINEER’S DATA HANDBOOK 3.14.6 Convection Convection is the transfer of heat in a fluid by the mixing of one part of the fluid with another. Motion of the fluid may be caused by differences in density due to temperature differences as in ‘natural convection’ (or ‘free convection’), or by mechanical means, such as pumping, as in ‘forced convection’.
MECHANICAL ENGINEER’S DATA HANDBOOK 3.14.6 Convection Convection is the transfer of heat in a fluid by the mixing of one part of the fluid with another. Motion of the fluid may be caused by differences in density due to temperature differences as in ‘natural convection’ (or ‘free convection’), or by mechanical means, such as pumping, as in ‘forced convection’.
MECHANICAL ENGINEER’S DATA HANDBOOK where: 7,=plate temperature, 7,=mean fluid tem- perature.
MECHANICAL ENGINEER’S DATA HANDBOOK where: 7,=plate temperature, 7,=mean fluid tem- perature.
Emissivity of surfaces (0-50°C except where stated)
Emissivity of surfaces (0-50°C except where stated)
3.15.2 Multi-pass and mixed-flow heat exchangers MECHANICAL ENGINEER’S DATA HANDBOOK
3.15.2 Multi-pass and mixed-flow heat exchangers MECHANICAL ENGINEER’S DATA HANDBOOK
The temperature range possible is greater than for the parallel-flow type. The same formulae apply.
The temperature range possible is greater than for the parallel-flow type. The same formulae apply.
3.15.3 Stearn condenser
3.15.3 Stearn condenser
be ‘weak’ or ‘lean’. With less air the combustion is incomplete and the mixture is said to be ‘rich’ (see table). 3.16.1 Air—fuel ratio and mixture strength The following deals with the combustion of solid, liquid and gaseous fuels with atmospheric air. The fuels are supposed to be composed only of carbon, hydrogen and sulphur, with perhaps oxygen and ash. The carbon, hydrogen and sulphur combine with the oxygen in the air; the nitrogen in the air remains unchanged. Definitions:
be ‘weak’ or ‘lean’. With less air the combustion is incomplete and the mixture is said to be ‘rich’ (see table). 3.16.1 Air—fuel ratio and mixture strength The following deals with the combustion of solid, liquid and gaseous fuels with atmospheric air. The fuels are supposed to be composed only of carbon, hydrogen and sulphur, with perhaps oxygen and ash. The carbon, hydrogen and sulphur combine with the oxygen in the air; the nitrogen in the air remains unchanged. Definitions:
MECHANICAL ENGINEER’S DATA HANDBOOK
MECHANICAL ENGINEER’S DATA HANDBOOK
Combustion products (% volume) 3.16.5 Hydrocarbon fuels, solid and liquid
Combustion products (% volume) 3.16.5 Hydrocarbon fuels, solid and liquid
Combustion products (% volume)
Combustion products (% volume)
MECHANICAL ENGINEER’S DATA HANDBOOK Air/fuel ratio from the CO, in the exhaust for fuel consisting of C and H, by weight
MECHANICAL ENGINEER’S DATA HANDBOOK Air/fuel ratio from the CO, in the exhaust for fuel consisting of C and H, by weight
MECHANICAL ENGINEER’S DATA HANDBOOK 3.16.9 Boiler efficiency This may be based on either the HCV or the LCV.
MECHANICAL ENGINEER’S DATA HANDBOOK 3.16.9 Boiler efficiency This may be based on either the HCV or the LCV.
Analysis of gaseous fuels
Analysis of gaseous fuels
A relatively small force F,, on the handle produces pressure in a small-diameter cylinder which acts on ¢ large-diameter cylinder to lift a large load W:
A relatively small force F,, on the handle produces pressure in a small-diameter cylinder which acts on ¢ large-diameter cylinder to lift a large load W:
The force on a submerged plate is equal to the pressure at the depth of its centroid multiplied by its area. The point at which the force acts is called the ‘centre of pressure’ and is at a greater depth than the centroid. A formula is also given for an angled plate.
The force on a submerged plate is equal to the pressure at the depth of its centroid multiplied by its area. The point at which the force acts is called the ‘centre of pressure’ and is at a greater depth than the centroid. A formula is also given for an angled plate.
Typical roughness of pipes For circular pipes only, the friction factor f= 16/Re. This value is independant of roughness.
Typical roughness of pipes For circular pipes only, the friction factor f= 16/Re. This value is independant of roughness.
Pressure loss p,;= Pr, = Pr = te. 4.2.6 Pressure loss in pipe fittings and Pipe section changes The pressure loss is the same in all pipes:
Pressure loss p,;= Pr, = Pr = te. 4.2.6 Pressure loss in pipe fittings and Pipe section changes The pressure loss is the same in all pipes:
In addition to pipe friction loss, there are losses due to changes in pipe cross-section and also due to fittings such as valves and filters. These losses are given in terms of velocity pressure p(V7/2) and a constant called the ‘K factor’.
In addition to pipe friction loss, there are losses due to changes in pipe cross-section and also due to fittings such as valves and filters. These losses are given in terms of velocity pressure p(V7/2) and a constant called the ‘K factor’.
MECHANICAL ENGINEER’S DATA HANDBOOK .3 Flow of liquids through various devices Flow in channels depends on the cross-section, the lope and the type of surface of the channel. Formulae are given for the flow through orifices, weirs and channels. Orifices are used for the measurement of flow, weirs being for channel flow.
MECHANICAL ENGINEER’S DATA HANDBOOK .3 Flow of liquids through various devices Flow in channels depends on the cross-section, the lope and the type of surface of the channel. Formulae are given for the flow through orifices, weirs and channels. Orifices are used for the measurement of flow, weirs being for channel flow.
These are used for measuring the flow of liquids and gases. In all three the restriction of flow creates a pressure difference which is measured to give an indication of the flow rate. The flow is always propor- tional to the square root of the pressure difference so that these two factors are non-linearly related. The venturi gives the least overall pressure loss (this is often important), but is much more expensive to make than the orifice which has a much greater loss. A good compromise is the pipe nozzle. The pressure difference may be measured by means of a manometer (as shown) or any other differential pressure device. ey ee a er , , ee ae The formula for flow rate is the same for each type. MECHANICAL ENGINEER’S DATA HANDBOOK
These are used for measuring the flow of liquids and gases. In all three the restriction of flow creates a pressure difference which is measured to give an indication of the flow rate. The flow is always propor- tional to the square root of the pressure difference so that these two factors are non-linearly related. The venturi gives the least overall pressure loss (this is often important), but is much more expensive to make than the orifice which has a much greater loss. A good compromise is the pipe nozzle. The pressure difference may be measured by means of a manometer (as shown) or any other differential pressure device. ey ee a er , , ee ae The formula for flow rate is the same for each type. MECHANICAL ENGINEER’S DATA HANDBOOK
is proportional to the mass flow rate. Examples are of jets striking both fixed and moving plates. If the velocity or direction of a jet of fluid is changed, there is a force on the device causing the change which
is proportional to the mass flow rate. Examples are of jets striking both fixed and moving plates. If the velocity or direction of a jet of fluid is changed, there is a force on the device causing the change which
MECHANICAL ENGINEER’S DATA HANDBOOK In the x direction: F, =pAV7(cos @, +cos 63) In the y direction: F,=pAV7(sin 6, —sin 6)
MECHANICAL ENGINEER’S DATA HANDBOOK In the x direction: F, =pAV7(cos @, +cos 63) In the y direction: F,=pAV7(sin 6, —sin 6)
This is an example of change in momentum of a fluic jet. The highest efficiency is obtained when the wate enters the boat in the direction of motion. When thi water enters the side of the boat, maximum efficienc:
This is an example of change in momentum of a fluic jet. The highest efficiency is obtained when the wate enters the boat in the direction of motion. When thi water enters the side of the boat, maximum efficienc:
Formulae are given for the compressible flow of a gas. They include isothermal flow with friction in a uniform pipe and flow through orifices. The velocity of sound in a gas is defined.
Formulae are given for the compressible flow of a gas. They include isothermal flow with friction in a uniform pipe and flow through orifices. The velocity of sound in a gas is defined.
Drag D=C,Ap > p=fluid density; A=frontal area; V=fluid velocity
Drag D=C,Ap > p=fluid density; A=frontal area; V=fluid velocity
MECHANICAL ENGINEER’S DATA HANDBOOK
MECHANICAL ENGINEER’S DATA HANDBOOK
Drag coefficients for various bodies (continued)
Drag coefficients for various bodies (continued)
Fluid enters the impeller axially at its centre of rotation through its ‘eye’ and is discharged from its rim in a spiralling motion having received energy from the rotating impeller. This results in an increase in both pressure and velocity. The kinetic energy is mostly converted to pressure energy in the volute and a tapered section of the discharge branch.
Fluid enters the impeller axially at its centre of rotation through its ‘eye’ and is discharged from its rim in a spiralling motion having received energy from the rotating impeller. This results in an increase in both pressure and velocity. The kinetic energy is mostly converted to pressure energy in the volute and a tapered section of the discharge branch.
where 9, = volumetric efficiency
where 9, = volumetric efficiency
where: K,=diffuser and volute discharge coefficient.
where: K,=diffuser and volute discharge coefficient.
Pump characteristics are plotted to a base of flow rate for a fixed pump speed. Head (or pressure), power and efficiency are plotted for different speeds to give a family of curves. For a given speed the point at which maximum efficiency is attained is called the ‘best efficiency point’ (B.E.P.). If the curves are plotted non-dimensionally a single curve is obtained which is also the same for all geometrically similar pumps.
Pump characteristics are plotted to a base of flow rate for a fixed pump speed. Head (or pressure), power and efficiency are plotted for different speeds to give a family of curves. For a given speed the point at which maximum efficiency is attained is called the ‘best efficiency point’ (B.E.P.). If the curves are plotted non-dimensionally a single curve is obtained which is also the same for all geometrically similar pumps.
Head (H), power (P) and efficiency (7) are plotted against flow at various speeds (N) and the B.E.P. can be determined from these. To give single curves for any speed the following non-dimensional quantities, (parameters) are plotted (see figure): Head parameter X,,=gH/N?D? Flow parameter X,=Q/ND? Power parameter X,=P/pN*D°
Head (H), power (P) and efficiency (7) are plotted against flow at various speeds (N) and the B.E.P. can be determined from these. To give single curves for any speed the following non-dimensional quantities, (parameters) are plotted (see figure): Head parameter X,,=gH/N?D? Flow parameter X,=Q/ND? Power parameter X,=P/pN*D°
Minimum safe suction head The theory for centrifugal fans is basically the same as that for centrifugal pumps but there are differences in construction since fans are used for gases and pumps for liquids. They are usually constructed from sheet metal and efficiency is sacrificed for simplicity. The three types are: the radial blade fan (paddle wheel fan); the backward-curved vane fan, which is similar in design to the centrifugal pump; and the forward- curved vane fan which has a wide impeller and a large number of vanes. Typical proportions for impellers, maximum efficiencies and static pressures are given together with the outlet-velocity diagram for the impeller.
Minimum safe suction head The theory for centrifugal fans is basically the same as that for centrifugal pumps but there are differences in construction since fans are used for gases and pumps for liquids. They are usually constructed from sheet metal and efficiency is sacrificed for simplicity. The three types are: the radial blade fan (paddle wheel fan); the backward-curved vane fan, which is similar in design to the centrifugal pump; and the forward- curved vane fan which has a wide impeller and a large number of vanes. Typical proportions for impellers, maximum efficiencies and static pressures are given together with the outlet-velocity diagram for the impeller.
It is useful to compare design parameters and charac- teristics of fluid machines for different sizes. This is done by introducing the concept of ‘specific speed’, which is a constant for geometrically similar machines.
It is useful to compare design parameters and charac- teristics of fluid machines for different sizes. This is done by introducing the concept of ‘specific speed’, which is a constant for geometrically similar machines.
MECHANICAL ENGINEER’S DATA HANDBOOK F, is constant over normal range of cutting speed. F, increases slowly with cutting speed.
MECHANICAL ENGINEER’S DATA HANDBOOK F, is constant over normal range of cutting speed. F, increases slowly with cutting speed.
F, and F, fall slowly with rake angle.
F, and F, fall slowly with rake angle.
Torning cutting speeds (m min~ |
Torning cutting speeds (m min~ |
F,, increases linearly with feed rate. F, increases in a curve with decreasing rate.
F,, increases linearly with feed rate. F, increases in a curve with decreasing rate.
2.8 Typical standard times for capstan and turret lathe operations 5.2.9 Lathe-tool nomenclature and setting Tool features For cutting to take place the tool must have a ‘front clearance angle’ which must not be so large that the tool is weakened. There must also be a ‘top rake angle’ to increase the effectiveness of cutting. The value of this angle depends on the material being cut. Typical values are given in the following table. There are many types of lathe tool, the principal ones being: bar turning; turning and facing; parting-off; facing; boring; and screw cutting. Some are made from a bar of tool steel, others with high-speed steel tips welded to carbon steel shanks and some with tungsten carbide tips brazed to a steel shank. A tool holder with interchangeable tips can also be used.
2.8 Typical standard times for capstan and turret lathe operations 5.2.9 Lathe-tool nomenclature and setting Tool features For cutting to take place the tool must have a ‘front clearance angle’ which must not be so large that the tool is weakened. There must also be a ‘top rake angle’ to increase the effectiveness of cutting. The value of this angle depends on the material being cut. Typical values are given in the following table. There are many types of lathe tool, the principal ones being: bar turning; turning and facing; parting-off; facing; boring; and screw cutting. Some are made from a bar of tool steel, others with high-speed steel tips welded to carbon steel shanks and some with tungsten carbide tips brazed to a steel shank. A tool holder with interchangeable tips can also be used.
MECHANICAL ENGINEER’S DATA HANDBOOK
MECHANICAL ENGINEER’S DATA HANDBOOK
Another feature is the ‘chip breaker’ which breaks long, dangerous and inconvenient streamers of ‘swarf’ into chips.
Another feature is the ‘chip breaker’ which breaks long, dangerous and inconvenient streamers of ‘swarf’ into chips.
Rake angle for different workpiece materials
Rake angle for different workpiece materials
In addition to front clearance and top rake, there are side clearance and side rake. A small nose radius improves cutting and reduces wear.
In addition to front clearance and top rake, there are side clearance and side rake. A small nose radius improves cutting and reduces wear.
The tool must not be set too high or too low, or inclined at an angle. The effects are shown in the figure. Tool setting This is used for ‘parting-off” the workpiece from bar stock held in a chuck. Note that there is ‘body clearance’ on both sides as well as ‘side cledrance’. The tool is weak and must be used with care. It must be set on or slightly above centre. If set even slightly below centre the work will climb onto the tool before parting-off.
The tool must not be set too high or too low, or inclined at an angle. The effects are shown in the figure. Tool setting This is used for ‘parting-off” the workpiece from bar stock held in a chuck. Note that there is ‘body clearance’ on both sides as well as ‘side cledrance’. The tool is weak and must be used with care. It must be set on or slightly above centre. If set even slightly below centre the work will climb onto the tool before parting-off.
Core drills have three or four flutes and are used for opening out existing holes, e.g. core holes in castings.
Core drills have three or four flutes and are used for opening out existing holes, e.g. core holes in castings.
Drilling plastics, cutting speeds and feeds
Drilling plastics, cutting speeds and feeds
*Speed = xDN/60000ms~', where D=diameter (mm), N=number of revolutions per minute. MECHANICAL ENGINEER’S DATA HANDBOOK
*Speed = xDN/60000ms~', where D=diameter (mm), N=number of revolutions per minute. MECHANICAL ENGINEER’S DATA HANDBOOK
Tapping drill sizes for metric coarse threads
Tapping drill sizes for metric coarse threads
Cutting lubricants for drilling, reaming and tapping
Cutting lubricants for drilling, reaming and tapping
MECHANICAL ENGINEER’S DATA HANDBOOK
MECHANICAL ENGINEER’S DATA HANDBOOK
Milling cutting speeds for high-speed steel cutters
Milling cutting speeds for high-speed steel cutters
Milling cutting speeds at a feed rate of 0.2mm per tooth
Milling cutting speeds at a feed rate of 0.2mm per tooth
Typical values of feed per tooth (mm) HSS, high-speed steels. These values should be lowered for finishing and increased for rough milling. where: f=feed/tooth (mm), z=number of teeth, N=number of revolutions per minute of cutter.
Typical values of feed per tooth (mm) HSS, high-speed steels. These values should be lowered for finishing and increased for rough milling. where: f=feed/tooth (mm), z=number of teeth, N=number of revolutions per minute of cutter.
5.5.1 Grinding machines
5.5.1 Grinding machines
MECHANICAL ENGINEER’S DATA HANDBOOK
MECHANICAL ENGINEER’S DATA HANDBOOK
Carbon steels (for softer metals and wood; poor performance above 250°C)
Carbon steels (for softer metals and wood; poor performance above 250°C)
Ceramic tools (sintered aluminium oxide with grain refiners and binder) Carbides are graded according to series (see table) and by a number from 01 (hardest) to 50 (toughest), e.g. PO! and K40. 5.6.7 Carbide and ceramic tools
Ceramic tools (sintered aluminium oxide with grain refiners and binder) Carbides are graded according to series (see table) and by a number from 01 (hardest) to 50 (toughest), e.g. PO! and K40. 5.6.7 Carbide and ceramic tools
R, rough; F, fine; R & T, reaming and threading; D, drilling. 7 General information on metal cutting
R, rough; F, fine; R & T, reaming and threading; D, drilling. 7 General information on metal cutting
5.7.5 Machining properties of thermoplastics
5.7.5 Machining properties of thermoplastics
Cutting fluid applications It is necessary when machining to use some form of fluid which acts as a coolant and lubricant, resulting in a better finish and longer tool life. The fluid also acts as a rust preventative and assists in swarf removal. The foliowing table lists various fluids and their advan- tages.
Cutting fluid applications It is necessary when machining to use some form of fluid which acts as a coolant and lubricant, resulting in a better finish and longer tool life. The fluid also acts as a rust preventative and assists in swarf removal. The foliowing table lists various fluids and their advan- tages.
MECHANICAL ENGINEER’S DATA HANDBOOK
MECHANICAL ENGINEER’S DATA HANDBOOK
removing it from the mould. Further processing is usually required.
removing it from the mould. Further processing is usually required.
This is a form of sand casting done using a very fine sand mixed with synthetic resin. The pattern is made of machined and polished iron. The sand mixture is blown into a box containing the pattern which is heated to produce a hard, thin (6-10mm) mould which is split and removed from the pattern and then glued together. It is a high-speed process, producing highly accurate castings.
This is a form of sand casting done using a very fine sand mixed with synthetic resin. The pattern is made of machined and polished iron. The sand mixture is blown into a box containing the pattern which is heated to produce a hard, thin (6-10mm) mould which is split and removed from the pattern and then glued together. It is a high-speed process, producing highly accurate castings.
Wax patterns are made from a permanent metal mould. The wax patterns are coated with ceramic slurry which is hardened and baked so that the wax is melted out. The cavity is filled with molten metal to give a precision casting. Any metal can be cast using this process.
Wax patterns are made from a permanent metal mould. The wax patterns are coated with ceramic slurry which is hardened and baked so that the wax is melted out. The cavity is filled with molten metal to give a precision casting. Any metal can be cast using this process.
The mould is of steel in several parts dowelled together. Molten metal is fed by gravity or pressure and, when solid, is ejected by pins. Aluminium, copper, manganese and zinc alloy are suitable for casting by this method.
The mould is of steel in several parts dowelled together. Molten metal is fed by gravity or pressure and, when solid, is ejected by pins. Aluminium, copper, manganese and zinc alloy are suitable for casting by this method.
Forging with flash removed
Forging with flash removed
MECHANICAL ENGINEER'S DATA HANDBOOK
MECHANICAL ENGINEER'S DATA HANDBOOK
A metal which is plastic when cold may be extruded by the impact of a high-velocity punch. The metal of the blank flows up the sides of the punch to produce a cylinder. The process is used for manufacturing tooth- paste tubes, ignition coil cans, etc.
A metal which is plastic when cold may be extruded by the impact of a high-velocity punch. The metal of the blank flows up the sides of the punch to produce a cylinder. The process is used for manufacturing tooth- paste tubes, ignition coil cans, etc.
Soft metals such as aluminium and copper can be extruded cold. Practically all metals may be extruded.
Soft metals such as aluminium and copper can be extruded cold. Practically all metals may be extruded.
Dx B from 25mm x 25mm to 200mm x 200 mm. Several values of t in each case.
Dx B from 25mm x 25mm to 200mm x 200 mm. Several values of t in each case.
Dx B=152mm x 152mm to 356mm x 406 mm. t and T are in several sizes in each case.
Dx B=152mm x 152mm to 356mm x 406 mm. t and T are in several sizes in each case.
Dx B from 40mm x 25mm to 200mm x 150mm. Unequal angles
Dx B from 40mm x 25mm to 200mm x 150mm. Unequal angles
5.10 Soldering and brazing
5.10 Soldering and brazing
Above about 800°C the process is called ‘brazing’ (or hard soldering). Brazing rod (50% copper and 50% zinc) is used for general work, with a flux consisting of borax mixed to a paste with water. A torch supplied with mains gas and compressed air is used. Taps control the flow and mixture. For large-scale produc- tion work, induction and furnace heating are used.
Above about 800°C the process is called ‘brazing’ (or hard soldering). Brazing rod (50% copper and 50% zinc) is used for general work, with a flux consisting of borax mixed to a paste with water. A torch supplied with mains gas and compressed air is used. Taps control the flow and mixture. For large-scale produc- tion work, induction and furnace heating are used.
A torch mixes the gases which issue from a copper nozzle designed to suit the weld size. The process produces harmful radiation and goggles must be worn. The process is suitable for steel plate up to 25mm thick, but is mostly used for plate about 2mm thick.
A torch mixes the gases which issue from a copper nozzle designed to suit the weld size. The process produces harmful radiation and goggles must be worn. The process is suitable for steel plate up to 25mm thick, but is mostly used for plate about 2mm thick.
MECHANICAL ENGINEER’S DATA HANDBOOK 5.11.2 Type of flame duces brittle low-strength oxides. Use of this flame should be avoided when welding brass and bronze. It is essential to have the correct type of flame which depends on the proportions of the gases.
MECHANICAL ENGINEER’S DATA HANDBOOK 5.11.2 Type of flame duces brittle low-strength oxides. Use of this flame should be avoided when welding brass and bronze. It is essential to have the correct type of flame which depends on the proportions of the gases.
Leftward welding Two methods of gas welding are used: leftward and rightward. 5.11.3 Method of gas welding
Leftward welding Two methods of gas welding are used: leftward and rightward. 5.11.3 Method of gas welding
The table below gives recommended filler rod ma- terials and fluxes for gas welding.
The table below gives recommended filler rod ma- terials and fluxes for gas welding.
Oxyacetylene cutting
Oxyacetylene cutting
The plate is first heated by a mixture of oxygen and acetylene until red hot and then a stream of oxygen alone is used to burn with the metal with intense heat. Propane and butane may be used with plain carbon steel, but are not as effective as oxygen. Cutting speeds of up to 280 mm min“! are possible with 25-mm plate. Typical speeds are given in the table. Steel plate over 300mm thick can be cut by this method, either manually or by automatic machine using templates for complicated shapes. Thin plates may be stacked so that many may be cut at one time.
The plate is first heated by a mixture of oxygen and acetylene until red hot and then a stream of oxygen alone is used to burn with the metal with intense heat. Propane and butane may be used with plain carbon steel, but are not as effective as oxygen. Cutting speeds of up to 280 mm min“! are possible with 25-mm plate. Typical speeds are given in the table. Steel plate over 300mm thick can be cut by this method, either manually or by automatic machine using templates for complicated shapes. Thin plates may be stacked so that many may be cut at one time.
MECHANICAL ENGINEER’S DATA HANDBOOK
MECHANICAL ENGINEER’S DATA HANDBOOK
R=recommended; S=satisfactory; N=not recommended; U =unsuitable. MECHANICAL ENGINEER’S DATA HANDBOOK
R=recommended; S=satisfactory; N=not recommended; U =unsuitable. MECHANICAL ENGINEER’S DATA HANDBOOK
Are welding — edge preparation
Are welding — edge preparation
Effective throat size (¢= throat thickness, L =leg length) The relevant British Standards are BS 4360: Part 2, BS 639, BS 1719, BS 1856, BS 2642, BS 449 and BS 499. 5.12.9 Welding terminology, throat size and allowable stress
Effective throat size (¢= throat thickness, L =leg length) The relevant British Standards are BS 4360: Part 2, BS 639, BS 1719, BS 1856, BS 2642, BS 449 and BS 499. 5.12.9 Welding terminology, throat size and allowable stress
5.13.1 Terminology It is impossible to make components the exact size and an allowance or ‘tolerance’ must be made which depends on the process and the application. The tolerance results in two extremes of size which must be maintained. The tolerances of two fitting parts, e.g. a shaft in a bearing, determines the type of ‘fit? and British Standard BS 4500: Part 1: 1969, ‘ISO Limits and Fits’, gives a comprehensive system relating to holes and shafts; it can, however, be used for other components, e.g. a key in a keyway.
5.13.1 Terminology It is impossible to make components the exact size and an allowance or ‘tolerance’ must be made which depends on the process and the application. The tolerance results in two extremes of size which must be maintained. The tolerances of two fitting parts, e.g. a shaft in a bearing, determines the type of ‘fit? and British Standard BS 4500: Part 1: 1969, ‘ISO Limits and Fits’, gives a comprehensive system relating to holes and shafts; it can, however, be used for other components, e.g. a key in a keyway.
Reduced range of fits for conventionally manufactured parts 5.13.3 Example of symbols and sizes on drawing BS 4500 gives 18 ‘tolerance grades’ numbered ITO1, ITO, IT1, IT2, up to IT(6. The actual tolerance depends on the size of the component (see table below).
Reduced range of fits for conventionally manufactured parts 5.13.3 Example of symbols and sizes on drawing BS 4500 gives 18 ‘tolerance grades’ numbered ITO1, ITO, IT1, IT2, up to IT(6. The actual tolerance depends on the size of the component (see table below).
On the drawing these parameters would be given as {rounding off to nearest 0.01 mm):
On the drawing these parameters would be given as {rounding off to nearest 0.01 mm):
Properties of some grey irons (BS 1452) *BHN =Brinell hardness number. silicon plus manganese, sulphur and phosphorus. It is brittle with low tensile strength, but is easy to cast. Grey iron is so called because of the colour of the fracture face. It contains 1.5-4.3% carbon and 0.3-5% 6.1.2 Spheroidal graphite (SG) iron
Properties of some grey irons (BS 1452) *BHN =Brinell hardness number. silicon plus manganese, sulphur and phosphorus. It is brittle with low tensile strength, but is easy to cast. Grey iron is so called because of the colour of the fracture face. It contains 1.5-4.3% carbon and 0.3-5% 6.1.2 Spheroidal graphite (SG) iron
Properties of some SG irons (BS 2789) *BH =Brinell hardness number. proved further by heat treatment. Mechanical proper- ties approach those of steel combined with good castability.
Properties of some SG irons (BS 2789) *BH =Brinell hardness number. proved further by heat treatment. Mechanical proper- ties approach those of steel combined with good castability.
Properties of some malleable irons *BHN =Brinell hardness number. These have excellent machining qualities with strength similar to grey irons but better ductility as a result of closely controlled heat treatment. There are three types: white heart with superior casting properties; 6.1.4 Alloy irons black heart with superior machining properties; and pearlitic which is superior to the other two but difficult to produce.
Properties of some malleable irons *BHN =Brinell hardness number. These have excellent machining qualities with strength similar to grey irons but better ductility as a result of closely controlled heat treatment. There are three types: white heart with superior casting properties; 6.1.4 Alloy irons black heart with superior machining properties; and pearlitic which is superior to the other two but difficult to produce.
Properties of carbon steels (BS 970) MECHANICAL ENGINEER'S DATA HANDBOOK
Properties of carbon steels (BS 970) MECHANICAL ENGINEER'S DATA HANDBOOK
Alloy steels differ from carbon steels in that they contain a high proportion of other alloying elements. The following are regarded as the minimum levels:
Alloy steels differ from carbon steels in that they contain a high proportion of other alloying elements. The following are regarded as the minimum levels:
Tempering temperature and colour for carbon steels *BHN =Brinell hardness number. +To BS 950.
Tempering temperature and colour for carbon steels *BHN =Brinell hardness number. +To BS 950.
Properties of carbon steels (BS 970) (continued)
Properties of carbon steels (BS 970) (continued)
Typical properties of alloy steels A=ausformed, MA = martempered, CR = cold rolled, P = poor, F = fair, G= good, PH = preheat required, PR = protection required, HT = at high temperature, HTR = when heat treated, FHTR = final heat treatment required.
Typical properties of alloy steels A=ausformed, MA = martempered, CR = cold rolled, P = poor, F = fair, G= good, PH = preheat required, PR = protection required, HT = at high temperature, HTR = when heat treated, FHTR = final heat treatment required.
Mechanical properties of weldable structural steel for hollow sections (BS 4360: 1972) *Up to 16mm thickness.
Mechanical properties of weldable structural steel for hollow sections (BS 4360: 1972) *Up to 16mm thickness.
MECHANICAL ENGINEER’S DATA HANDBOOK 6.3.6 Weldable structural steel for hollow sections
MECHANICAL ENGINEER’S DATA HANDBOOK 6.3.6 Weldable structural steel for hollow sections
S=softened, H=hardened, AD=as drawn, AH =air hardened.
S=softened, H=hardened, AD=as drawn, AH =air hardened.
Composition and mechanical properties of some copper alloys
Composition and mechanical properties of some copper alloys
Composition and mechanical properties of some copper alloys (continued) Applications of copper and copper alloys
Composition and mechanical properties of some copper alloys (continued) Applications of copper and copper alloys
= annealed, M=as manufactured, H=fully work hardened, WP =solution heat treated and precipitation hardened MECHANICAL ENGINEER’S DATA HANDBOOK 6.6.2 Aluminium and aluminium alloys
= annealed, M=as manufactured, H=fully work hardened, WP =solution heat treated and precipitation hardened MECHANICAL ENGINEER’S DATA HANDBOOK 6.6.2 Aluminium and aluminium alloys
Aluminium alloys may be classified as follows.
Aluminium alloys may be classified as follows.
O=annealed, }H=haif hard, H=fully work hardened, M=as manufactured, W=solution treated only, WP =solution treated and precipitation hardened, T=solution heat treated and naturally aged. MECHANICAL ENGINEER’S DATA HANDBOOK
O=annealed, }H=haif hard, H=fully work hardened, M=as manufactured, W=solution treated only, WP =solution treated and precipitation hardened, T=solution heat treated and naturally aged. MECHANICAL ENGINEER’S DATA HANDBOOK
6.8.4 Moduli of spring materials
6.8.4 Moduli of spring materials
6.9.1 Process Powdered metal technology is used widely to produce components which are homogeneous, have controlled density, are inclusion free and of uniform strength.
6.9.1 Process Powdered metal technology is used widely to produce components which are homogeneous, have controlled density, are inclusion free and of uniform strength.
Physical properties of common engineering materials
Physical properties of common engineering materials
PS/YS=proof stress (Nmm~?)/yield stress (Nmm~?), E=Young’s modulus, G=shear modulus, v=Poisson’s ratio, «=coefficient of linear expansion, p=density. *Do not obey Hooke’s law. MECHANICAL ENGINEER'S DATA HANDBOOK
PS/YS=proof stress (Nmm~?)/yield stress (Nmm~?), E=Young’s modulus, G=shear modulus, v=Poisson’s ratio, «=coefficient of linear expansion, p=density. *Do not obey Hooke’s law. MECHANICAL ENGINEER'S DATA HANDBOOK
Comparison of hardness numbers
Comparison of hardness numbers
Typical Brinell hardness numbers (BHN) for metals
Typical Brinell hardness numbers (BHN) for metals
Chemical symbols for metals and alloying elements
Chemical symbols for metals and alloying elements
m.p.= melting point, p=density, E= Young’s modulus, G =shear modulus, RSHC = relative specific heat capacity, a=coefficient of linear expansion, p,=resistivity at 0°C, «,=resistance temperature coefficient at 0°C, ECE = electrochemical equivalent. MECHANICAL ENGINEER'S DATA HANDBOOK
m.p.= melting point, p=density, E= Young’s modulus, G =shear modulus, RSHC = relative specific heat capacity, a=coefficient of linear expansion, p,=resistivity at 0°C, «,=resistance temperature coefficient at 0°C, ECE = electrochemical equivalent. MECHANICAL ENGINEER'S DATA HANDBOOK
Environments causing stress corrosion cracking 6.12.4 Galvanic corrosion
Environments causing stress corrosion cracking 6.12.4 Galvanic corrosion
Galvanic table for pure metals (relative to hydrogen)
Galvanic table for pure metals (relative to hydrogen)
Typical physical properties of plastics BHN = Brinell hardness number, p=density, E = Young’s modulus.
Typical physical properties of plastics BHN = Brinell hardness number, p=density, E = Young’s modulus.
Relative properties of plastics
Relative properties of plastics
O=outstanding, E=excellent, G=good, F =fair, P=poor. Tensile strength (typical): E=55 Nmm7~?; P=21 Nmm_~?. Compressive strength (typical): E=210 Nmm~?; P=35Nmm_7"?. MECHANICAL ENGINEER'S DATA HANDBOOK
O=outstanding, E=excellent, G=good, F =fair, P=poor. Tensile strength (typical): E=55 Nmm7~?; P=21 Nmm_~?. Compressive strength (typical): E=210 Nmm~?; P=35Nmm_7"?. MECHANICAL ENGINEER'S DATA HANDBOOK
Mechanical properties of timbers
Mechanical properties of timbers
Permitted stresses in structural timbers (N mm”)
Permitted stresses in structural timbers (N mm”)
6.16.6 Maximum and minimum service temperatures for adhesives
6.16.6 Maximum and minimum service temperatures for adhesives
Arrangement of fibres in composites
Arrangement of fibres in composites
MECHANICAL ENGINEER’S DATA HANDBOOK 6.17.4 Matrix materials for composites Polymers: epoxies, polyesters, phenolics, silicones, polyimides, and other high-temperature polymers.
MECHANICAL ENGINEER’S DATA HANDBOOK 6.17.4 Matrix materials for composites Polymers: epoxies, polyesters, phenolics, silicones, polyimides, and other high-temperature polymers.
Typical cermets and applications (continued) .20 Materials for special requirements
Typical cermets and applications (continued) .20 Materials for special requirements
High temperature metals
High temperature metals
High strength-to-weight ratio materials Suspended absorbers Perforated panels with absorbent backing
High strength-to-weight ratio materials Suspended absorbers Perforated panels with absorbent backing
Miscellaneous solids MECHANICAL ENGINEER'S DATA HANDBOOK
Miscellaneous solids MECHANICAL ENGINEER'S DATA HANDBOOK
Coefficients of linear expansion «(x 10°°C~') at normal temperature (unless otherwise stated)
Coefficients of linear expansion «(x 10°°C~') at normal temperature (unless otherwise stated)
These consist of a number of thin blades of spring steel of exact, various thicknesses. They are used for measuring small gaps between parts. Micrometers are used for the measurement of internal and external dimensions, particularly of cylindrical shape. Measurement is based on the advance of a precision screw. The ‘outside micrometer’ is made in a variety of sizes, the most popular being 25mm in 0.01-mm steps. It has a fixed ‘barrel’ graduated in
These consist of a number of thin blades of spring steel of exact, various thicknesses. They are used for measuring small gaps between parts. Micrometers are used for the measurement of internal and external dimensions, particularly of cylindrical shape. Measurement is based on the advance of a precision screw. The ‘outside micrometer’ is made in a variety of sizes, the most popular being 25mm in 0.01-mm steps. It has a fixed ‘barrel’ graduated in
These are made from hardened and tempered steel marked off with high accuracy in lengths from about 10-30.cm with folding rules up to 60. cm. They are used for marking off, setting callipers and dividers, etc. When used directly, the accuracy is +0.25mm, and when used to set a scribing block the accuracy is +0.125mm.
These are made from hardened and tempered steel marked off with high accuracy in lengths from about 10-30.cm with folding rules up to 60. cm. They are used for marking off, setting callipers and dividers, etc. When used directly, the accuracy is +0.25mm, and when used to set a scribing block the accuracy is +0.125mm.
This is used for internal and external measurement. It has a long flat scale with a fixed jaw and a sliding jaw, with a scale, or cursor, sliding along the fixed scale and read in conjunction with it. Two scales are provided to allow measurement inside or outside of the jaws. Reading on main scale=43.5mm Reading on cursor=0.18 mm Total reading = 43.68 mm
This is used for internal and external measurement. It has a long flat scale with a fixed jaw and a sliding jaw, with a scale, or cursor, sliding along the fixed scale and read in conjunction with it. Two scales are provided to allow measurement inside or outside of the jaws. Reading on main scale=43.5mm Reading on cursor=0.18 mm Total reading = 43.68 mm
{-mm and 0.5-mm divisions screwed with a 0.5mm pitch thread and a ‘thimble’ graduated around its circumference with 50-0.01 mm divisions. An ‘inside micrometer’ has the fixed anvil projecting from the thimble; extensions may be attached. A ‘micrometer head’ is available consisting of the barrel and thimble assembly for use in any precision measur- ing device.
{-mm and 0.5-mm divisions screwed with a 0.5mm pitch thread and a ‘thimble’ graduated around its circumference with 50-0.01 mm divisions. An ‘inside micrometer’ has the fixed anvil projecting from the thimble; extensions may be attached. A ‘micrometer head’ is available consisting of the barrel and thimble assembly for use in any precision measur- ing device.
The linear movement of a spring-loaded plunger is magnified by gears and displayed on a dial. Various sensitivities are available and a smaller scale shows complete revolutions of the main pointer. A typical indicator has a scale with 100—0.01 mm divisions and a small dial reading up to 25 revolutions of the pointer, i.e. a total range of 25mm.
The linear movement of a spring-loaded plunger is magnified by gears and displayed on a dial. Various sensitivities are available and a smaller scale shows complete revolutions of the main pointer. A typical indicator has a scale with 100—0.01 mm divisions and a small dial reading up to 25 revolutions of the pointer, i.e. a total range of 25mm.
The following table gives the accuracy of different methods of linear measurement.
The following table gives the accuracy of different methods of linear measurement.
Gauge block sets (BS 888) Protective slips are provided for use at the ends of the combinations.
Gauge block sets (BS 888) Protective slips are provided for use at the ends of the combinations.
MECHANICAL ENGINEER'S DATA HANDBOOK
MECHANICAL ENGINEER'S DATA HANDBOOK
A typical extensometer (the Huggenberger) is shown. The knife edges A and B are held on to the specimen by a clamp with gauge length L. There are pivots at Cand D and knife edges E and F are held in contact by a tension spring. The magnified increase in L is indicated by a pointer H on a scale J. The commonest type of strain gauge is the electrical resistance strain gauge (‘strain gauge’ for short). These are devices which produce an electrical signa! propor- tional to the mechanical strain of the surface to which they are bonded. They can be made extremely small and can be attached to components of any shape which may be moving, e.g. an engine con-rod.
A typical extensometer (the Huggenberger) is shown. The knife edges A and B are held on to the specimen by a clamp with gauge length L. There are pivots at Cand D and knife edges E and F are held in contact by a tension spring. The magnified increase in L is indicated by a pointer H on a scale J. The commonest type of strain gauge is the electrical resistance strain gauge (‘strain gauge’ for short). These are devices which produce an electrical signa! propor- tional to the mechanical strain of the surface to which they are bonded. They can be made extremely small and can be attached to components of any shape which may be moving, e.g. an engine con-rod.
bridge circuit and the strain is measured by a gal- vanometer or calibrated resistor. Dynamic strains may be indicated on an oscilloscope or suitable recorder. It is usually necessary to use ‘dummy’ gauges mounted on an unstressed surface at the same temperature to compensate for temperature effects. The sensitivity of a strain gauge is given by the ‘gauge factor’, i.e. the ratio of change in resistance to gauge resistance divided by the strain. Various ar- rangements are used, depending on the type of stress being measured, e.g. tension, compression, bending and torsion. For two-dimensional stress situations a ‘strain gauge rosette’ consisting of three gauges at different angles is used. The principal stresses and their direction can be calculated from the three strains.
bridge circuit and the strain is measured by a gal- vanometer or calibrated resistor. Dynamic strains may be indicated on an oscilloscope or suitable recorder. It is usually necessary to use ‘dummy’ gauges mounted on an unstressed surface at the same temperature to compensate for temperature effects. The sensitivity of a strain gauge is given by the ‘gauge factor’, i.e. the ratio of change in resistance to gauge resistance divided by the strain. Various ar- rangements are used, depending on the type of stress being measured, e.g. tension, compression, bending and torsion. For two-dimensional stress situations a ‘strain gauge rosette’ consisting of three gauges at different angles is used. The principal stresses and their direction can be calculated from the three strains.
Bending (four active gauges: two in tension, two in compression)
Bending (four active gauges: two in tension, two in compression)
Tension or compression (one active gauge, one dummy gauge) Bending (two active gauges: one in tension, one in compression)
Tension or compression (one active gauge, one dummy gauge) Bending (two active gauges: one in tension, one in compression)
This arrangement eliminates the effect of bending.
This arrangement eliminates the effect of bending.
In the case of two-dimensional stress, it is necessary to use three gauges. If the gauges are at 45° to one another, then the principal stresses may be found as follows.
In the case of two-dimensional stress, it is necessary to use three gauges. If the gauges are at 45° to one another, then the principal stresses may be found as follows.
G = galvanometer, C =cold junction, H = hot junction A bath of melting ice is used for the cold junction. Temperature is given relative to 0°C.
G = galvanometer, C =cold junction, H = hot junction A bath of melting ice is used for the cold junction. Temperature is given relative to 0°C.
Thermoelectric sensitivity of thermocouple materials relative to platinum (reference junction at 0°C)
Thermoelectric sensitivity of thermocouple materials relative to platinum (reference junction at 0°C)
7.4.4 Thermocouple pairs an temperature limit
7.4.4 Thermocouple pairs an temperature limit
This consists of a number of thermocouples connected in series to give a higher e.m/f.
This consists of a number of thermocouples connected in series to give a higher e.m/f.
Thermal e.m.f, for common thermocouple combinations (reference junction at 0°C)
Thermal e.m.f, for common thermocouple combinations (reference junction at 0°C)
Resistance temperature coefficients (at room temperature) °C™'
Resistance temperature coefficients (at room temperature) °C™'
The main disadvantages are fragility and slow esponse.
The main disadvantages are fragility and slow esponse.
Resistance tharmometer measuring bridge The construction of a typical resistance thermom- eter is shown in the figure. It consists of a small resistance coil enclosed in a metal sheath with ceramic insulation beads. The temperature range is 100°C to 300°C for nickel and 200°C to 800°C for platinum.
Resistance tharmometer measuring bridge The construction of a typical resistance thermom- eter is shown in the figure. It consists of a small resistance coil enclosed in a metal sheath with ceramic insulation beads. The temperature range is 100°C to 300°C for nickel and 200°C to 800°C for platinum.
The deflection of a bimetallic strip or coil may be used to indicate temperature. This type is not very accurate but is simple and cheap. These thermometers are used for alarms and temperature controllers when connec- ted to a mechanical system. 7.4.12. Temperature-sensitive paints
The deflection of a bimetallic strip or coil may be used to indicate temperature. This type is not very accurate but is simple and cheap. These thermometers are used for alarms and temperature controllers when connec- ted to a mechanical system. 7.4.12. Temperature-sensitive paints
The brightness and colour of a hot body varies with temperature and in the case of the disappearing filament pyrometer it is compared with the appearance of a heated lamp filament. The radiation is focused
The brightness and colour of a hot body varies with temperature and in the case of the disappearing filament pyrometer it is compared with the appearance of a heated lamp filament. The radiation is focused
7.6.5 Differential pressure flowmeters
7.6.5 Differential pressure flowmeters
Symbols are as for manometers (see above). The flow formula is as for the Venturi meter.
Symbols are as for manometers (see above). The flow formula is as for the Venturi meter.
7.6.4 Turbine flow meters This is a type of variable-orifice meter consisting of a vertical glass tapered tube containing a metal ‘float’. The fluid, which may be a liquid or gas, flows through the annular space between the float and the tube. As the flow is increased the float moves to a greater height. The movement is roughly proportional to flow, and calibration is usually carried our by the supplier. Angled grooves in the rim of the float cause rotation and give the float stability. An axial or tangential impeller mounted in a pipe rotates at a speed roughly proportional to the velocity, and hence the flow, of the fluid in the pipe. The rotational speed is measured either mechanically or electronically to give flow or flow rate.
7.6.4 Turbine flow meters This is a type of variable-orifice meter consisting of a vertical glass tapered tube containing a metal ‘float’. The fluid, which may be a liquid or gas, flows through the annular space between the float and the tube. As the flow is increased the float moves to a greater height. The movement is roughly proportional to flow, and calibration is usually carried our by the supplier. Angled grooves in the rim of the float cause rotation and give the float stability. An axial or tangential impeller mounted in a pipe rotates at a speed roughly proportional to the velocity, and hence the flow, of the fluid in the pipe. The rotational speed is measured either mechanically or electronically to give flow or flow rate.
7.7.1 Pitot-static tube The pitot-static tube consists of two concentric tubes, the central one with an open end pointing upstream of the fluid flow and the other closed at the end but with small holes drilled at right angles to the direction of flow. The central tube pressure is equal to the static pressure plus the ‘velocity pressure’, whereas the outer tube pressure is the static pressure only. large pipes or ducts, traversing gear is used and an average value of velocity calculated. A manometer or other differential pressure measur- ing device measures the pressure difference between the tubes which is equal to the ‘velocity pressure’. For
7.7.1 Pitot-static tube The pitot-static tube consists of two concentric tubes, the central one with an open end pointing upstream of the fluid flow and the other closed at the end but with small holes drilled at right angles to the direction of flow. The central tube pressure is equal to the static pressure plus the ‘velocity pressure’, whereas the outer tube pressure is the static pressure only. large pipes or ducts, traversing gear is used and an average value of velocity calculated. A manometer or other differential pressure measur- ing device measures the pressure difference between the tubes which is equal to the ‘velocity pressure’. For
7.8.1 Mechanical tachometers dicated as rotational speed on a meter. Alternatively, a toothed wheel passing an inductive pick-up generates pulses which are counted over a fixed time and displayed on a meter as the speed of rotation. These may be permanently mounted on a machine or hand-held. The hand-held type has several shaft attachments with rubber ends (see figure), including a conical end for use with a shaft centre hole, a wheel to run on a cylindrical surface, and a cup end for use where there is no centre hole. terminating in an extremely small heated wire element is situated in the fluid stream and cools to an extent which depends on the velocity. The resulting change in resistance of the element is measured by a bridge circuit and is related to velocity by calibration. The response is rapid. 7.8.3 Stroboscope This has an electronic flash tube which flashes at a variable rate and which is adjusted to coincide with the rotational speed so that the rotating object, or a suitable mark on it, appears to stand still. The flash-rate control is calibrated in rotational speed. 7.8.2 Electrical tachometers 7.7.2 Anemometers The tachogenerator is driven by the shaft and gives an output voltage proportional to speed which is in-
7.8.1 Mechanical tachometers dicated as rotational speed on a meter. Alternatively, a toothed wheel passing an inductive pick-up generates pulses which are counted over a fixed time and displayed on a meter as the speed of rotation. These may be permanently mounted on a machine or hand-held. The hand-held type has several shaft attachments with rubber ends (see figure), including a conical end for use with a shaft centre hole, a wheel to run on a cylindrical surface, and a cup end for use where there is no centre hole. terminating in an extremely small heated wire element is situated in the fluid stream and cools to an extent which depends on the velocity. The resulting change in resistance of the element is measured by a bridge circuit and is related to velocity by calibration. The response is rapid. 7.8.3 Stroboscope This has an electronic flash tube which flashes at a variable rate and which is adjusted to coincide with the rotational speed so that the rotating object, or a suitable mark on it, appears to stand still. The flash-rate control is calibrated in rotational speed. 7.8.2 Electrical tachometers 7.7.2 Anemometers The tachogenerator is driven by the shaft and gives an output voltage proportional to speed which is in-
MECHANICAL ENGINEER’S DATA HANDBOOK One of the most important tests is the tensile test, especially that for steel. Typical curves are shown for ductile steel and hard steel. In the case of a ductile steel such as ‘mild steel’, there is a definite yield point above which the steel is no longer elastic. In the case of hard steel the load—extension curve becomes non-linear and it is necessary to specify a ‘proof stress’ for a specified strain, e.g. 0.1%.
MECHANICAL ENGINEER’S DATA HANDBOOK One of the most important tests is the tensile test, especially that for steel. Typical curves are shown for ductile steel and hard steel. In the case of a ductile steel such as ‘mild steel’, there is a definite yield point above which the steel is no longer elastic. In the case of hard steel the load—extension curve becomes non-linear and it is necessary to specify a ‘proof stress’ for a specified strain, e.g. 0.1%.
8.1.5 Si equivalents for Imperial and US customary units Abbreviations used
8.1.5 Si equivalents for Imperial and US customary units Abbreviations used
MECHANICAL ENGINEER’S DATA HANDBOOK
MECHANICAL ENGINEER’S DATA HANDBOOK
The term ‘screw’ is applied to a wide range of threaded fasteners used with metal, wood, plastics, etc. Screws have a variety of types of head and are made in many materials (steel, brass, nylon, etc.), some are plated. Small screws usually have BA threads and special threads are used for wood and self-tapping screws. Screws
The term ‘screw’ is applied to a wide range of threaded fasteners used with metal, wood, plastics, etc. Screws have a variety of types of head and are made in many materials (steel, brass, nylon, etc.), some are plated. Small screws usually have BA threads and special threads are used for wood and self-tapping screws. Screws
MECHANICAL ENGINEER'S DATA HANDBOOK
MECHANICAL ENGINEER'S DATA HANDBOOK
Rivets are used to make permanent joints between two or more plates. Steel rivets may be closed when red hot; rivets of softer metals such as aluminium and copper may be closed cold. There are a number of types of riveted joint configurations for plates, two of which are shown in the figure.
Rivets are used to make permanent joints between two or more plates. Steel rivets may be closed when red hot; rivets of softer metals such as aluminium and copper may be closed cold. There are a number of types of riveted joint configurations for plates, two of which are shown in the figure.
tight fit. Split pins are used mainly for locking nuts. Cotter pins are used to connect rods in tension and fits into mating slots. tight fit. Split pins are used mainly for locking nuts. Cotter pins are used to connect rods in tension and fits into mating slots.
tight fit. Split pins are used mainly for locking nuts. Cotter pins are used to connect rods in tension and fits into mating slots. tight fit. Split pins are used mainly for locking nuts. Cotter pins are used to connect rods in tension and fits into mating slots.
Pins
Pins
ISO metric precision hexagon nuts and bolts (all quantities) (in mm) 8.2.4 ISO metric nut and bolt sizes
ISO metric precision hexagon nuts and bolts (all quantities) (in mm) 8.2.4 ISO metric nut and bolt sizes
Clearance holes for metric bolts
Clearance holes for metric bolts
BSP pipe threads (BS 2779: 1973) — Whitworth thread form
BSP pipe threads (BS 2779: 1973) — Whitworth thread form
BSP pipe threads (BS 2779: 1973) — Whitworth thread form (continued) MECHANICAL ENGINEER'S DATA HANDBOOK
BSP pipe threads (BS 2779: 1973) — Whitworth thread form (continued) MECHANICAL ENGINEER'S DATA HANDBOOK
Dimensions (mm)
Dimensions (mm)
8.3.1 Circular, square and rectangular hollow steel sections MECHANICAL ENGINEER’S DATA HANDBOOK
8.3.1 Circular, square and rectangular hollow steel sections MECHANICAL ENGINEER’S DATA HANDBOOK
*Not to BS 4848: Part 2.
*Not to BS 4848: Part 2.
*Not to BS 4848: Part 2. MECHANICAL ENGINEER’S DATA HANDBOOK
*Not to BS 4848: Part 2. MECHANICAL ENGINEER’S DATA HANDBOOK
*Outer diameter. Size are given in BS 2871: Part 1. 8.3.3 Copper pipe sizes for domestic water pipes, etc.
*Outer diameter. Size are given in BS 2871: Part 1. 8.3.3 Copper pipe sizes for domestic water pipes, etc.
Typical factors of safety for various materials
Typical factors of safety for various materials

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