An Introduction To Pin Types , Application And Calculation
Introduction
The oldest mechanical fastener is undoubtedly the pin A pin is a machine element or fastening component or device that secures the positions of two or more parts relative to one another in a structure or assembly by passing through holes in those parts. Pins usually remain fixed in place by
the friction caused by interference between the pin’s surface and the material surrounding it in the part(s) into which it is inserted.
This friction force is the result of the microscopic asperities on the surface of the pin (whatever material it is made of) and on the surface of the hole surrounding the pin (whatever material those parts are made of)
Any squeezing force from the material into which the pin is installed causes the friction force to be higher. A squeezing force results from the material surrounding the pin pushing back on the pin in
its attempt to recover the elastic portion of the deformation forced upon it by insertion of the pin. However, there are also pins that must be held in place axially to allow intentional radial motion (e.g., rotation of one part relative to another or, at least, to the pin). Pins often have neither heads nor feet and, consequently, are incapable of developing any clamping force. They are intended to operate in shear by bearing against the material into which they are inserted.
Cross pin in rod and sleeve.
Pin shearing stress:
Pressure on rod:
Pressure on sleeve:
where:
F .... acting force [N, lb]
D .... rod diameter [mm, in]
D1 ... sleeve diameter [mm, in]
d .... pin diameter [mm, in]
i ..... number of pins
KL ... load distribution factor
KSb, KSp ... service factor
Radial pin for shaft-hub connection.
Pin shearing stress:
Pressure on shaft:
Pressure on hub:
Shaft torsional stress:
where:
T .... torque [Nmm, lb in]
D .... shaft diameter [mm, in]
D1 ... hub diameter [mm, in]
d .... pin diameter [mm, in]
KSb, KSp ... service factor
Desired safety.
With regards importance of the coupling, quality of production and accuracy of the calculation, it is usually chosen in a range from 1.5 to 3. Orientation values for choice of safety: 1.3 to 1.5 - Very accurate input information, perfect knowledge of material characteristics, high quality and exact following of production technology; insignificant couplings, damage to which does not cause any serious consequences. 1.5 to 1.8 - Less accurate calculation without any experimental verification, lower accuracy in production technology, couplings of lower importance. 1.8 to 2.5 - Decreased accuracy of calculations, approximate determination of material characteristics, inaccurate knowledge of actual effects of external loading; large diameters of shafts, very important couplings, damage to which could jeopardize human life or bring about high material losses.
Design of standardized pins
Introduction
The oldest mechanical fastener is undoubtedly the pin A pin is a machine element or fastening component or device that secures the positions of two or more parts relative to one another in a structure or assembly by passing through holes in those parts. Pins usually remain fixed in place by
the friction caused by interference between the pin’s surface and the material surrounding it in the part(s) into which it is inserted.
This friction force is the result of the microscopic asperities on the surface of the pin (whatever material it is made of) and on the surface of the hole surrounding the pin (whatever material those parts are made of)
Any squeezing force from the material into which the pin is installed causes the friction force to be higher. A squeezing force results from the material surrounding the pin pushing back on the pin in
its attempt to recover the elastic portion of the deformation forced upon it by insertion of the pin. However, there are also pins that must be held in place axially to allow intentional radial motion (e.g., rotation of one part relative to another or, at least, to the pin). Pins often have neither heads nor feet and, consequently, are incapable of developing any clamping force. They are intended to operate in shear by bearing against the material into which they are inserted.
As a group, pins are cost effective because of their simplicity of design, ease of installation, and ease of removal for intentional disassembly.
Pins come in many types
1-Straight cylindrical pins are headless cylinders, with or without chamfered ends, used for transmitting torque in round shafts.
2- Dowel pins are often hardened headless cylinders used in machine and tooling fabrications for fixing the position of parts of the machine or parts inserted into the tooling (including jigs and fixtures).
3- Tapered pins are headless tapered rounds used in drilled and/or reamed (often taper-reamed) holes for fixing position or transmitting torque. The taper helps ensure that interference is established through a wedging action.
4- Clevis pins require the use of a second, smaller pin (often a cotter pin) placed Bthrough a hole drilled diametrically through the body of the headless end of the clevis pin in order to keep it from accidentally withdrawing.
5- Cotter pins are headed pins held in place by bending outward the projecting portions or prongs of a split body at the headless end, thereby preventing un wanted with drawal.
6- Spring pins are held in place by the elastic spring action of the body created by an axial slot or a spiral-wound design. Slotted tubular pins and spirally coiled pins are the two predominant types.
7- Grooved pins typically have three equally spaced, parallel axial grooves impressed longitudinally onto the exterior of the pin body. These grooves ensure positive radial locking in a hole by forcing some of the material of the part into the grooves by plastic deformation.
8- Knurled pins have a cross-textured (‘‘knurled’’) surface for use in soft metal die castings or polymers to prevent unwanted withdrawal.
9- Quick-release pins are used for temporarily fixing the position of parts during assembly or to facilitate disassembly. These pins often use spring-loaded lock-balls located in the pin body in the region that projects through the part being fastened.
10 - Barbed pins are usually headed types with projections along the pin body to facilitate locking in soft materials such as plastics or wood.
They are fabricated from many materials, depending on the design type and intended use. Most, however, are fabricated from various cold-drawn low or medium carbon or low alloy steels and, as mentioned, some are hardened for wear resistance. Other materials typically used include various stainless steels (especially 400-series grades), brasses, bronzes, and beryllium–copper. Special light-duty pins for use with plastics, ceramics, or glasses can be fabricated from other, softer materials
Theory - Fundamentals.
Connecting pins serve to make strong, detachable connections between two mechanical parts, to secure their positions accurately, and to eliminate transversal shifting forces. As a rule, standardized pins manufactured in a wide range of dimensions and designs are used. Pre-stress in the connection between parts is achieved either by means of pin allowance against the hole or the use of conical pins. Conical pins are self-locking and have taper ratio 1: 50. Cylindrical pins are produced as either plain or grooved. Holes for fitted cylindrical pins are drilled or reamed; the common fitting methods are H7/n6, H7/m6, H7/p6.
Grooved pins do not require precise hole fitting and are more resistant to release. On the other hand, they are not suitable for connections that are dismantled frequently, or for connecting aluminium parts. The loading capacity of connections with grooved pins is approximately 20-30% lower. The H11/h11, H12/h11 fitting methods are most frequently used.
Conical pins provide highly accurate and strong connections. They guarantee that the precise position of the parts being connected is maintained even after repeated connection disassembly. They are not suitable for connections subject to vibration and shocks. Holes for conical pins must be reamed in both parts simultaneously; the common fitting methods are H11/h10, H12/h11.
Clevis pins are used for detachable, rotating connections of mechanical parts. As a rule, these connections transfer only transversal forces acting perpendicularly on the clevis pin axis. Clevis pins are generally fitted with a clearance to form coupled connections (rod-clevis couplings). Clevis pins can also be used for short axles of pulleys, travel wheels, etc. The H11/h11, H10/h8, H8/f8, H8/h8, D11/h11, D9/h8 fitting methods are most frequently used. Connecting clevis pins should be secured against axial movement by means of cotter pins, flexible safety rings, nuts, adjusting rings, etc. Standardized clevis pins are produced in versions with or without heads, in which case they are provided with holes for cotter pins.
Pinned couplings are sized, under simplified assumptions, without allowing for the pressing effect and with reasonably reduced allowable stress. Connected parts are checked for deformation of contact surfaces on the hole face. Pins and clevis pins, depending on the connection type, are checked for shearing or bending stresses. As a rule, an additional check for shaft torsional stress is done in torque-loaded shaft-hub connections.
CALCULATIONS
Securing pin.
Pin shearing stress:
Pressure on bottom board:
Pressure on top board:
where:
F .... acting force [N, lb]
s1 ... thickness of bottom board [mm, in]
s2 ... thickness of top board [mm, in]
d .... pin diameter [mm, in]
i ..... number of pins
KL ... load distribution factor
KSb, KSp ... service factor
Pins come in many types
1-Straight cylindrical pins are headless cylinders, with or without chamfered ends, used for transmitting torque in round shafts.
4- Clevis pins require the use of a second, smaller pin (often a cotter pin) placed Bthrough a hole drilled diametrically through the body of the headless end of the clevis pin in order to keep it from accidentally withdrawing.
8- Knurled pins have a cross-textured (‘‘knurled’’) surface for use in soft metal die castings or polymers to prevent unwanted withdrawal.
10 - Barbed pins are usually headed types with projections along the pin body to facilitate locking in soft materials such as plastics or wood.
They are fabricated from many materials, depending on the design type and intended use. Most, however, are fabricated from various cold-drawn low or medium carbon or low alloy steels and, as mentioned, some are hardened for wear resistance. Other materials typically used include various stainless steels (especially 400-series grades), brasses, bronzes, and beryllium–copper. Special light-duty pins for use with plastics, ceramics, or glasses can be fabricated from other, softer materials
Theory - Fundamentals.
Connecting pins serve to make strong, detachable connections between two mechanical parts, to secure their positions accurately, and to eliminate transversal shifting forces. As a rule, standardized pins manufactured in a wide range of dimensions and designs are used. Pre-stress in the connection between parts is achieved either by means of pin allowance against the hole or the use of conical pins. Conical pins are self-locking and have taper ratio 1: 50. Cylindrical pins are produced as either plain or grooved. Holes for fitted cylindrical pins are drilled or reamed; the common fitting methods are H7/n6, H7/m6, H7/p6.
Grooved pins do not require precise hole fitting and are more resistant to release. On the other hand, they are not suitable for connections that are dismantled frequently, or for connecting aluminium parts. The loading capacity of connections with grooved pins is approximately 20-30% lower. The H11/h11, H12/h11 fitting methods are most frequently used.
Conical pins provide highly accurate and strong connections. They guarantee that the precise position of the parts being connected is maintained even after repeated connection disassembly. They are not suitable for connections subject to vibration and shocks. Holes for conical pins must be reamed in both parts simultaneously; the common fitting methods are H11/h10, H12/h11.
Pinned couplings are sized, under simplified assumptions, without allowing for the pressing effect and with reasonably reduced allowable stress. Connected parts are checked for deformation of contact surfaces on the hole face. Pins and clevis pins, depending on the connection type, are checked for shearing or bending stresses. As a rule, an additional check for shaft torsional stress is done in torque-loaded shaft-hub connections.
CALCULATIONS
Securing pin.
Pressure on bottom board:
F .... acting force [N, lb]
s1 ... thickness of bottom board [mm, in]
s2 ... thickness of top board [mm, in]
d .... pin diameter [mm, in]
i ..... number of pins
KL ... load distribution factor
KSb, KSp ... service factor
Cross pin in rod and sleeve.
where:
F .... acting force [N, lb]
D .... rod diameter [mm, in]
D1 ... sleeve diameter [mm, in]
d .... pin diameter [mm, in]
i ..... number of pins
KL ... load distribution factor
KSb, KSp ... service factor
Radial pin for shaft-hub connection.
T .... torque [Nmm, lb in]
D .... shaft diameter [mm, in]
D1 ... hub diameter [mm, in]
d .... pin diameter [mm, in]
KSb, KSp ... service factor
Desired safety.
With regards importance of the coupling, quality of production and accuracy of the calculation, it is usually chosen in a range from 1.5 to 3. Orientation values for choice of safety: 1.3 to 1.5 - Very accurate input information, perfect knowledge of material characteristics, high quality and exact following of production technology; insignificant couplings, damage to which does not cause any serious consequences. 1.5 to 1.8 - Less accurate calculation without any experimental verification, lower accuracy in production technology, couplings of lower importance. 1.8 to 2.5 - Decreased accuracy of calculations, approximate determination of material characteristics, inaccurate knowledge of actual effects of external loading; large diameters of shafts, very important couplings, damage to which could jeopardize human life or bring about high material losses.
Design of standardized pins
thanks for your visit