shapes of pins
Shapes of pins:
- Cotter Pins
- Clevis Pins
- Taper Pins
- Roll Pins
- Dowel Pins
- Groove Pins
- Knurled Pins
A cotter pin (also known as a cotter key) is a metal fastener with two tines that are bent during installation, similar to a staple or rivet. Typically made of wire with a half-circular cross section, cotter pins come in multiple sizes and types. In the UK the term split pin has traditionally been used, the term cotter being reserved for the round cotter that was used to fix bicycle pedal cranks to their shaft.
A new cotter pin (see figure, A) will have its flat inner surfaces touching for most of its length, so that it appears to be a split cylinder (figure, D). Once inserted, the two ends of the pin are bent apart, locking it in place (figure, B). In order to facilitate the initial separation of the tines, one tine of the cotter pin is often noticeably longer than the other; and in order to ease insertion into a hole, the longer tine is often slightly curved or beveled to overlap the tip of the shorter tine.
Cotter pins are frequently used to secure other fasteners, e.g. clevis pins, as well as being used in combination with hardboard discs as a traditional jointing technique for teddy bears. A castellated nut is castellated so that a split pin can be used to keep it from coming loose.
Cotter pins are typically made of very soft metal, making them easy to install and remove, but also making it inadvisable to use them to resist strong shear forces. It is advisable to always replace the cotter pin rather than to reuse it, lest metal fatigue cause it to fail in use.
Spring-type cotter pins, sometimes known as R-pins from their shape, are also available, which are not designed to be permanently bent. In this design, only one section of the pin passes through the shaft to be secured, the other section being curved to wrap around the outside of the shaft (figure, C). This type of pin is usually made of round wire of a harder metal than is appropriate for traditional cotter pins.
A clevis pin is a type of fastener that will allow rotation of the connected parts about the axis of the pin. A clevis pin consists of a head, shank and hole. The hole passes through the shank at the opposite end of the pin from the head. A cotter pin is inserted through the hole to keep the clevis pin in place after assembly of the parts to be fastened.
Commonly the clevis pin is used with a shackle. A straight shackle looks like the letter C, with holes at each end; when you insert the clevis pin you create a D with the clevis able to rotate about the axis of the pin. A twist shackle provides a loop at a right angle to the axis of rotation.
A large bolt can function as a clevis pin, but a bolt is not intended to take the lateral stress that a clevis pin must handle. The heads of clevis pins sold to the farm trade or for other types of rigging are typically larger and safer to use.
Older implements, intended to be pulled by a team of draft animals, require a twist shackle to be hitched.
Like a set screw, a clevis pin is often used to prevent two other pieces from moving relative to each other. A clevis pin is less adjustable, in that it can hold the two parts in exactly one relative position (because holes must be drilled in both parts). A clevis pin is also more secure, as it is less apt to come loose due to vibration.
Hardened and precisely shaped dowel pins are used to keep machine components in accurate alignment; they are also used as location guides for adjacent machine parts and to keep the two sections of a punch and die in alignment.
A Taper pin is a fastener used in mechanical engineering. They are steel rods with one end having a slightly larger diameter than the other. Standard inch sized taper pins have a taper on diameter of 1:48 while metric ones have a taper of 1:50. A 1:48 taper means that one end of a 4 foot long bar (48 inches) will be 1 inch smaller in diameter than the other end. In smaller dimensions this is a 1/4 inch taper over a 1 foot length.
A Groove Pin is a solid cylindrical pin with three longitudinal grooves, manufactured from bar or coil stock. The three grooves are pressed into the cylindrical body to expand its diameter to a size greater than its nominal diameter in a precisely controlled way. Material is displaced, but not removed, from the pin the process.
Groove Pin Advantages
- They withstand severe shock and vibration.
- They are solid.
- They are available in different groove types to suit a wider range of applications.
- They require only a straight-drilled hole.
- They reduce the number of steps in your assembly operation.
- They may be driven with a hammer, air cylinder or hydraulic press.
- They may be hopper-fed for automatic installation.
- They allow easy installation and quick assembly.
- They can be removed and reused.
They are similar to grooved pins because they have serration around the nominal diameter of the pin. The knurled pin differs from the grooved pin while there are many serrations on a knurled pin. Also, knurled pins are typically roll formed whereas grooved pins are swaged. A knurled section may have either a straight knurl, a helical knurl, or a diamond knurl configuration. Knurled pins are available with nominal diameters from 3/32" through 3/8" and lengths from 3/16" through 3
The serrations on a knurled pin, when compressed by insertion into a hole, result in forces, which hold the fastener in place. Radial forces are more evenly distributed around the diameter of a hole for knurled pins than for grooved pins. This is because a knurled pin has more points of contact with a hole than a grooved pin. The teeth may broach the mating hole when the material is softer and more ductile than the pin material.
The amount of expansion is predicated on the knurl pitch. Coarse knurls provide greater expansion than fine knurls. A knurled pin should have a minimum of 15 teeth to allow proper feed and rolling capability. The number of teeth must be a whole number to allow for proper tracking and avoid slivering. The capability on expanded diameter tolerance is +/-.002.
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