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Pins should be harder than the component parts which they join. Pins which are not supposed to wear should be hardened.
- Cylindrical pins
Cylindrical pins are made of bright-drawn constructional steel having tensile strength of approximately 500 MPa.
Cylindrical pins which are not hardened will be deformed permanently and cannot be used again.
There are different types of cylindrical pins. Some are hardened, some are not. There are two grades of unhardened pins with different tolerance zones, viz. m 6 and k 9. Outwardly you can know them by the shapes of their heads. A close fit of pins can be achieved by reaming the bore hole.
Sample designation: Cylindrical pin Æ 6 m 6 × 20
- Nominal diameter 6 mm
- Tolerance zone m 6
- Pin length 20 mm
Figure 2 Cylindrical pins
1 with ISA tolerance zone m 6, 2 with ISA tolerance zone h 9, 3 with ISA tolerance zone m 6-hardened
- Taper pins
Taper pins are generally made of mild steel having tensile strength of approximately 500 MPa. Taper pins can be used several times. Their taper per unit length is mostly 1: 50. Most taper pins are inserted into tapered holes to provide safe and firm pinning. The tapered hole (which has a taper per unit length of 1:50) is produced with a taper reamer. The nominal diameter of a taper pin is measured at its narrow end. Some taper pins have external or internal threads at their opposite end.
Sample designation: Taper pin Æ 6 × 20
- Nominal diameter 6 mm (at thin end)
- Taper pin length 20 mm
Figure 3 Tapered pins (1: 50)
1 standard design, 2 pin with internal thread
- Grooved pins
Grooved pins are made of blank-drawn steel having tensile strength of 600 to 700 MPa. Grooved pins have three grooves arranged lengthwise at distances of 120 degrees along the circumference. Different types of grooved pins are known by the shape of their grooves.
Grooved pins are driven into simple, unreamed bore holes. A tight fit is obtained by the deformation of the edges along the grooves. Grooved pins can be used as many as 20 times.
Figure 4 Grooved pins
1 cylindrical grooved pin, 2 grooved taper pin, 3 close-tolerance grooved pin, 4 center-grooved dowel pin, 5 half length reserve taper grooved dowel pin
- Grooved drive studs
Grooved drive studs are a special variety of grooved pins. They are made of steel having tensile strength of about 400 MPa, or of copper, brass or light metal. Grooved drive studs are identified by the shape of their heads.
Sample designations: Grooved drive stud, round head Æ 4 × 20
- Nominal diameter 4 mm
- Length without the head 20 mm
Grooved drive stud, countersunk Æ 4 × 20
- Nominal diameter 4 mm
- Length with the head 20 mm
Figure 5 Grooved drive studs
1 grooved drive stud, round head, 2 grooved drive stud, countersunk
- Dowel pins (taper sleeve)
Dowel pins are made of rolled and hardened spring steel strip. They have very high strength. Oversize dowel pins are driven into simple bore holes where they respond to elastic shocks.
Dowel pins can be used as often as needed.
Figure 6 Dowel pin
Name the main types of pins
used.
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