Spring Pins - Metric - BZP

Spring Pins go by many different names, including spring tension pins, Sellock pins, roll pins and slotted spring pins.

Spring pins are a self-locking fastener that use tension to hold two or more components together. They are essentially a small hollow steel tube without a head but with chamfered or rounded ends. The pin is slightly larger than the hole that it is being introduced to, so that once inserted into place the outside walls of the sprung steel pin exert pressure and hence grip the hole, holding the pin and the components in position.

To insert a spring pin, cover it in a light lubricant and grip the pin with a pair of long-nose pliers. Offer the chamfered end of the pin to the mouth of the hole and gently tap the pin into position with a small hammer.

Metric is the most common thread type in production today. Usually specified as M then a number x another number. This signifies the thread diameter and the length of the fastener.

For example M4 x 30 means that the major thread diameter (the external distance across the outside of the thread) is 4mm and the length is 30mm. Length is usually measured from the underside of the fastener head.

A BZP or bright zinc plated fastener is one which has a thin coating of zinc added during production. This protective coating adds durability by protecting the product against rust or oxidisation.