A spring pin (also called tension pin or roll pin) is a mechanical fastener that secures the position of two or more parts of a machine relative to each other. Spring pins have a body diameter which is larger than the hole diameter, and a chamfer on either one or both ends to facilitate starting the pin into the hole. The spring action of the pin allows it to compress as it assumes the diameter of the hole. The force exerted by the pin against the hole wall retains it in the hole, therefore a spring pin is considered a self retaining fastener.
Spring pins may be used to retain a shaft as a journal in a plain bearing, as a type of key to fasten one shaft to another, or to precisely fasten flat faces of mating parts together through symmetric hole locations.

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  1. Tony617

    Bought an Aero Precision Upper with an allen head screw that then a roll pin

    I bought an Aero Precision Upper Receiver and it comes with an allen head screw instead of normal roll pin. Do I need to put any thread locker on the allen screw? I have always had to put a roll pin the secure the forward assist this is my first experience with an allen head bolt.
  2. Tony617

    I ordered a gas tube and package said roll pin was included but there was no roll pin

    I ordered a gas tube and it says the roll pin is included but there wasn't in the package. Can I go to the hardware store and buy an appropriate sized buy one? I have a few spare extractor roll pins but they are too large. I have fewer lower parts kits does anyone if roll for the lower kit will...
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