Set screws and bolts… What is the difference?

31 January 2023

A set screw has thread running the entire length to the head whereas a bolt is partially thread.

The thread on a bolt is 2x its diameter plus 6mm (up to 125mm)
For example the thread on a 8mm bolt would be 22mm

For larger bolts up to 200mm it is the diameter plus 12mm.
For example 8mm bolt at this length would 28mm

So, what is thread pitch?

Thread pitch, along with threads per inch are ways to describe fasteners to ensure you get the right size you need for the job.

Thread Pitch is the distance from one thread to the next and is used as metric form of measurement.

You can get coarse or fine pitch. Coarse pitch is more generally more common whilst fine pitch allows for greater adjustment accuracy.

Thread pitch, on the screw in the image is 1.75mm, and for an M12 set screw, this would be a coarse pitch. 

Threads per inch is an imperial measurement and is a simple description of how many threads there are in one inch.

In the example, there are 13 threads per inch. So a hex set with a 1/2” thread diameter, 13 threads per inch and a 2” length would be shown as 1/2”-13 x 2” Hex Set Screw

If you are still unsure of the correct fixing or fastener for you contact our sales team on 01482 324731 / sales@frscott.co.uk