Whether you are assembling machinery, renovating a vintage motorcycle, or simply repairing a wobbly chair, one truth remains - the wrong size bolt can throw the whole project off. In the guide below we will break down how to measure a bolt, in plain English steps, complete with a few industry tips that professionals swear by.
How Do You Measure Up
Understanding the Basics
A bolt is more than just length and thickness, there are multiple dimensions you need to know before buying.
Length - How long the bolt is from tip to the start of the head (or to the end, depending on head type).
Diameter - The width of the threaded shaft.
Thread Pitch - The spacing between threads, which is measured differently, depending on system (Metric or Imperial).
Head Size - The size of the bolt head for the correct spanner or socket.
Pro Tip
Where possible, use callipers or a thread gauge for accuracy. Rulers or tape measures can be too wide to get a precise start point.
Length
When measuring bolt length, the head type matters. For countersunk bolts, measure the entire bolt, including the head. For everything Else (Hex, socket, pan heads), measure from the underside of the head to the end of the bolt.
