Bolt Measuring Guide

ALL YOU NEED TO KNOW ABOUT MEASURING BOLTS

IDEAL BOLT MEASURING TOOLS

For precision measuring we would recommend the use of Digital Vernier Calipers and a Thread Gauge to measure thread pitch. For standard bolts in the range of M5 – M12

MEASURING A FASTENER

Shank Diameter

Also called Major diameter. The diameter of a bolt is the Shank diameter, expressed in millimetres for Metric bolts. Because this is approximately the same as the Major or Thread diameter the thread diameter measurement can be used for fully threaded bolts.

Shank Length

Fastener length is measured from where the material surface is assumed to be, to the end of the fastener. For fasteners where the head usually sits above the surface, the measurement is from directly under the head to the end of the fastener. For fasteners that are designed to be countersunk, the measurement is made from the point on the head where the surface of the material is, to the end of the fastener.

Shank length

Thread Pitch

Metric fasteners are specified with a thread pitch instead of a thread count. The thread pitch is the distance between threads expressed in millimetres (measured along the length of the fastener). For example a thread pitch of 1.5 means that the distance between one thread and the next is 1.5mm. In general smaller fasteners have finer thread so they have lower thread pitch.

Thread Pitch