How Is Bolt Length Measured

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.

How is bolt length determined?

General. Fastener length is generally measured from the point where the surface of the material will be when the fastener is installed to the end of the fastener.

What does M8 20 mean?

Here’s what the description means… M = Metric thread designation. 8 = Nominal diameter, in millimeters. 1.0 = Pitch (distance from thread to thread), in millimeters. 20 = Length, in millimeters (see below)