Power at Work: What you should know about bolts, metric and imperial

Some tips to help you through the maze of different grades and nomenclatures of bolts in use around farm machinery


Most of us buy bolts by size, but now that we have both the old imperial system and the more recent metric system, we can easily be confused. When we add the two grading systems for bolts, we become really confounded.

Bolt sizes. The old imperial system sizing was straightforward. We start with a nominal thread diameter of 1/4 inch and go up in 1/16 inch increments until we hit 3/4 inch diameter. These bolts can be obtained in a variety of lengths, usually in 1/4 inch increments from less than one inch to special order long bolts.

Better Farming - December 2008