We’ve posted about Bolt Depots’ online fastener guides and templates before, but they’re just too valuable of a resource not to mention again. These free online and downloadable references contain pretty much everything you need to know about common nuts, bolts, screws, washers, and related hardware. The documents also cover more exotic fastener types like J-bolts, sex bolts, shoulder bolts, and more.

The 28-page guide covers the anatomy of bolts and screws, different head types, drive types, thread count and pitch, and how to measure diameter and length. The majority of the document is full-size “lay-over” reproductions of common (and not so common) fasteners so that you can size the bolts you have by eye-balling them on over the guide. Being more of a visual than a numbers person, I find these lay-over guides extremely helpful. Every page of the guidebook also has a scale accuracy ruler so that you can check to make sure that you properly printed the page for accurate bolt identification.

Going through these guides, you learn lots of useful things like:

  • When measuring screws, you measure from the base of a panhead screw to the end. On a flathead screw, you measure from the top of the screw to the end. On an oval-head screw, you measure from the part that will end up below the surface of the workpiece. Basically, the rule is to measure the length of the screw that will end up below the surface of the work.
  • Washers are measured by their inner diameter which is the diameter of the bolt that they match, so an 8mm washer matches an 8mm bolt.
  • Different washer patterns have different outside diameters. For example, hardened US washers are available in USS (wider) and SAE (narrower) patterns. Fender washers have large outside diameters.
  • Fastener Grade (US) or Class (metric) refers to the mechanical properties of the fastener material. Generally, a higher number indicates a stronger, more hardened (but also more brittle) fastener.

You can access all of the guides on Bolt Depot’s Fastener Information page.

[Thanks to Meredith Scheff-King for the reminder.]