Metric Bolts: A Variety of Options

Do your eyes glaze over at all the metric bolt choices? We know it can be kind of confusing, especially if you’re not used to ordering metric parts. Let’s look at the meaning of some common terms in the world of “bolt-ology.”

Bolts have different heads that identify their use for different applications. Hex bolts, for instance are simply bolts that have a hexagonal, or six-sided shape to their head. These bolts may have threads extending either halfway or all the way down the shaft and generally require nuts and washers to hold themselves in place. Flange bolts are instantly identifiable by a flat flange that somewhat resembles a washer peeking out from underneath the head but is actually part of the head itself. The flange grips onto the substrate and distributes the clamping force across it just as a washer would, saving you the need for that separate part.

metric flange bolts metric hex bolts








How do we assign measurements to metric bolts? The bolts in our catalog are all identified by the letter M (for “metric”) followed by a pair of numbers. The number immediately following the “M” indicates the diameter of the bolt in millimeters, and the next number (usually expressed in decimal notation) indicates the “pitch” or length of the threads, also in millimeters. You’ll also see an abbreviation at the end of the description line that indicates the material used, such as SS for stainless steel and/or A-2 for steel in general. Or sometimes we’ll just write it out as Brass, Nylon, etc.

If you feel less than 100 percent certain about which metric bolts or other fasteners to order through our online store, save yourself some potential buyer’s remorse and contact us with any questions you may have. We can help you make the right choice, every time.

About the author

Mr. Metric is the spokesperson for, an online store for metric fasteners. Get $7.50 flat shipping with no minimum orders, plus advice and best practices for using metric fasteners in any application.

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