Bolt head style, drive style, material, size, and grade are all important elements for selecting the correct metric bolt for your fastening application. Do your eyes glaze over at all the metric bolt choices? We know it can be kind of overwhelming and 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.
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.
Full vs. Partial Threads
To understand how these bolts grip differently, it’s important to understand the basic differences in their designs.
Fully Threaded Metric Bolts: These bolts have threads running the full length of the bolt, from the underside of the head to the tip.
Partially Threaded Metric Bolts: Starting at the underside of the head, these bolts have an area that is free of threads. Called the “grip length,” this area is the full thickness of the bolt shank, and will vary in length according to the recommended application of the bolt.
Mr. Metric (a Mountz company) is the leading metric fastener specialist in North America. Well regarded as experts in metric, Mr. Metric is known for hard to find metric items at competitive prices. Get the right metric fastener from Mr. Metric. If you feel less than 100 percent certain about which metric bolts or other fasteners to order through the Mr. Metric online store, save yourself some potential buyer’s remorse and contact Mr. Metric (1-866-501-9504) with any questions you may have. Mr. Metric can help you make the right choice, every time.