Fascinated with Fasteners and Flanges
FIGURE A
I
’ve always been intrigued by the bolt thread—that rotating ramp or helical ridge responsible for clamping stuff together. Nuts and bolts. I still recall my very first attraction to the wizardry of something mechanical at around age 10. It was a buddy’s old Clinton two-stroke go-kart engine. He made it run, but it had no muffler, so I just stood in amazement watching the piston go up and down through the flaming exhaust port, smelling the premix and diggin’ all the racket. The seed was planted, and by the age of 17, I was pulling car engines and doing valve jobs. My attraction to fasteners emerged after working at a Honda shop for a few months in 1972. The fasteners on a motorcycle are noticeable and prominent, and Hondas always had attractive and nicely-finished nuts and bolts. Fast-forward fifty years and my obsession with nut and bolt form and function is alive and well. Every bike I build gets ‘the treatment.’ So, while form (the look) is cool, function is more important, especially on a vintage competition machine that spends most of its life buzzing away at high RPM. We’ve all been there: a nut or bolt takes the day off, and vanishes. I have been addicted to flange bolts for quite some time and use them for just about everything on race bike builds. (For period-correct restorations, I use the original fasteners.) Flange bolts and nuts are superior to the nut/lock washer/ flat washer stack, and dropping one thing on the floor is better than dropping three things on the floor. And, while working an all-nighter in the paddock on Saturday night,
FIGURE B
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the fewer parts to keep up with, the better. The flange provides a larger area of load distribution which is easier on the contact surfaces. That larger flange surface acts like a brake and keeps the fastener from loosening and spending the rest of its life in the grass outside turn nine. These flanged nuts and bolts are available in several grades and materials from a variety of sources. Here are a few I rely on. FIGURE A, above, left to right: Not flange bolts, but JIS crosshead screws, 5 and 6 millimeter. PSA: These are not Phillips® screws and using a Phillips® point will damage the screw and the driver. Next is my go-to 6 mm case bolt with 8mm hex head. They are superior to a socket head screw because of their wide flange. Socket head screws have smaller diameter heads which can dig in and deform crankcase cover castings. The fourth fastener is an OEM Honda dish-head bolt. The next two are drilled titanium with dished heads. The M6 has an 8 mm head; the M8 has a 10 mm hex head. FIGURE B left to right: standard 6 mm flange nut, aluminum 6 mm flange nylock nut, 6mm flange nut with metal locking device. I use the 8- and 10-mm versions of these metal lock nuts for securing engine mounting bolts. I like this setup (FIGURE C) for wind screens (with the rubber washer against the plexiglass) and number plates: aluminum 5 mm screw with an aluminum fender washer and aluminum lock nut.
FIGURE C
AMERICAN HISTORIC RACING MOTORCYCLE ASSOCIATION
AUGUST 2021
