Does anyone know another source for these stem binders? All of the others I have found are much bigger and/or a lot more $$. I also like that they are pre-slotted. I’m happy to buy them from @BikeFabSupply but it’d be cool if there was another source in the meantime.
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I prefer PMW for those, they’re made of CrMo and yes it does matter, I have seen lots of braze-on pinchbolts that yielded in use. Assuming you’re charging enough for your stems, saving $5 to use an inferior pinchbolt doesn’t seem worth it. Before PMW sold theirs, I made my own from 4130 rod because the cr@p steel ones I could get at the time sometimes yielded in use. Usually just a little, but visibly, to my eye at least. (Customers seldom notice, but counting on that is lame.) When the BO yields, the screw is no longer in a straight line, so there’s a bending load on it. Bending on a threaded fastener subjected to cyclical loads is a recipe for fatigue, and not the mellow kind with lots of warning, the bolt will snap completely when the crack length is still too small to see or feel, no warning.
The BFS ones could be alloy steel too but I doubt it, they’d say so, right? So it’s a good bet they are plain low-carbon steel.
The fact that the BFS ones are pre-mitered does me no good since I’d have to miter them anyway, the supplied miter isn’t deep enough. Maximizing depth of the miter is important to the strength and reliability of the clamp. Shallow miter also increases the bending load on the BO and on the screw inside it.
BFS BOs come with a stainless screw, which you should throw away. Unless it’s a very fancy SS SHCS, most of those have a yield strength of 60 or 70 ksi, about half the strength of a good class 10.9, and less than half the strength of a class 12.9
I personally know of 4 people who had a handlebar pinchbolt break. All were on fancy custom stems from USA boutique framebuilders. All had installed cheap hardware-store-grade M6 SS. One was not riding, the bike fell over. Two were able to ride it to a stop without crashing, one crashed with broken collarbone. Mass-produced (cheap) stems that use M6 screws seldom have this problem because they use stronger screws. Having your customer crash because you used a cheaper fastener, than say Hissing Lung used on $10 stems in the '90s, is bad for business.
This rant is only about designs with a single bolt, or with two bolt removable-faceplate style where the two bolts are in series not in parallel, so they are not sharing the load, there’s no redundancy. If either bolt breaks you’re looking for a soft place to land. Weak M6 bolts are only acceptable IMHO when they are in parallel, two bolts side-by-side sharing the load (which includes 4-bolt faceplate style).
If you must have stainless, there are high-strength SS SHCS out there, but $$. Here’s an example on McMaster
Yield on those is 120 ksi, nearly 2x the strength of generics. Roughly equivalent to class 10.9.
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I appreciate the response, I’ve been using them mostly for my own stems and do plan to use the paragon binders for customers. When I’m trying out goofy stuff for my own bikes though it’s nice to keep cheaper parts around.
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