Originally Posted by scarlson

Also did some work on chainrings!

I used Sprocketeer to do an ANSI 41 tooth profile. This is a perfect match for bicycle chain roller, as confirmed by several websites, in spite of the information on the Sprocketeer website itself. I had these waterjet cut from 0.160 aluminum plate, the closest match for 4mm plate I can get here in the USA.

I thinned the teeth down on the lathe, and cut the tops off the teeth. The teeth are 2mm wide. A 6-speed chain will roll on and off of them by gravity, so I think this is acceptable! Phew.

I beveled each with a file.

Then I hand-filed the mounting ears for a perfect fit on the cranks, which are not perfect by any stretch.


It seems a lot of hand-matching with files was done at the Herse shop. I am finding original things that look "off" in one way or another all the time. I do my best to reproduce with fidelity, but they're real artisanally-made bikes. No two will be alike. These cranks are not quite a 70mm bolt circle. Maybe 70.5? 71? I doubt the bolts are even in a circle, if we want to split hairs.