Re: [CR]The virtues of grinding compound. Shade tree bicycle mechanic how-tos.

(Example: Framebuilders:Mario Confente)

Date: Sat, 10 Sep 2005 10:11:05 -0700 (PDT)
From: "dave martinez" <>
Subject: Re: [CR]The virtues of grinding compound. Shade tree bicycle mechanic how-tos.
In-Reply-To: <>
cc: CR List <>

Hello Harvey,

Your experience reminded me of a bit of good ol' Yankee ingenuity that helped me make a pair of crankarms match a cottered spindle.

I preassembling a 1952 Cinelli Mod B before I was to hand it over to Brian for restoration ("Hello, Brian"??). I just received a really cool FB crankset that was to fit it on a Campagnolo cottered bottom bracket. Both components allegedly had Italian dimensions. When I tried fitting the crankarm on the cottered spindle, it would go in afew millimeters and bind. Ah, those Italian tolerances, "close but no cigar" All I needed was afew silly millimeters.

What to do? I considered a tiny hone, but they proved to be very expensive. I considered asking my friend who helped me with a similar problem years ago, by having HIS friend hone crankarm holes in his custom golf club shop. I hate to use friendships that way. Then, I considered a piece of 12" vinyl hose that's about 1/2" diameter with wet/dry sand paper taped to the center of the hose. I slid the crankarm to the center of the hose to snugly fit in the sandpaper and began rapidly twirling the crankarm. Momentum built up quickly with the steel crankarms. "Hey" this is kinda fun, with my wife at work and the kids in school, I plopped in a Fausto Coppi tape and twirled away, checking my progress from time to time. Soon, one crankarm met tolerance with a perfect fit. The process was repeated.

That experience really makes me appreciate the guys that operated bike shops before cotterless cranks became the norm. Shops back then really earned their keep.

Regards, Dave Martinez Fremont Ca 3rd generation Yankee

Harvey M Sachs <> wrote: Last summer, good buddy Sam FitzSimmons, who seems to able to find anything, told me he found a 10-tooth, inch-pitch cog that I really wanted to get an old-man's reasonable gear on my '38 Paramount (which has a beautiful 26 front that I didn't want to replace).

It arrived. Beautiful! In fact, it was NOS, as far as I could tell. There was only one problem: it wouldn't thread on to any hub I tried. Turned out there was a reason that it survived maybe 50 years NOS: no one could screw it onto a hub. Or even a BB cup (same threading). The the inside diameter of the treading was just too small. Well, there was an old, dull, BB chasing tap lying around, and some valve grinding compound, so I mixed one part of each, and one part elbow grease, and a couple of hours and a beer later the steel cog fits comfortably on the aluminum Paramount hub. I suspect the tap is even duller now, but life happens...

Now, please, I'm not blaming Sam, in any sense at all. I never would have suspected undersize threading, and wouldn't have checked for it before selling an NOS cog. I'm really happy that Sam found it, and sold it to me for a most reasonable price. It's just that these old bikes and their parts do yield the occasional interesting opportunity to try something new. And a decent yarn to share with fellow "addicts."

Thanks also to the list member whose post a month or so ago reminded me of the semi-constructive uses of grinding compound.

harvey sachs
mcLean va