Crown race 26.6 sanding
07-21-15, 01:55 PM
#26
verktyg
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You mat run into a stack height problem with a Campy NR headset. The top lock nut needs to be threaded all of the way on to the steerer. You may only be able to get 2-3 turns with a Campy lock nut!
Here's an example of what I'm suggesting. The arrow points to the gap in the threads:
verktyg
Chas.
Here's an example of what I'm suggesting. The arrow points to the gap in the threads:
verktyg
Chas.
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Don't believe everything you think! History is written by those who weren't there....
Chas. ;-)
Don't believe everything you think! History is written by those who weren't there....
Chas. ;-)
07-21-15, 02:20 PM
#27
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I think you mean Foredom tool. I have done the same with a Dremel, the poor man's Foredom.
A sanding drum mounted on a drill press worked better, or at least faster.
A sanding drum mounted on a drill press worked better, or at least faster.
Last edited by Grand Bois; 07-21-15 at 02:27 PM.
07-21-15, 05:30 PM
#28
Too many bikes
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I would see if Elton over at Harris could help you out. If he's still there, that guy knows his stuff. Knows vintage bikes and, I would think they would have a crown race seat cutter.
As for other suggestions mentioned here, I personally would be very careful if taking it to a machine shop. While those guys are used to precision work, I might not feel comfortable taking a fork to someone who didn't know bikes and had never done if before. Still, if you specified the exact size you needed for an interference fit, it might be OK. Still, be careful having a thin, hollow steerer tube chucked in a big lathe. 2 cents.
As for other suggestions mentioned here, I personally would be very careful if taking it to a machine shop. While those guys are used to precision work, I might not feel comfortable taking a fork to someone who didn't know bikes and had never done if before. Still, if you specified the exact size you needed for an interference fit, it might be OK. Still, be careful having a thin, hollow steerer tube chucked in a big lathe. 2 cents.
Instead of calling I went to Harris as they have early evening hours today. The tech at the bench said he wouldn't do milling and he though Jon( not sure?) might, but he wouldn't be in until Thursday - more importantly he didn't think they had the proper guides. In a private message someone suggested I might get good service if I call ahead to Belmont or Cambridge Bicycle. And I will definitely try Broadway Bikes if the others fail.
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07-22-15, 04:28 PM
#29
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I've turned down a 27.0 fork crown seat to 26.4 using a lathe, but noticed that a low speed was required to prevent the (thus imbalanced) offset fork ends from applying bending stress to the crown while spinning.
At a low speed, using a fine cutter that won't chatter, a concentric (with the steerer) can be made.
I've seen guys at bike shops go around the seat with a flat file, as miamijim suggested. Craftsmanship skill will determine how accurately this turns out, and of course you won't be correcting any of the flat portion of the crown race seating this way, but reducing the diameter with a sharp file is a cinch.
At a low speed, using a fine cutter that won't chatter, a concentric (with the steerer) can be made.
I've seen guys at bike shops go around the seat with a flat file, as miamijim suggested. Craftsmanship skill will determine how accurately this turns out, and of course you won't be correcting any of the flat portion of the crown race seating this way, but reducing the diameter with a sharp file is a cinch.
07-22-15, 06:53 PM
#30
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Reducing the diameter is a cinch, true. But as you say, keeping the seat perfectly concentric using a hand file would require some real skill. Like master machinist or toolmaker skill, IMO. I consider myself fairly adept with a file, and even have the proper narrow pillar files with which to do it, but I don't think I'd try this. The crown race seat is one of many places on a good bike that needs to be precisely cut.
Just my opinion, o'course.
Just my opinion, o'course.
