Ted Ernst wrote:
>
> I've been musing on the regrinding and had a few Q's about the
> process/results.
> How much materiel has to come off before the race is thru its hardness
> depth? Enough to make a problem if ridden?
> Are the cones/races/cups hardened all the way thru?
> Would that make the fork fixed cone easy to split/crack if too tite on
> fork crown/base position.
> If too much materiel is removed does that increase the radius/radii of
> the paired combination and change the position enuf to maybe cause
some
> very close tolerance parts to have contact/friction?
Ted, yes those questions are haunting me too. I had one lower headset cup/cone bearing re-ground, and I think the bike it's on will be a rider, so I'll be able to report back after some miles. Unfortunately it will take me a while to get it built up, and then it won't be my highest-mileage bike so it will take a while to get real miles on it. Probably a year before I can report back meaningfully -- at least I hope so!! Maybe it'll die inside of 10 miles?! I don't expect it to though. I have a feeling (based on zero evidence) that Campy headsets are fairly tough throughout.
The clearances may have tightened up on my headset between the crown race and the frame, but it still clears, and a miss is as good as a mile, yeah? And less room for splash off the tire to get into the bearing. Since the grinding just went to the bottoms of the deepest dimples and a tiny bit more, and the bottoms of the dimples is where the bearings were sitting already before grinding, I don't think the grinding reduced the clearances much beyond what the dimpling (wear) did. And I've never heard of a headset begin to rub on itself from the wear from riding -- you?
Oh and another point about the balls being at the bottoms of the dimples -- if that was enough to go through the case-hardening depth, then we still haven't harmed it any by re-grinding, we've just taken the rest of the race down to where the balls were sitting anyway. I hope Campy hardens their ball races to a depth deep enough that you can't wear all the way through it in normal use -- but maybe that's just wishful thinking.
I don't know how this guy chooses (or maintains) a profile to grind the curve into the races, but he did ask me what size balls it uses (in this case 1/8"). And though I'm no expert, it sure looks like a race for a 1/8" ball now that it's done -- I don't think he changed the radius much, or not enough to tell by eye anyway.
This particular crown race on my bike is so damn beefy that there's no way the grinding could cause it to split. I've seen more than one Super Record crown race split on a tight-fitting crown, _without_ any re-grinding, so removing any metal off one 'o those might well be risky.
Mark Bulgier
Seattle, WA USA