Casati steel fork interference fit question...

[jimbolina]

I have a brand new Casati steel road fork which I had made for me recently. It has a 1'' threaded steerer and is chromed.

The chroming has of course, enlarged the crown race seat dimension on this fork to 26.53mm diameter. My Sutherland's manual states the Campagnolo Record crown race (inside diameter) is 26.3, and calls for the correct press fit to be 26.4.

My intent is to install a brand new Campy Record (alloy 1'' threaded) headset.

My question is, is the 26.53 too large to properly accept the race, or should I have the seat area turned down a tad? I'd hate to force-press that race component and risk damaging either the race itself (crack) or the actual seat area on my new fork.

Not many folks like to mill chrome plating due to its extreme hardness, so one option is lathe turning, of course. Another is simply hand filing.

Filing seems the most practical, if done carefully. If that's the better option, which file type should I purchase to accomplish this task? And, do I need to only scuff up the chrome or get down to bare metal?

I appreciate any thoughtful assistance...

[rccardr]

Campagnolo crown races are notorious for cracking in that situation, so better to reduce the seat a little bit. A little hand filing should be fine, it's only .065mm you have to remove from the surface.

Not sure whether a crown race reamer would play nice with chrome plating. A 3/4 inch flat file intended to be used on steel should do the trick.

[Peter P.]

I'd sooner sand the I.D. of the fork crown race to 26.4mm than try to reduce the O.D. of the fork crown to 26.4, as it's easier to replace the headset than the fork, and difficult to maintain the consistent O.D. of the fork crown. Yes; you can lathe turn it, but the machinist has to understand what you're trying to achieve. If they're cavalier about things (read: not bicycle knowledgeable) they might blow it.

If you botch filing the fork crown race and lose your press-fit tolerances, you can use Loctitie 680 to secure the crown race to the fork.

Typically, the fork is 26.5mm and the crown race is 26.4, providing the press-fit you want. I find it odd that Campy would spec such a non-standard number. Have you actually measured the crown race you want to use?

[Kontact]

My Sutherland's manual states the Campagnolo Record crown race (inside diameter) is 26.3, and calls for the correct press fit to be 26.4.


Are you sure? Sheldon isn't always right, but 26.4 for the old Campy headset dimension was the race inside diameter, not 26.3.

So I'd measure the race, first.

If you want to reduce the fork OD, I would use sandpaper with a continuous turning motion to avoid high and low spots. It will take a little time, so watch TV while you do it. But if you are careful it will be precise enough.

[jimbolina]

I'd sooner sand the I.D. of the fork crown race to 26.4mm than try to reduce the O.D. of the fork crown to 26.4, as it's easier to replace the headset than the fork, and difficult to maintain the consistent O.D. of the fork crown.

I rather like the idea of reducing the inside diameter of the race than attempting to do so on the fork itself.

You mentioned sanding. Would a small half-round file be better? Sanding sounds like it would take forever on that hard steel crown race.

[rccardr]

It's half of a tenth of a millimeter, so it won't take much to make it fit correctly regardless of which path you take. Assuming your measurements listed above are correct.

Easy way to sand the inside of the crown race is to wind sandpaper around a round columnar shaped object of the approximate correct diameter- e.g. closet pole, toilet paper roll, etc. Look around, you'll find something the right size.

[Kontact]

I would sand the part that is out of spec, instead of sanding every crown race that ever gets mounted on it.

[jimbolina]

Is a good or even ideal interference fit on a component such as this .10mm?

[cnighbor1]

I think this posting is too racey for posting
Yes enlarge lower crown Just wrap wet of dry sandpaper around a 1" wood dowel and start sanding moving contact points around A perfect 0 is not needed Just needs to touch say 50% of fork crown race and it will hold

[e-RICHIE]

I appreciate any thoughtful assistance...

Have you asked Casati what they'd recommend?
I'd like to hear their point of view.

[jimbolina]

Have you asked Casati what they'd recommend?
I'd like to hear their point of view.

Yes - no response.

[e-RICHIE]

Yes - no response.

In how much time since receipt, and then email?

[jimbolina]

In how much time since receipt, and then email?

About six weeks or a tad more...

[e-RICHIE]

About six weeks or a tad more...

Then use a cutter or have it lathe turned.
Somehow you have to make it fit the part.
Or find a part that fits it.

[oldpotatoe]

Then use a cutter or have it lathe turned.
Somehow you have to make it fit the part.
Or find a part that fits it.

I agree..use a good cutter, I've done this more than once on chromed forks. Italian chrome ain't all that tough generally.

[Polyglot]

Have you asked Casati what they'd recommend?
I'd like to hear their point of view.

I agree..use a good cutter, I've done this more than once on chromed forks. Italian chrome ain't all that tough generally.

I believe that Casati realized that they should have prepped it for you and are a bit embarrassed, and thus have not responded. I have a cutter that would clean this up in no time. Generally speaking, once the cutter edges bite into the chrome you are fine. At the edge of the chrome, there usually are minor imperfections that allow you to start the cut without difficulty.

[jimbolina]

[QUOTE=Peter P.

Typically, the fork is 26.5mm and the crown race is 26.4, providing the press-fit you want. I find it odd that Campy would spec such a non-standard number. Have you actually measured the crown race you want to use?[/QUOTE]

Well, like a blithering idiot I neglected to actually measure the component myself (thanks for the reminder!) rather than simply rely solely on the old Sutherland's manual. Indeed, the I.D. of the (new production) Campy crown race is right at 26.4.mm. The Casati fork race seat (including plating) is about 26.54mm. Looks like I don't really have an issue after all, as I think that would fall within the +- range of interference fitment.

I'm pretty good at cooking-up problems that aren't really there I guess.

Thanks for the excellent suggestions and potential fixes guys. Great bunch of problem-solvers here!

[Kontact]

Well, like a blithering idiot I neglected to actually measure the component myself (thanks for the reminder!) rather than simply rely solely on the old Sutherland's manual. Indeed, the I.D. of the (new production) Campy crown race is right at 26.4.mm. The Casati fork race seat (including plating) is about 26.54mm. Looks like I don't really have an issue after all, as I think that would fall within the +- range of interference fitment.

I'm pretty good at cooking-up problems that aren't really there I guess.

Thanks for the excellent suggestions and potential fixes guys. Great bunch of problem-solvers here!

In all the years I worked at bike shops, I've never actually seen a Sutherland's. But whenever things like this come up, Sutherland's never seems to actually help matters. I don't know why Sutherland's says that the crown ID is 26.3, and maybe it never was.

[Peter P.]

Glad you found your solution!

This entire problem did get me to wonder: If chroming increases the O.D. of the fork crown and puts it out of tolerance for fitting a crown race, what's a builder to do? Unless the builder uses a lathe to cut the crown race (some do), they can't cut it undersized, so chroming will bring it up to spec.

I'd guess it's never been a problem because chrome forks have been around for decades, and no one I know makes a crown race cutter that's undersized to allow for post-facing chrome.

[jimbolina]

In all the years I worked at bike shops, I've never actually seen a Sutherland's. But whenever things like this come up, Sutherland's never seems to actually help matters. I don't know why Sutherland's says that the crown ID is 26.3, and maybe it never was.

Yeah, I bought mine back around 1983 and have used it sporadically while educating myself on bicycle reapair and assembly over those initial 10 years or so and probably came to rely on it too much.

It's only with excellent resources such as this forum where I have found better, more rounded advice and solutions.