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Crown resizing

Old 04-11-22, 09:33 AM
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Rage
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Crown resizing

So, I left one of my bikes at my old workplace where I am on-site every few weeks on a consulting basis. Because of the pandemic, the building and bike room has been pretty much empty since the beginning of lockdown.

Anyway, I go in the other day and find someone has lifted the bars, stem, headset, fork and the wheels off my bike.
Dagnabbit! Lots of expletives. But I guess I shouldn’t have just left it there for months at a stretch.

I bring what’s left home and assemble the parts I need to put her back together out of my trusty old parts bin.
Aha! Luckily, I have everything I need to do so!
Except my headset’s crown race is 26.4 and the crown on the fork to go on there is 27.0.

Anybody have a DIY way to resize the crown on the fork steerer tube or do I gotta bring it in to a shop with the appropriate tools?
Thanks in advance!
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Old 04-11-22, 09:46 AM
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To be perfectly clear, I need to get a 26.4 crown race onto a fork steerer tube with a crown of 27.0.
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Old 04-11-22, 11:16 AM
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That was clear enough. The correct way to fit a 26.4 crown race on a 27.0 fork is to have the fork steerer base milled down with the proper tools. Most good bike shops can do that at modest cost. Years ago I had my LBS mill the 27.0 fork on my '85 Bridgestown down to 26.4 and it worked perfectly.

This is not a DIY project with a hand file as keeping the crown race centered is essential. Alternatively, buy a 27.0 crown race for your headset.

Last edited by HillRider; 04-11-22 at 11:19 AM.
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Old 04-11-22, 11:41 AM
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Thanks, HIllrider.
I was just hoping to be able to knock it out myself without having to head to the shop.
And it would have been sweet/serendipitous if all the parts I had laying around worked out.
But I was pretty sure I’d have to bring it in. It was just a Hail Mary before I broke down.
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Old 04-11-22, 12:10 PM
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Depending on headset you can buy a crown race separately. I know many of the Tange you can.
Probably cheaper than having the fork milled.

https://www.benscycle.com/tange-seik...hoCOnQQAvD_BwE
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Old 04-11-22, 05:13 PM
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Thank you, dedhed. That may be the way to go. I have a Tange levin that I think/hope will work as you suggest.
And “milled” was the word I was looking for in my first two posts of this thread. Thank you twice!
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Old 04-11-22, 05:46 PM
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why not just get a 27mm head set ($24) https://www.universalcycles.com/shop...xoCzzEQAvD_BwE

bit of work to remove old and install, but less hassle (imho) than trying to mill down to 26.4
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Old 04-11-22, 06:33 PM
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Also a way to go. And inexpensive, too. Thank you, squirtdad.
Originally, I was hoping to put together some sort of DIY device and knock it out in a day or two.
But looks like it’s gonna take just a little longer. Oh well, what’re you gonna do, am I right?
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Old 04-11-22, 07:44 PM
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Originally Posted by Rage View Post
Thank you, dedhed. That may be the way to go. I have a Tange levin that I think/hope will work as you suggest.
And “milled” was the word I was looking for in my first two posts of this thread. Thank you twice!
​​​​​​https://www.retro-gression.com/produ...31927412621373
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Old 04-12-22, 07:14 PM
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For information, even though there are some great suggestions above that are less involved ( and this is not typically what DIY would refer to ), this is a perfect job for turning ( as opposed to milling ) on a lathe.

Last edited by redshift1; 04-12-22 at 07:28 PM. Reason: Add info.
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Old 04-12-22, 08:05 PM
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Originally Posted by redshift1 View Post
For information, even though there are some great suggestions above that are less involved ( and this is not typically what DIY would refer to ), this is a perfect job for turning ( as opposed to milling ) on a lathe.
A Good LBS will have the proper tool to do this quickly and easily.

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Old 04-13-22, 12:21 PM
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Originally Posted by redshift1 View Post
For information, even though there are some great suggestions above that are less involved ( and this is not typically what DIY would refer to ), this is a perfect job for turning ( as opposed to milling ) on a lathe.

Easier said then done and best done before the blades are attached. A lathe with a spindle bore large enough to fit a steerer in it (to lessen the free/extended from the chuck amount of the fork) isn't the usual home/hobby lathe. So for most people that means finding a machine shop willing to do a small one off job. It seems to me that finding a LBS with a crown race seat milling tool might be about the same effort for the OP and also start to establish a relationship with said shop that will come in handy many more times over the years. Andy
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Old 04-13-22, 01:28 PM
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Thanks for the responses, you guys. Greatly appreciated.

Further complicating things, I just got a new fork that may be better suited as a replacement. Found a cheap decent wheel set and got this fork as part of the deal.
Same rake as the original. The replacement fork was just slightly off. I guess that one might just be straying in the parts bin.
New fork is threadless, though, so I gotta get a new headset. So, however I proceed it’s going to take longer and be more involved than I thought originally.
Just when the weather’s getting nice enough to be outdoors, too.
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Old 04-15-22, 10:18 AM
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Originally Posted by Andrew R Stewart View Post
Easier said then done and best done before the blades are attached. A lathe with a spindle bore large enough to fit a steerer in it (to lessen the free/extended from the chuck amount of the fork) isn't the usual home/hobby lathe. So for most people that means finding a machine shop willing to do a small one off job. It seems to me that finding a LBS with a crown race seat milling tool might be about the same effort for the OP and also start to establish a relationship with said shop that will come in handy many more times over the years. Andy
At the small framebuilding shop where I worked, milling the fork crown on the lathe was the last step, done even AFTER powder coating. Blades are welded to the steerer tube, then the crown race is brazed in place. This necessitates the need to mill the race concentric and perpendicular to the steerer tube AFTER welding and brazing, as there is no guarantee the tube and crown race won't be perfectly aligned. And why do it before paint/powder coat when it will only foul the crown race surface? Thus milling was done as "final prep" to facilitate proper crown race installation. Good for the IBD to not have to worry about milling it.

And yes, this would be a VERY expensive "one-off" job for a machine shop. I would assume $300 or more in many urban areas. Remember, doing one job means missing the opportunity of another. And if the other jobs would bring in $300 bucks, you charge that amount, regardless of "how easy or quick" the fork milling job would be.

A dude posting on CL was selling a bike and mentioned how pissed he was when the boutique manufacturer of the frame was going to charge an "exorbitant" amount for some "simple" job. I had to explain to him that his "simple" job would take the frame builder away from more lucrative and worthwhile work, so thus the high cost. Opportunity cost lost has to be recouped.

And this is why fork crowns are milled with a hand tool at the LBS for $30 instead of in a machine shop for $300!
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