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Fork crown race seat squareness

Old 08-14-22, 12:08 AM
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redshift1
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Fork crown race seat squareness

Hi. Does anyone know how I can check if the fork machined surface that the crown race sits on, is square to the fork steerer tube ? Please see arrow in photo. I do not have a lathe.

Thanks.
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Old 08-14-22, 12:33 AM
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Campagnolo and Park made a toll for that
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Old 08-14-22, 01:38 AM
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Thanks. I do have a Cyclus cutting tool for that surface which I have used ( with some light cuts ) but I still would like to perform a check to actually confirm the surface is square to the steerer tube.
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Old 08-14-22, 06:35 AM
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One could secure the fork's steerer onto a Vee block and placing that on a machinist's flat surface use an indicator to sweep the race seat. Do know that if you were to want to cut the seat with a tool the chrome will need to be removed from the to be cut surfaces, or don't expect a shop to offer to do this.

Just as common is the head tube end faces not being square to the axis and bent steerers will create the same "tight yet loose" headset adjustment that results from miss aligned bearing surfaces. Andy
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Old 08-14-22, 07:09 AM
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Have you experienced a problem with this fork or is this just a preemptive worry?
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Old 08-14-22, 07:12 AM
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Originally Posted by redshift1 View Post
Thanks. I do have a Cyclus cutting tool for that surface which I have used ( with some light cuts ) but I still would like to perform a check to actually confirm the surface is square to the steerer tube.
Campagnolo tool #732 should sit squarely on the race seat, with the red line on the tool "up." The tool should not sit on the race seat with the red line "down;" that would indicate that the race seat was cut too small.
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Old 08-14-22, 06:29 PM
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Thanks for the above responses.

That was a good suggestion to use V-blocks and a machinist's table but unfortunately I no longer have access to that equipment ( I was a student at a tech. college ).

And yes, I did remove the chrome plating prior to using the Cyclus tool. For information, I thought this tool was high quality ( the cutter cut very well ) and I think it squared up the seat, but perhaps I did not remove enough metal to complete the procedure.

The problem I think I had, was when I initially fitted the crown race for what I thought was the final assembly, I noticed a little sliver of light between the crown race and the fork seat, in the same spot relative to the fork (I refitted the crown race turning it to a new position several times) when I held the fork up with a light source behind it. This made me think the crown race was not sitting on a square fork seat. As seen in photo.

As the headset was kind of costly ( Edco Competition ), I didn't want to just ignore the issue as I wouldn't think it would last long if the forces in operation were all on a few caged balls instead of being shared equally.

I have no pre-existing knowledge of whether the fork was satisfactory in previous operation as I bought it as a frame and fork ( 1986 Peugeot Aneto ) about 10 years ago and finally have decided to use it for my main ride.

As much as I love Peugeot, I am not so sure this fork was machined perfectly as the chrome plating was present ( before I removed it ) indicating this was how the factory sent it out.

And also, with a quick trial assembly ( after the light fork seat cutting I did ), I am still getting a slight "tight then looser" observation when the fork is rotated in full circles, tighter at the same one point and looser at the same 180-degrees-away point, although I no longer can see the sliver of light under the crown race.


Last edited by redshift1; 08-14-22 at 06:37 PM.
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Old 08-14-22, 06:37 PM
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I would try to hammer down the up lifted part of the crown race with a drift punch or chisel contacting above the bearing track. Then reassemble the headset again and see how it adjusts. When i drive the crown seat down i often spin the tool part of a rotation and resmack it a few times after the "closing clunk:" is heard. If the sliver of light can't be "removed" I might recut the seat ever so slightly and retry the race seating. Have you tried a different headset yet? Andy
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Old 08-14-22, 07:43 PM
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“Did I remove enough” can be resolved by covering the surface to be cut with a thin layer of sharpie or similar marker. Once the marker is gone the entire surface has been cut. The entire cut surface being square to the steer tube is a function of proper use of the cutter.
Without an indicator or known square ended tube there isn’t a great way to check and get a numeric value.

In theory you mount the upper headset then rig a scribe from there to the crown race seat, but that’s full of opportunity for error.

I’m with the above suggestion. Try to drive it home and then see if the headset adjusts properly.
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Old 08-14-22, 10:05 PM
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...I agree that the first thing I would do, presented with the issue you describe and your photo, is to hit it with a bigger hammer.
I am going to repeat some stuff you might already know. prior to setting the race, grease the seat and the interior of the race.

I presuming you have a proper crown race setting tool, some sort of wooden sawhorse or other wood block to support the fork crown from beneath, and a big hammer. This is one of those jobs where the bigger hammer jokes originated.
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Old 08-15-22, 08:28 AM
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Yes I have tried two different headsets and believe me, the problem is not due to the race not seating. I have the proper heavy race driver tool and a large hammer and I set the forks up securely with a wooden support between the fork blades under the crown. Plenty of force applied to the race. ( I also oiled the fitted surfaces.)

Using the marker pen to monitor metal removal is a good idea. I think I have already improved the situation with the crown race seat cutter. Perhaps I will try it a second time.

And it does appear now that there is no easy way to check that seat for squareness.

Just a final question - if a headset was fully assembled and adjusted on a fork with an out of square crown race seat, what would the symptoms be when turning the forks ? Tight then loose as the forks are spun ?
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Old 08-15-22, 09:07 AM
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Originally Posted by redshift1 View Post

Just a final question - if a headset was fully assembled and adjusted on a fork with an out of square crown race seat, what would the symptoms be when turning the forks ? Tight then loose as the forks are spun ?
...yes. If you can find a sealed bearing headset that will work in your application, they are less problematic in this regard. The races for the bearings and the clearances are already set within the sealed cartridge bearings. Unfortunately, they are not always available in the head tube size and stack height you might be dealing with. Be careful with that cutter. It's not hard to remove too much.
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Old 08-16-22, 05:15 AM
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That's a great idea about the possibility of using a sealed cartridge headset. First I will try cutting the seat again but will go gently. Thanks for the information.
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Old 08-18-22, 07:22 AM
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Originally Posted by redshift1 View Post
if a headset was fully assembled and adjusted on a fork with an out of square crown race seat, what would the symptoms be when turning the forks ? Tight then loose as the forks are spun ?
Yes. It will bind in places, and be loose in other places.
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Old 08-18-22, 07:04 PM
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Thanks for the confirmation.
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