Bicycle Mechanics - steer tube cutter

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toytech
09-05-10, 08:18 PM
any one still make the tool for sizing a steer tube down from 27mm to 26.4? I could not find one, but maybe I am using the wrong search terms. I have a Var facing tool for the steer tube race, so if a cutter that fit that tool were available...
Bezalel
09-05-10, 08:56 PM
That's alot of material to be removed. I don't think such a tool exists and if it did I'm not sure how safe the results would be.
toytech
09-05-10, 09:01 PM
.6 of a mm is not a lot of material to remove from just the area where the crown race presses on. I am pretty sure my LBS has one, but I would like to have my own if it is ~100.00 mark
fietsbob
09-06-10, 01:04 AM
Ah , Crown Race cutter , I suppose that is what you are asking about..
HillRider
09-06-10, 06:44 AM
Yes, they are certainly made. My LBS has one and years ago milled the crown race seat of my '85 Bridgestone 400 from JIS to ISO diameter. Here is a source for various models:
http://www.biketoolsetc.com/index.cgi?id=910360224408&c=Tools&sc=Fork&tc=Crown-Race-Cutter-Sets
These things are quite expensive so unless you are doing a lot of older JIS bikes, it's probably not worth owning one.
That would be about 0.01" of material.
JohnDThompson
09-06-10, 09:07 AM
That's alot of material to be removed. I don't think such a tool exists and if it did I'm not sure how safe the results would be.
No, it's not, and yes there are tools to do this. It is merely converting JIS race seat (27.0mm) to ISO dimensions (26.4mm) by removing 0.3mm of material.
Bike Tools Etc. offers several models but they're not cheap: http://www.biketoolsetc.com/index.cgi?id=316199216443&c=Tools&sc=Fork&tc=Crown-Race-Cutter-Sets
If this is a one-off project, you may be better served by having your local LBS do the work.
Crown race mills certainly exist, and this is a bread and butter job. It used to be that every decent shop had this mill since it was required to prep 95% of frames. Now they aren't so common any more, partly due to the change in the most popular steerer to 1-1/8", and also to changes in how forks are made.
The tools are still made, but I doubt you'll find one within your limited budget, as they're typically $250-300 or more new. Possibly you'll find a used one (look for a shop going out of business) but it'll be hard to gauge it's condition. If the cutter is OK but dull, figure $25-35 to sharpen.
toytech
09-06-10, 10:26 AM
From the links you provided I may already have it, the tool I have I was under the impression was for facing the top of the crown, I will take some measurements.
From the links you provided I may already have it, the tool I have I was under the impression was for facing the top of the crown, I will take some measurements.
The same cutter is used to face the crown as mill the diameter.
Think of it as the opposite of a drill. Rather than go through a donut to make a hole, a crown mill (holo-mill) removes the donut and leaves the "hole".
When you drill all the cutting is done at the bottom, and the diameter of the resulting hole is constant regardless of depth. A holo-mill works the exact same (but opposite) way, all the cutting is at the forward edge, and as it advances it leaves a pin of uniform diameter regardless of length.
toytech
09-06-10, 10:38 AM
Awesome. I bought a large box of professional shop tools a couple years ago and am constantly finding new stuff, and what some of it is for ;)
Bianchigirll
09-06-10, 10:53 AM
I believe the tools intended job is to simply face and square the crown race but it is used to cut it down. I think this may be a pricey tool though.
here is some info on the VAR tools for this http://www.sheldonbrown.com/var/pages/var0024.html
toytech
09-06-10, 10:57 AM
That is the one I have.
toytech
09-06-10, 01:41 PM
Mission accomplished, thanks to all.
Chris
Bezalel
09-06-10, 02:32 PM
I thought you were trying to reduce the diameter of your entire steerer, not just the race.
JohnDThompson
09-06-10, 04:30 PM
That is the one I have.
Make sure you have the proper size cutter. VAR made them for both JIS and ISO race seats; most were double-sided, many have JIS on one side and ISO on the other, some were the same on both sides.
toytech
09-06-10, 04:51 PM
Mine is double sided, 27mm on one side 26.4mm on the other. Came out very nice, thanks again.
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