Why does the campy bb facing tool also cut a chamfer?
#1
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Why does the campy bb facing tool also cut a chamfer?
I'm talking about this tool here:
Note that it will cut a chamfer into the bb - why exactly do we need this tool? Or is the description wrong? I only ask because the park facer is just a flat mill.
Note that it will cut a chamfer into the bb - why exactly do we need this tool? Or is the description wrong? I only ask because the park facer is just a flat mill.
#2
nice idea, poor execution
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That doesn't look like the original Campagnolo mill...
Perhaps it's the mill that chamfers the shell for a Mavic bb?
Perhaps it's the mill that chamfers the shell for a Mavic bb?
#3
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As a long-time machinist (started in '71), I can tell you that it is normal for all threads, external or internal to start with a 45 degree chamfer that is 1-2 thread pitches in depth. A straight surface leaves a weak partial thread that is of no value and makes it hard to get the mated parted started in straight.
Most parts with internal threads define the thread chamfer to be slightly larger than the major diameter of the thread.
I should add that the tool shown doesn't look like it would do both face and chamfer an ID, but I'd need to see the end of the cutter more closely.
Also, most facing jobs should only require a small fraction of one thread to be removed.
Most parts with internal threads define the thread chamfer to be slightly larger than the major diameter of the thread.
I should add that the tool shown doesn't look like it would do both face and chamfer an ID, but I'd need to see the end of the cutter more closely.
Also, most facing jobs should only require a small fraction of one thread to be removed.
Last edited by DaveSSS; 01-06-10 at 08:25 AM.
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What DaveSSS said makes sense, but that tool does look very much like Mavic's BB chamfering tool.
the 80's/90's Mavic sealed cartridge BBs do not use the bike's BB threading to anchor itself to the frame. It does it with just pressure from 45 degree faced lockrings on both ends of the BB that will seat on to the chamfered faced BB provided by the Mavic tool. A nice idea that would have eliminated all need for trying to figure out what threading your BB is when it comes time to change your BB, but I suspect Mavic wasn't too generous with sharing the patent and technology for this with other companies and it "Betamaxed" itself out of existence, plus other better(?) BB designs came to be afterwards ......although,.......don't Phil Wood BBs kinda work the same way??
Chombi
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the 80's/90's Mavic sealed cartridge BBs do not use the bike's BB threading to anchor itself to the frame. It does it with just pressure from 45 degree faced lockrings on both ends of the BB that will seat on to the chamfered faced BB provided by the Mavic tool. A nice idea that would have eliminated all need for trying to figure out what threading your BB is when it comes time to change your BB, but I suspect Mavic wasn't too generous with sharing the patent and technology for this with other companies and it "Betamaxed" itself out of existence, plus other better(?) BB designs came to be afterwards ......although,.......don't Phil Wood BBs kinda work the same way??
Chombi
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85(?) Vitus Plus Carbone 7
Last edited by Chombi; 01-05-10 at 06:00 PM.
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I agree with Helomatic I do not think that is the "facing" tool. also what Dave and Chombi said are correct too if you are dealing with a Mavic cart BB (I think VO just came out with one)
now to answer your question about the too. the 'facing' cutter should not chamfer the BB shell but it is designed to remove paint and "square" the sides of the BB to ensure they are parrallel. this aids in getting the fixed cup tightly into place as well and making the lockring lock tighter. 'facing' and 'chasing' was standard practice on all frame (build up in shops anyway) and I normally did it ( atleast facing) on overhauls. there is also a tool for 'facing' the headtube as well.
now to answer your question about the too. the 'facing' cutter should not chamfer the BB shell but it is designed to remove paint and "square" the sides of the BB to ensure they are parrallel. this aids in getting the fixed cup tightly into place as well and making the lockring lock tighter. 'facing' and 'chasing' was standard practice on all frame (build up in shops anyway) and I normally did it ( atleast facing) on overhauls. there is also a tool for 'facing' the headtube as well.
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#7
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Just a slight correction. Facing makes the face of the BB shell perpendicular to the threads and insures that the face is truly flat, if the cutting is done carefully. I've never had it done to a frame in 25 years and over a dozen frames.
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The cutting bit comes off, right? Maybe it's missing a flat one.
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Look for markings on the cutter; if it's actually a Campagnolo cutter, it should say so:
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I'll be glad to get that useless Mavic BB tool out of your hands Pronto!
Chombi
Chombi
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Just a further off topic interjection, the VO BB fulfils the same niche as the Mavic (reviving frames with buggered up, or obsolete BBs) but does so in a way that doesn't involve cutting on the bike of any sort.
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#14
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For example, modern bb's like phils and sugino 75's are very intolerant of shell face misalignment. I've seen a fresh steel frame so bad that a standard shimano square taper cart sat noticeably off because of facing issues with a bb.
At any rate, I have that exact same cutter on that tool, that would be quite a coincidence if it is in fact the mavic tool.
#16
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What I do to check for the need to face a BB shell is install the cup and thread it in until it touches a .010 inch feeler gage. Then I use feelers in the .008-.012 inch range to search for high or low areas. If any area exceeds those limits, I'd face the shell. Always remove any paint from the face of the shell, first.
Anyone installing a Campy UT crank should do this and then measure the BB shell width, which must be 67.2-68.8mm to work properly. A lot of failures result from failure to do one or both of these procedures.
Anyone installing a Campy UT crank should do this and then measure the BB shell width, which must be 67.2-68.8mm to work properly. A lot of failures result from failure to do one or both of these procedures.
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All repeated facing accomplishes is to narrow the bottom bracket shell until the bottom bracket doesn't fit properly. Do it once (only if needed) and leave it alone after that.
My experience mirrors DaveSSS's. I've built up three Litespeeds Ti frames and a Co-motion steel frame from scratch as well as bottom bracket replacements on several other bikes and none of them has needed facing.
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I hope you don't do it for every overhaul of frame that has been faced properly once. Once a frame is properly faced, it should never need it again unless it is repainted and then only to clean up any overspray.
All repeated facing accomplishes is to narrow the bottom bracket shell until the bottom bracket doesn't fit properly. Do it once (only if needed) and leave it alone after that.
My experience mirrors DaveSSS's. I've built up three Litespeeds Ti frames and a Co-motion steel frame from scratch as well as bottom bracket replacements on several other bikes and none of them has needed facing.
All repeated facing accomplishes is to narrow the bottom bracket shell until the bottom bracket doesn't fit properly. Do it once (only if needed) and leave it alone after that.
My experience mirrors DaveSSS's. I've built up three Litespeeds Ti frames and a Co-motion steel frame from scratch as well as bottom bracket replacements on several other bikes and none of them has needed facing.
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The text describes it as "adaptable to Italian tool holders" by which it likely means "Campagnolo."
You can see that it bears little resemblance to the Campagnolo #725 bottom bracket facing mill:
But it does strongly resemble the cutter in your original picture.
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Regardless of the situation - facing the bottom-bracket is becoming essential with any frame - due to the external- BB's becoming more and more popular. But a notice should be with the bicycle to identify this task having been accomplished.
I can just see Joe bringing his bike for help - and the BB-shell is 58mm......
I can just see Joe bringing his bike for help - and the BB-shell is 58mm......
#23
nice idea, poor execution
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A competent mechanic can find said notice on the bottom bracket shell itself. If they can't tell the difference between a properly faced bottom bracket shell, and one that needs facing, they shouldn't be anywhere near that tool.
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HillRider wether I faced the BB on an overhaul depended on the bike of course. if it was one of our bikes and the faces were relativly clean I ight not. if it was an older mid to higher end bike and I was installing a new BB I certainly would.
and yes facing is a very delicate operatin like turning brake rotors. actually in most cases very little if any frame material is removed.
and yes facing is a very delicate operatin like turning brake rotors. actually in most cases very little if any frame material is removed.
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