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Bottom Bracket as Die for Hub Boss?

Old 11-29-18, 03:23 AM
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Bottom Bracket as Die for Hub Boss?

I have a Campagnolo Record hub with some sort of problem with the threads on the boss. I've tried 5 different freewheels (4 Suntour, 1 Shimano) and just one will thread all the way on. The other 4 bind after 3 or 4 turns, much as Sheldon Brown describes French threaded freewheels as doing on a BSC (1.370" x 24 tpi) hub boss. I've tried the freewheels that won't fit on an old Airlite hub and they thread on fine.

I've tried cleaning the hub threads with a brass brush but to no avail. I've search the internet for a hub boss die but no one seems to sell them. Then I realised that BSC bottom brackets are the same 1.370" x 24 tpi as the hub boss. Would it be sensible to try cleaning up the hub threads in a bottom bracket?
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Old 11-29-18, 03:44 AM
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I would not try that at all. Dies and taps are made from steel that is designed to cut. Bottom bracket shells are not, plus the threads in the shell typically are full of grit.

What I do for poor threads is look closely to see what the problem could be. Usually thread issues are caused by crud trapped in the teeth. A wire brush can help, but in my experience is not fine enough to clean everything out from the grooves. I use a dentist’s pick with a very fine point to clean out as much as I can. That also will indicate whether any of the threads are bent or flattened.
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Old 11-29-18, 08:13 AM
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Campagnolo hubs are marked with the thread spec. Starting in the late 70s, the thread spec was explicitly stamped into the space between the hub flange and the threads themselves. Earlier hubs used the presence or absence of inscribed grooves in that space to indicate thread spec:


Source: Sutherland's 4th Edition

An English thread bottom bracket lockring should be able to thread onto an English thread hub. If it does not, or if the threads are visibly damaged, you could clean them up with a thread file:



This would not restore destroyed threads, but may at least make the hub serviceable.

Last edited by JohnDThompson; 11-29-18 at 08:17 AM.
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Old 11-29-18, 09:28 AM
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Well lets explore this. One could buy a Bb shell, so that no frame was harmed in doing this experiment. One could then grind cutting edges into the threads at a couple of locations within the shell and reduce the lead in thread for easier initial engagement. Then it could be hardened, although if the hub shell is AL I question this requirement. Then keeping the shell coaxial to the hub's threading, chase away.

I'm no tool designer but I suspect that the clearances that are in a female threaded "nut" to allow the male to freely fit will, if used as a thread chaser, result in too tight a fit for a male "bolt". Andy
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Old 11-29-18, 09:39 AM
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I would look closely at the Campy hub threads, which are aluminum, to see what or where the issue is. For my old eyes, i would use some magnification. It is probably only a small area of one thread, though obviously it could be more. I would then use a fine file (jewelers file?) and clean it up. I just did this with the threads on a fork for a buiild i am doing. Be patient, you will get there.

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Old 11-29-18, 10:41 AM
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+1,the thread file is a tool for the purpose, as mentioned above

+2, adjustable cup lock ring on the left side of the BB is right hand thread ,
like hubs use.

& needle files may be useful .. a set has a number of different shapes in them..
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Old 11-29-18, 11:14 AM
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Originally Posted by Andrew R Stewart View Post
Well lets explore this. One could buy a Bb shell, so that no frame was harmed in doing this experiment. One could then grind cutting edges into the threads at a couple of locations within the shell and reduce the lead in thread for easier initial engagement. Then it could be hardened, although if the hub shell is AL I question this requirement. Then keeping the shell coaxial to the hub's threading, chase away.

I'm no tool designer but I suspect that the clearances that are in a female threaded "nut" to allow the male to freely fit will, if used as a thread chaser, result in too tight a fit for a male "bolt". Andy
(A BB shell or an old freewheel.) Don't forget to de-burr the cutting edges after grinding -- not easy.
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Old 11-30-18, 01:29 PM
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Originally Posted by Andrew R Stewart View Post
Well lets explore this. One could buy a Bb shell, so that no frame was harmed in doing this experiment. One could then grind cutting edges into the threads at a couple of locations within the shell and reduce the lead in thread for easier initial engagement.
Might be cheaper/easier to take a bottom bracket lockring and grind a couple chip channels into it. We're just chasing the threads, after all, not cutting fresh threads.
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Old 11-30-18, 04:05 PM
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I wasn't being sincere in my suggestion of using a BB shell as a chaser. I guess I should have made that better known. Andy
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Old 11-30-18, 06:30 PM
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So far I've been mostly ignoring the French stuff.

For taps, they have thread chasers which are designed to have very little cutting, and mostly reprofiling the existing threads. You don't want to take more off of already bad threads.

Thus the grooved BB shell (or a junk freewheel) might be the way to go.

And, in the end, you want a tight fit.

The BB lockring may well thread on all the way as it only catches a few threads, and is not subject to issues of thread creep.

Here is Sheldon Brown's Freewheel page & BB page:
https://www.sheldonbrown.com/freewheels.html
https://www.sheldonbrown.com/cribshe...mbrackets.html

For freewheel:
Italian 1.378" x 24 tpi
ISO 1.375" x 24 tpi
British 1.370" x 24 tpi
French 1.366" x 25.4 tpi

So, if the hub is Italian, an ISO or British freewheel may simply be tight.

If the hub is French, then the threads run afoul. If you have say 3/4" of threads, you'll be off by about 1 full thread by the time you screw the freehub on. Anything you do to try to remedy that could well destroy the threads instead. And, you're also left with the issue that French will be about 0.01" smaller than ISO, so if you get the threads right, the freehub may end up loose.
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Old 11-30-18, 06:39 PM
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Old 12-05-18, 02:50 AM
  #12  
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Originally Posted by JohnDThompson View Post
Campagnolo hubs are marked with the thread spec. Starting in the late 70s, the thread spec was explicitly stamped into the space between the hub flange and the threads themselves. Earlier hubs used the presence or absence of inscribed grooves in that space to indicate thread spec:


Source: Sutherland's 4th Edition
Well, I never! This hub has no groove between the flange and the threads, thus it is not BSC threaded. Many thanks for the info, John. I've just checked another spare Campagnolo hub I have and it has the groove. I'd never realised this. I have Campagnolo hubs on 2 other bikes which I've changed the freewheels on without trouble so they must be grooved, too.

Thank you to everyone who took the time to reply. Thanks to Aubergine (shouldn't that be 'Eggplant'? In Seattle, if not in Reims..) I have a much examined and clean threaded non-BSC hub - I went at it with a dental pick, at their suggestion, and now know the threads are nice and clean... and undamaged. From what I've read this hub must be French threaded as if it was Italian a BSC freewheel should go on.

Please excuse my late reply. I was thinking of using this hub (one of a pair) on a bike I'm building for a friend but then, after I'd posted about the rear hub threads, discovered that the 100mm OLD of the front hub was too big to fit in the 95mm front forks. So is the rear, actually, but I was going to cut the axle down to fit in the 110mm rear space - the frame is a 1954 Hetchins - and use a 3-speed block. Not period-correct but my friend isn't at all concerned about that.

I have several nice 32/40 hole period hub sets but my main concern was being able to use 700c rims for the far wider tyre choice they offer and they are mostly only available with 36 holes - with original spec 27" rims you're pretty much restricted to Panaracer Pasellas at low pressure. The only modern 40 hole/700c rims I'm aware of (made by Velocity) are a bit too wide, as well as being expensive for what they are (without spoke sockets). I then discovered that what I'd assumed was a 40-hole 1949 Sturmey Archer hub I had in a drawer actually had 36 holes (I bought it 10 years ago from a seller in France) so we are using that with a nice 32 hole British Hub Company Solite on the front.

Thanks again, everyone!
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Old 12-06-18, 04:01 AM
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Further to the above, it seems this hub has Italian threads. They measure 35mm across, which according to Sheldon Brown's figures is the Italian size. According to the same figures French threads measure 34.7 while a known English hub I have measures the correct 34.8mm.

I've just checked the freewheels I have. They all fit the British hub and yet one of them also fits this non-British hub. As far as I can tell it fits the same on both - threading on and off easily with no discernible difference in fit. Can anyone suggest why this might be? The freewheel in question is a late model Suntour 6-speed with ramped teeth. The others are all earlier 5-speed Suntours.
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Old 12-06-18, 04:19 AM
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Originally Posted by Dawes-man View Post
Further to the above, it seems this hub has Italian threads. They measure 35mm across, which according to Sheldon Brown's figures is the Italian size. According to the same figures French threads measure 34.7 while a known English hub I have measures the correct 34.8mm.

I've just checked the freewheels I have. They all fit the British hub and yet one of them also fits this non-British hub. As far as I can tell it fits the same on both - threading on and off easily with no discernible difference in fit. Can anyone suggest why this might be? The freewheel in question is a late model Suntour 6-speed with ramped teeth. The others are all earlier 5-speed Suntours.
Originally Posted by CliffordK View Post
Here is Sheldon Brown's Freewheel page & BB page:
https://www.sheldonbrown.com/freewheels.html
https://www.sheldonbrown.com/cribshe...mbrackets.html

For freewheel:
Italian 1.378" x 24 tpi
ISO 1.375" x 24 tpi
British 1.370" x 24 tpi
French 1.366" x 25.4 tpi

So, if the old freewheels are "British", and the mystery hub is "Italian", they will be off by about 0.01". Not that much, but apparently enough to cause an issue.

On the other hand, if the new freewheel is "ISO", then the difference may be 0.003", or about 1/3 the difference with the English freehubs.

And, that difference is apparently just enough to make it work with one, and not the other.
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Old 12-06-18, 07:32 AM
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Originally Posted by CliffordK View Post
So, if the old freewheels are "British", and the mystery hub is "Italian", they will be off by about 0.01". Not that much, but apparently enough to cause an issue.

On the other hand, if the new freewheel is "ISO", then the difference may be 0.003", or about 1/3 the difference with the English freehubs.

And, that difference is apparently just enough to make it work with one, and not the other.
Thank you, Clifford! That explains everything. So the later freewheel must be ISO. I've just re-read Shelton Brown's comment about 'all later hubs' being ISO... I'd missed the relevance of that the first time.
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