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1980's 12 speed bent axle replacement - weird threading?

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1980's 12 speed bent axle replacement - weird threading?

Old 03-20-23, 06:03 PM
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1980's 12 speed bent axle replacement - weird threading?

Bike in question is a 1980 Fuji Gran Tourer SE

tl;dr summary
- overhauling rear hub, first time
- see rear axle is bent
- hmm let's replace
- old axle takes m10x1 nuts, that seems right
- get m10x1.0mm threaded axle replacement from LBS
- old cone and locknuts don't fit on this new axle (??)
- caliper shows new m10 axle diameter (9.9 mm) is larger than my OEM bent axle (9.5 mm)
- what spec'd axle do I need to order to match my old cone/locknuts?


while overhauling (first time) the rear hub I noticed the axle had a bend in it. The old bent axle seemed to be M10-1.0 threading, tested with like nuts, so I went to my LBS and asked for a replacement specifying m10x1.0mm spacing and got one. Come home and the original cone nuts and lock nuts from my old axle won't thread - the m10x1.0 was too big for them

I put my cheap digital caliper (+/- 0.2mm accuracy I think) on each axle around the threads and the m10 I got from my LBS says expected 9.9 mm, the old original axle gives a pretty firm 9.5 mm. The new m10 axle works well with nuts of that size so I know it's fine. What's the deal with the old '9.5 mm' axle? '3/8 inch = 9.525 mm, so I try some 3/8" nuts on the old (9.5 mm diameter) axle and they won't thread either - the axle is too big for them, they wont go on. Tha heck?

Note: I got new NOS ebay replacement cones to replace the heavily pitted originals (and new bearings) which are within 1mm length/spacing wise of the old cones and seem to fit pretty well with the original dust caps. My LBS didn't have any old locknuts, m10 or otherwise, so I feel constricted to the threading/diameter axle to fit my old original lock and cone nuts. I'm also trying to reuse them to maintain the same spacing, and tbh because I trust parts that lasted over 40 year more than new ones


Other observations:
- the original cone nuts were slightly wobbly on the original axle
- the original LOCK nuts were as snug as could possibly be on the original axle
- measured the interior diameter of the oem original lock nuts with the caliper and got 8.5 mm
- I ordered replacement cones that are m10 and fit on the new axle AND old axle, but are (expectedly) more wobbly on the narrower original axle


I saw on ebay what appear to be 9.5mm diameter vintage axle replacement but I'm not so sure. Thoughts? Can provide images of anything if helpful

Last edited by fjifu; 03-20-23 at 06:41 PM.
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Old 03-20-23, 06:13 PM
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https://wheelsmfg.com/products/hub-p...s/axle-11.html

26 TPI is EXTREMELY close to 1mm thread pitch.
0.03846" vs 0.03937"
10mm Metric nuts will "fit" the the 9.5mm x 26 axle, but not the reverse.
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Old 03-20-23, 06:35 PM
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Originally Posted by Bill Kapaun
https://wheelsmfg.com/products/hub-p...s/axle-11.html

26 TPI is EXTREMELY close to 1mm thread pitch.
0.03846" vs 0.03937"
10mm Metric nuts will "fit" the the 9.5mm x 26 axle, but not the reverse.
Is there a cheap nut or component I can buy to confirm 9.5 x 26 TPI threading?

re: your link, I've always wanted to convert the rear wheel of this era of bike to a quick release. Got to sort out these issues first though, get it re greased, re bearing'd and set up right on its own terms
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Old 03-20-23, 07:22 PM
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The usual way to check for an axle's threading is to test fit known nuts or cones on it. That didn't happen the first time at the LBs, or at least I'm assuming not done by the LBS when they sold you what you asked for. Did you have the old bent axle in hand when you were there?

9.5 is an axle diameter that have been made for many decades in 24TPI, 26TPI and 1mmpt. Do you know yet which pitch your old axle is? The other method for helping to determine axles is a thread pitch gage. Over the many threads that the gage will contact the slight differences between 26tpi and 1mmpt are able to be seen. The 24tpi should be pretty obvious and is generally limited to coaster brake hubs.

9.5 (3/8) QR axles are out there but are less common then the current "Asian" size of 10x1. Do check the hub's bearing cups for condition before spending much $ of this hub. Also check the alignment of the frame's rear drop outs incase they are not parallel and helping to load the axle without any riding stresses even happening. Andy
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Old 03-21-23, 12:20 AM
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I have a local bike shop that has a little display of several axles and several cones, all with different threading. You just try your axle or cone or whatever you have on the different labeled options until you know exactly what you've got.
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Old 03-21-23, 08:32 AM
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Originally Posted by fjifu
Is there a cheap nut or component I can buy to confirm 9.5 x 26 TPI threading?

https://www.amazon.com/HOAOH-Stainle...-4904355?psc=1
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Old 03-21-23, 01:26 PM
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Originally Posted by JohnDThompson
FWIW: can't speak for other locations, but in my area the local Lowe's was also a source for thread gauges.

When I got mine, it turned out the nearest Lowe's had both metric and Imperial thread gauges in stock. As I recall I ordered them online and picked them up a couple of hours later.

If you can't/don't want to wait for Amazon delivery, that might be a workable option.
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Old 03-21-23, 01:49 PM
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When measuring an axle's threaded diameter remember that the threads are not cut/formed completely. Their tips and valleys are somewhat flattened/rounded (depending on the thread "standard"). So a diameter reading on the threaded portion will result is slightly less than the "claimed size". Another aspect of thread forming for axles and how to measure them is that many have their threads formed by rolling, a process that uses thread form shaped tools to push and displace the axle's surface. In these cases the unthreaded central section of an axle will measure quite a bit less than the thread's size. The tops of the thread forms have been plowed up from the initial surface.

As thread forming tools wear and need periodic adjustment (thread rolling specifically) and these needs are not always followed up on by factories the actual tolerances of dimensions and how almost but not exactly the same parts can fit together can be hard to discern. This is one reason why the Wheels Manufacturing (started out as Wheels of Boulder) company has offered an axle thread testing board. A collection of the common axle threads with a stud to test the nuts and a sleeve to test the axles. It is very helpful and easy to let a customer use too. But the absolute best test are the original parts. Andy
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Old 03-29-23, 04:35 PM
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Thanks all for the advice. Andy I recently came upon your decade (!) old thread while looking up how to straighten a bent steel fork. (topic for another thread!) I want to thank you for the effort and time you put into those posts.

Originally Posted by Andrew R Stewart
The usual way to check for an axle's threading is to test fit known nuts or cones on it. That didn't happen the first time at the LBs, or at least I'm assuming not done by the LBS when they sold you what you asked for. Did you have the old bent axle in hand when you were there?

9.5 is an axle diameter that have been made for many decades in 24TPI, 26TPI and 1mmpt. Do you know yet which pitch your old axle is? The other method for helping to determine axles is a thread pitch gage. Over the many threads that the gage will contact the slight differences between 26tpi and 1mmpt are able to be seen. The 24tpi should be pretty obvious and is generally limited to coaster brake hubs.
I brought the original axle in but incorrectly thought it was m10x1 since those are the nuts I had, which I knew the threading of, that closest fit it, so I asked for that and got it. Recently I went again to the LBS, with the original axle and nuts and the m10 one I bought from them earlier to ask for an exchange (it was my bad) and, since they couldn't find it, asked if they could tell me the size/threading pitch so I know what to look for but unfortunately they were two young guys who weren't really familiar with it I think. One told me to test it at Home Depot, which I was going to anyway for something else, and sure enough the axle didn't fit in any. It was somewhere between 3/8" (wouldn't fit) and m10x1 (fits but loose). ???

I don't have the m10x1pitch axle anymore to test visually next to the old axle

Originally Posted by Andrew R Stewart
As thread forming tools wear and need periodic adjustment (thread rolling specifically) and these needs are not always followed up on by factories the actual tolerances of dimensions and how almost but not exactly the same parts can fit together can be hard to discern.
I found it strange that the original cone nuts, which I assume were original since they fit with the dust cap, are noticeably wobbly when on the axle when pressed between two fingers. The locknuts however like I said fit great and removed the slack. I ordered NOS cones from ebay that were within added 0.7 ~1mm length of the original, keeping spacing in mind, and they had the same wobbliness, which was addressed by backing the locknut onto it like the presumed originals, so I presumed it to be ok. Not as sure now

I read about sanding down the cones here with axle attached to power drill + incrementally higher grit sandpaper to get past the pits and smooth it out. Case hardened vs through hardened was the issue other posters here debated, not knowing for sure what hardening your cones are. But some claimed it worked for them - and I read a blog recently where someone who used this method on old cones claimed "He even put the repaired cones to the test for a year (about 14.000 kms) and the cones seem to be holding up perfectly!" - Anyone have experience with this?

I almost wonder if I could get something like the below ebay link, with expected potential problems of the spacers not matching, or my original dustcap is too big or small, and that I might have to file the dropout to get it to fit.
https://www.ebay.com/itm/304760164866

And lastly to go along with the desperate last resort,
. I'm sure that won't be widely recommended but I am curious what others think

Last edited by fjifu; 03-29-23 at 10:15 PM.
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Old 03-30-23, 08:58 AM
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Interesting vid but it has some less than right info. Steel gets stronger at the bend BUT it looses the quality of elongation. As in the steel becomes more brittle. bend a paperclip back and forth a few times and note that the bent section won't re bend as easily as the adjacent un bent section. But the clip will break at the bend anyway because that section has lost the ability to absorb the stresses of the bending attempts without cracking.

The reason why the baby jogger axle bent even though it is of thicker section than a bicycle axle is because the jogger axle is cantilevered from one end, a bicycle axle is supported at both ends. However on many rear hubs the bearings are not evenly placed along the axle so the bending forces are greater at the bearing closer to the axle's center (this bearing location allows the freewheel to fit).

While a high impact force (riding off a curb) will stress an axle so too will misaligned drop outs. So too will hitting a pot hole (a far more common incident than a curb drop off).

It's sad that learning how to figure mechanical stuff out is not taught by most schools or jobs. They do teach how to pass the test, but that is more about memorization than about the interactions and relationships between the parts in a mechanical system. As the method of repair, in a bike shop and elsewhere, has gone to replacing complete parts (like a wheel) from just replacing the offending sub part (the broken axle) the skills of threading identification has also been lost (or never learned). What's even worse (but not exactly said by the OP) is that the shop kids didn't seek help from a more informed coworker. Andy

I strongly suggest that riders don't try to shift all their weight to the front wheel when riding off a curb, unless your helmet includes facial protection (like a full face helmet or a football one)... One can pull up on the handle bars to unweight front wheel and then rock forwards to reduce the rear wheel "weight" BUT KEEPING THEIR FEET ON THE PEDALS. So some weight is on those pedals all the time. This gives the rider far more control then if there was no weight on the pedals, as in when all your weight is on the front wheel only. Andy
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