Topic: Rear Wheel Bearing Retainer Thread Size?

[jtsmith]

Hi all,

I have a '75 CB750K, and I was wondering if anyone knew the thread size of the inside bearing retainer (23 in attached figure) for the rear wheel?

I was replacing the wheel bearings when the hammer decided it had enough of my shenanigans and decided to strike the female threads on the hub. Now I need to run a tap through them to clean them up to re-install the retainer.

In case you were wondering, yes, it was "one last hit to make sure the bearing is set" that did it. Lucky me!

Thanks all for the help. Without this forum I would have never even made it this far!

Cheers,
JT

ps, I have searched a ton for this info, but can't seem to locate it.

[CycleRanger]

I buggered up a few of the top threads when I removed the retaining ring.  (I had to chisel/cut out the old one.)
I got a new retaining ring and used it to clean up the threads by greasing it up and slowly, carefully working it in a few threads then backing it out and repeating until I got past the buggered threads. The new retaining ring "straightened" the threads and I was able to seat the ring.

This may or may not work in your case, depends on how far down and how many/badly the threads are damaged.
To find a tap that large to chase the threads you may have to visit a machine shop.

Good luck! 

[jtsmith]

I buggered up a few of the top threads when I removed the retaining ring.  (I had to chisel/cut out the old one.)
I got a new retaining ring and used it to clean up the threads by greasing it up and slowly, carefully working it in a few threads then backing it out and repeating until I got past the buggered threads. The new retaining ring "straightened" the threads and I was able to seat the ring.

This may or may not work in your case, depends on how far down and how many/badly the threads are damaged.
To find a tap that large to chase the threads you may have to visit a machine shop.

Good luck! 

Thanks for the advice CR. I have also seen where people just 'dremeled' out the bad part. Fortunately it is just one section (hammer strike), but it is pretty bad. I think I can clean it up to a point where your technique should work.

[MCRider]

i'VE READ THIS SUGGESTION FROM OTHERS HERE (darn caps lock) and this is how you do it. The thread pitch is likely a 1.5, which is metric fine. That is 1.5 threads per mm. Most metrics are 1.0 (like the 6mms) and 1.25, like many of the 8 and 10mm bolts. The retainer is obviously finer. A thread gausge from a tap and die set will tell us for sure, but its not magic. I'll look this weekend myself. 

Then you take any diameter tap that is a 1.5mm pitch. Then rub it into the nicest part of the remaining threads in the hub, and while holding it in place, force it with a small hammer or such into the offending threads, back out and force again, over and over, straightening out the threads as you go.  The idea being you don't need a tap the diameter of the hole. That would indeed be a piece of work. Just one of the correct pitch would work. The larger the better, but that's for being able to hold it.

Intriguing idea as i have a "ruined" hub and would love to reclaim it, for sale if nothing else.

[jtsmith]

i'VE READ THIS SUGGESTION FROM OTHERS HERE (darn caps lock) and this is how you do it. The thread pitch is likely a 1.5, which is metric fine. That is 1.5 threads per mm. Most metrics are 1.0 (like the 6mms) and 1.25, like many of the 8 and 10mm bolts. The retainer is obviously finer. A thread gausge from a tap and die set will tell us for sure, but its not magic. I'll look this weekend myself. 

Then you take any diameter tap that is a 1.5mm pitch. Then rub it into the nicest part of the remaining threads in the hub, and while holding it in place, force it with a small hammer or such into the offending threads, back out and force again, over and over, straightening out the threads as you go.  The idea being you don't need a tap the diameter of the hole. That would indeed be a piece of work. Just one of the correct pitch would work. The larger the better, but that's for being able to hold it.

Intriguing idea as i have a "ruined" hub and would love to reclaim it, for sale if nothing else.

Hey MCRider,

Thanks for the advice! I finally got around to measuring the pitch, and you are correct, 1.5mm. I will go buy a tap and give this a try.

Cheers,
JT

[david 750f]

I agree with MCRider's method but would like to clarify his pitch size comments.

In the metric measurement system the pitch size is the width between threads. For any diameter bolt a 1mm pitch size is the same width. i.e a 1mm is always a FINER pitch than 1.5mm .

In the standard system the pitch is again the distance between threads. i.e a 1/4-20 bolt will have 20 threads per inch or 1/20th (.050) of an inch between threads.

Here is a photo of a 1.5mm pitch guage (top) and a 2.5mm pitch guage (bottom).

Hope this hasn't confused the issue.

[MCRider]

Wow, I flunked that test big time! Thanks for the polite corrective action.

I was correct the retainer is a 1.5 but not correct in thinking it was a finer pitch than that. And by finer, that would be 1.25 or 1.00.

Funny how one can wallow in misinformation until its time to actually use it.

Thanks again.