Is there a tolerance for the upper size I could possibly machine my front brake hub to, back from powder coaters and I would like to re-machine the braking surface as the corrosion was considerable when I first had the bike, I've the perfect oppurtunity to turn the inner hub but would like a guide if there is any tolerance I should be wary of?

email (option): 79aust@sky.com

Hi Julian...The hub diameter when new is 7.015"-7.020" but the thickness of the hub is only .176". The acceptable limit at overhaul is 7.040" in the WD standards book for the M20, so you have very little to play with.
You might get away with pushing this limit by .010"-.020" but you risk hub distortion.
The standards book states that if the hub will not clean up at the upper limit shown it should be replaced....Ian

email (option): ian@wright52.plus.com

Julian

The 1954 standards book says for the front brake in inches:-

High 7.020
Low 7.015

Acceptable on overhaul 7.040

If the drum is badly scored and will not clean up to 7.040 renew drum (replace).

Does that make sense?

Rob

email (option): robmiller11@yahoo.co.uk

"snap"

Rob

email (option): robmiller11@yahoo.co.uk

"crackle"....Ian

email (option): ian@wright52.plus.com

It's right at the top end (178.80mm) will give it a go and if I get to much vibration then I guess it will have to be changed.
It is a very tight tolerance and find it difficult to believe that it can be so critical as the hub was quite distorted when I started cleaning off the powder coat.
The hub had to get sand blasted originally to remove all the rust that can be seen on my before photo.
The wheel looks completely transformed now its been machined but I'm a little concerned over the size

Before:


After:

email (option): 79aust@sky.com

Is there such a tight tolerance on the rear sprocket as mine may also benefit from a clean up if tolerances allow.
As I also don't want it to "Pop".

Julian

email (option): 79aust@sky.com

Is there any experience with spraying metal, plating or sleeving hubs? When restoring my Triumphs I had some deeply pitted fork legs that received several copper coatings to fill the pits, were ground to size and hard chrome-plated afterwards. Expensive, but still cheaper than new ones.

email (option): viaconsu [at] planet [dot] nl