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MG MGA - MGA layshaft oil hole question

Hi folks. I am rebuilding a spare transmission for my 1500 roadster. I have fitted four (instead of the usual three) needle bearings to the laygear. Now, I need to drill an extra oil feed hole in the layshaft, to feed the extra needle bearing. I went to a couple of local machine shops to inquire about having the necessary hole drilled. Both shops state that they dont have equipment that is capable of drilling a hole in the hardened layshaft! One machinist stated that only a specialized electric metal burning unit would be able to add the hole I need in the layshaft! Has anyone had any experience with drilling an extra hole in a layshaft, or know about the electric gizmo that burns such holes? Any thoughts or ideas are appreciated. I have considered using a small diameter abrasive dremel wheel to cut a small slot in the layshaft, instead of an oil hole. If the slot was angled across the layshaft, the needle bearings should probably be able to navigate across the slot. Any comments on the workability of such a modification? thanks, Glenn
Glenn Hedrich

The process is called Electrical Discharge Machining, or EDM for short. It is used a lot in the Tool and Die trade. You might try a local Die making shop and see if they would take on a small job like that. It's not a complicated process but it requires an EDM machine to do it.
Ed Bell

EDM is a usually specialty business. If you can't find an EDM shop in the yellow pages, any machine shop should be able to tell you where to fine the EDM shop.

Putting a hole in the layshaft doesn't necessarily require EDM. A cobalt drill bit and a drill guide should do it. It may be easier if you grind through hard surface layer first with a small stone in a Dremmel. You may need to also increase depth of the oil supply hole in the end of the shaft to reach the new radial hole. Do NOT make a slot in the surface.

I have assembled a few of these without adding the 4th radial hole. So far no reports of premature failure. I have run one enough miles to wear out a new layshaft again, using the inadequate 11-roller cage bearings). I may never use the 11-roller bearings again. The original type full compliment needle bearings are far superior for extended life.
Barney Gaylord

Thanks for the comments. Barney: Does that mean the layshaft is case hardened? Any idea how deep the "hard layer" of metal might be? Thanks, Glenn
Glenn Hedrich

Judging from the ones that are worn, the surface hardness is not very deep. Maybe 0.010" if you're optimistic before it's soft enough to be negligible. I never put a hardness tester on one, but see attached picture. When you get a new shaft, run a file across the OD near one end (non-bearing surface). If the file scratches it, send it back.

Barney Gaylord

Glen, rather than fitting a 4th bearing I opted for fitting 20 rollers as used on the first motion shaft. These rollers are about 50% longer than a standard bearing and you do not need to drill extra holes !! Use the end plates from your old bearings, cut spacer tube to length and hey presto - you have a bearing that will take 50% more load than the original loose roller bearing.
A J Dee

Hi Glenn. How did you lengthen the rear laygear bore?
Art
Art Pearse

Hi Art. I lucked into an inexpensive laygear on ebay. When I checked the bore, I found it was already machined enough to fit 2 sets of needle bearings. Dont know if it came from the factory this way, or wheter it was machined post factory production. Interesting question though Art! Cheers, Glenn
Glenn Hedrich

This thread was discussed between 14/10/2010 and 16/10/2010

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