Myford ML7 Spindle Problem

I have recently acquired a 1949 Myford ML7 lathe. There seems to be a problem with the spindle and backgear. If I engage the backgear the whole machine seizes up solid, even when the backgear key is removed.

My understanding of how the backgear works is that normally the Vee Cone Pulley Assembly is free to rotate on the spindle. Drive to the spindle is via the Backgear (bullgear) with the key engaged. To use the backgear one should undo the key and engage the backgear cluster with the lever. I stand to be corrected if I've misunderstood the method of operation.

I've removed the whole spindle from the headstock and the Vee Cone Pulley and backgear are locked on tight. I can move nothing. I did notice however that there was no oil nipple in the Vee Cone Pulley as shown in the exploded parts diagram. Instead there was a grubscrew deep inside the middle pully apparently locking the Vee Cone Pulley to the spindle. This can't be right - can it? Even after removing this grubscrew everything is still locked up tight.

Is this a bodge by some previous owner? How do I go about seperating the Vee Cone Pulley from the spindle?

Thanks,

James

hi James,

An good explanation by david of the ML7 back-gear here:

http://iwr.ru.ac.za/~iwdf/lathe/backgear.html

The pulley is certainly sized by lack of lube,

another common problem is a separation of the pulley and is gear (press-fitted)

Further dismantling will requiring a Press

pierre

The belt turns the pulley arrangement on the lathe headstock and the first cog in the gear, this small cog attached to the end of the pulleys turns freely around the spindle when disengaged from the bullgear or spindle(depends on system)

This small cog on the end of the pulleys drives the big backgear cog, which transmits directly along to the small backgear cog

The small backgear cog then drives the bullwheel, which is fixed to the spindle and therefore turns the spindle slowly but with huge torque

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Is this a bodge by some previous owner? How do I go about seperating the Vee Cone Pulley from the spindle?

A serious bodge, your initial conclusions are correct and the pulley must be at least capable of revolving independently around the spindle

Removal... I wouldn't know about, in theory it should pop right off the spindle if the locking grubscrew is released

I would wait for any users of this old machine to reply before getting too ambitious

http://www.lathes.co.uk/myford-ml7/

Edited By Ady1 on 17/09/2012 11:56:21

James

It might be worth having a quick check in the hole that you took the grub screw out of, to see if there is a second grub screw below it, a trick used to lock the lower screw in place.

Otherwise I second Ady's advice about waiting for news from someone familiar with this machine.

Keith

Thanks for all the advice Chaps.

Pierre - thanks for that link to the explanation of the backgear. It makes it very clear.

Ady1 & Keith - I've carefully checked and there is no second grub-screw. There is also no means of lubrication as there is no provision for an oil nipple. The pulley is well and truly seized onto the spindle.

I hope someone familiar with this lathe can offer some more advice as I really stuck now.

James

Might be worth heating the assembly if it's gummed up or worse still, threadlocked together by a previous vandal owner.

As you suspect, this can only be a bodge. However, the clearance between the mandrel and the pulley bush is quite small. After a long back-gear operation on my Super 7 (facing with a fly-cutter), I sensed that the pulley was picking up on the mandrel. Perhaps I had the V belt a tad tight, so it was putting a lateral load on the pulley. Stripping out the mandrel revealed the slightest sign of pick-up in the bush, which was soon corrected with a bearing scraper. I resolved after that, always to make sure that it is all well lubricated when back gear is engaged. Perhaps a previous owner of your lathe experienced something similar and decided to make sure that all was locked up solid!

My worry is that the superfluous grub screw has raised a burr on the mandrel which will drag its way through the pulley bush as it is removed. It's probably too difficult to see down to the bottom of the hole. I was going to suggest the gentle application of heat but, of course you cannot remove the mandrel from the lathe with the pulley seized on. Mine wasn't that tight, but it still took a bit of more than gentle persuasion to drive the mandrel out through the pulley. I think that you will have to bite the bullet and drive it through, accepting that the bush may well be scored. It's either a new bush or plenty of work with the bearing scraper. Sorry about that.

Geoff

You can buy a replacement bush, which is a standard oilite size. You can (or at least could with Old Myford) buy a replacement bronze bush/gear, both are easy to press out and in.

My 1949 ML7 also has the same grubscrew assembly you remove that to oil the spindle when using the backgear.

If the machine has had a lot of use in backgear the pulleys wear internally they then make a rattling noise on the spindle that then leads to people tightening the screw all the way in so it contacts the shaft and locks the pulleys to the spindle eliminating the vibration & noise.

Sounds like your pulley is well and truly siezed, unless the machine has been thoroughly soaked and it's corrosion which I would doubt it is probably gummed oil causing it to stick, I would try using some thinners to break it down if that dosent work then some gentle heat but take care as the pulleys dont seem to be aluminium but some kind of mazak.

Paul

Paul - that seems to be the answer to the question of the grubscrew. Thanks for solving that. I'll now get going with penetrating oil/thinners. I'll bear in mind your warning about the material that the pully is made of.

James

My large Taiwanese lathe siezed up on me one day when I was working in backgear, not that long after I got it. The hand book failed to indecate how to oil the spindle. The bearing and spindle was OK, and I found that at the bottom of the V of two of the pullies (belthead) were grub screws, one holds the bearing, the other is the oil hole, you remove this, oil and put it back, been OK for well over 20 yrs. Ian S C