Odd extra lever on Myford ML7 leadscrew drive

I just bought this 50s vintage ML7 and am by no means an expert in lathes or Myfords, but it appears to have somewhat of a non-standard feature.

If you look down in the far left, bottom corner of the photo, there is a chrome lever. I don't see this in the manual or in other pictures of ML7 lathes on the web.

It shifts one of the gears outwards, on its axle, so that it is no longer in mesh and disengages the feed to the leadscrew. But isn't this redundant, as the tumbler lever just above it on the back bearing of the headstock includes the same function in one of its three positions - forwards, disengage, reverse.

I bought the lathe without guards but have sourced some on ebay. The change gear guard looks like it will foul this lever if I fit it. Though, to be honest, I've only had a quick look so far and not actually dismantled any of the gears to try to fit the guard. So, maybe all will be well.

I wonder though if anyone has seen anything like this before or can offer a good explanation as to why this lever is present.

Thanks and regards,

Matt.

Matt

Certainly non-standard, and your lathe has some other owner modifications.

Would suggest that the chrome lever is to disengage the drive while "on the run" without stopping the motor. There might be a bit of a crunch when re-engaged, but the leadscrew is only rotating comparatively slowly.

The headstock levers should only be used when the lathe is stationary.

Matt,

It will probably be a method of reproducing the effect of a leadscrew clutch. Turning the leadscrew by hand with the tumbler lever in neutral is extremely difficult, especially if you have a gear train setup for very fine feed.

Jim.

Edited By Jim Guthrie on 16/09/2016 08:28:07

Matt,

Forgot the words I needed above, but this will act as a "dog clutch" as used on the leadscrew of several small lathes

Got pics of the working end of teh lever and the gear it moves in more detail? It may be some form of dog clutch, in which case it is a really, really handy thing to have for screwcutting. The authoritative book on dog clutches for Myfrods is probably "Screwcutting in the Lathe" by Martin Cleeve. Still in print as part of the Workshop Practice series of books.

Thanks chaps.

I should take some photos of the business end when I get the chance. It is still on a trolley on the workshop floor.

Not a dog clutch though, it is regular gears so it might crunch a bit operating it on the fly. Maybe not so bad given the slow speeds. It makes sense that it will make the manual leadscrew wheel much easier to turn without as many gears attached as you would have using the headstock lever.

A friend had a look last night and suggested it was a "production line" modification, like the lever tailstock. Though, as far as I know, the (one) previous owner was a hobbyist. It's been in a self-built garden shed since 1950. He could still have been doing repetetive runs of things though.

There's an odd extension on the cross slide and I knew from the start that the topslide and tool post was missing. It looks like the last few things to be turned on the machine were wood, using the rear toolpost.

If used as a dog clutch for screwcutting it must be a single dog or else the thread would not pick up correctly. OP says it merely slides a gear, the standard lever on the apron would be a better primary event.

Not a dog, not single.

There is a gauge/pointer on the right hand side of the apron (you can just see it in the fuzzy phone photo). This might allow engaging the leadscrew in correct sync if you can eyeball it against the thread - with some practice! - but that would be using the apron lever, not the additional lever I think.

Some photos of the extra lever. It moves the bottom middle front gear in and out on its axle.

Yes it looks like it disconnects the fine feed gear train so the leadscrew can be turned by hand usin gthe handwheel at the right hand end of the lathe bed. Probably not intended to be engaged when the gears a whizzing around as it could chip teeth etc, but very handy nontheless.

I fitted a similar lever to my mini lathe.

It is really handy to be able to quickly move the leadscrew in and out of engagement rather than fiddling with the less accessible tumbler reverse with the ever-present risk of engaging the wrong direction.

It's also a positive disengagement, unlike the half-nut lever that is too easily knocked into engagement by accident.

Neil

Thanks Hopper and Neil.