Myford ML7 Chucks - Which one?

Mine came with a 4" Griptru, which is worth seeking out if you can find a good used one at the right price.

Re locking the spindle, I've not used this method as I have a S7 with spindle lock, but Mr Jordan's method looks nice and easy.
Previous mention of a C spanner was to turn the chuck, rather than lock the spindle wasn't it?

Bill

I have a 4" chuck, but in the main I prefer the PB 5" chuck for general work. I consider the statement that a 5" chuck is too heavy for an ML7, to be utter tosh. My bearings are still in great condition, although I must admit to scraping them in about 30 years ago

Andrew.

It's much better to hold a stub of large hex in the chuck then use the spanner - over time, constantly doing it your way will stress the jaws/guides eventually, however slight the torque required. Personally though, I always use the chuck key to provide leverage

Engaging back gear and or inserting a piece of hardwood between the mesh is about the only way of locking the spindle on an ML7 if I recall correctly. As said the S7 has that very convenient locking pin.

Something you may want to consider - a few years back I bought a TOS self centering 4 jaw chuck the aim being to use it primarly for square section (obviously) but without the need to clock an independent in. Prior to this my main chuck of use was a Myford/Pratt Burnerd precision scroll 3 jaw bought with an ML7 around 1974. I kept this chuck when selling the lathe on and still use it today however it now takes second place, virtually permanently set up with soft jaws, in favour of the TOS four jaw. Constantly in use now it's a brilliant chuck - accurate (enough) and will do all the other one will. Wouldn't be without it now for sure and would uy another in favour of a sc 3jaw without hesitation - just a shame you can't get one with a Myford internal thread.

With regards to the 5inch - bought one of those about four or five years ago. Concerned about the overhang/weight with a conventional backplate I took it apart and found that I could machine the backplate in reverse and fit it to give a mounting same as a Myford chuck. I use only when neccesary - it doesn't 'appear' to stress anything but it does 'look' like it is.

Regards - Ramon

Edited By Ramon Wilson on 10/11/2020 22:28:18

Thanks all.

I refer to L. H. Sparrey’s book quite a lot, and he suggests locking the spindle by engaging backgear, then putting some brass bar between the chuck jaws and levering it undone. Using a spanner isn’t that different - probably less damaging than a bar if I’ve assumed the contact points and load paths correctly. So I use a combination of Sparrey’s method and the one in Peak4’s video). Can’t see any harm in it tbh.

The 5” chuck being too heavy may well be “tosh”, but it’s not my statement. I read through the thread that M.G. linked too, and the only certain thing is that nobody really seems to know if it overloads ML7 bearings or not. I have no particular desire or need for a 125mm chuck over a 100mm one, so there seems little point in going against the supplier’s recommendation. I’ll just have to wait until they’re in stock, or get an alternative such as Ramon’s suggestion.

Ramon - you said the self-centering 4 jaw chuck was in constant use; what do you use for non symmetrical parts? Does it work independently as well somehow, or did you mean you’ve got another independent chuck?

Thanks all.

Edited By Dr_GMJN on 10/11/2020 23:10:38

If you get a new Chuck go for a 4 jaw self cantering. They give a very solid grip on material are incredibly accurate and contrary to popular belief they still grip hex material on centre. Despite the warnings above, my 125 mm has been on my well used S7 for 20 years with no ill effects

GandM Tools have a tidy used 100mm TOS with both sets jaws etc. already on a Myford backplate listed at the moment - I have one, it's a solid and dependable chuck..

Edited By DiogenesII on 11/11/2020 06:32:23

Doc G, I have two independent chucks a 4" and a 6" the latter with Myford internal fitting so use those for irregular shapes.

As said I bought the SC 4 jaw thinking it would be handy not to have to clock square stuff in when using those - ust pop it in the chuck and get going. I use it for round most of the time now but of course it does square and hexagon when required. No, it does not work independently - another SC chuck but more versatile. Recommended!

Ramon

PS If you go this route you could fit your existing 3 jaw with soft jaws and have more versatility - something else I use constantly throughout a build - very useful.

Edited By Ramon Wilson on 11/11/2020 08:23:41

Thanks all.

Just noticed Arc do a Self-branded 100mm s/c 4 jaw chuck “Chinese Origin”. Anyone got experience of them? At least it looks nicely finished.

I have an HBM one which seems nicely finished and is pretty accurate; currently mounted on my dividing head.
I'm sure Ketan would give you an honest opinion on the ones he's selling, particularly as he is changing supplier by the looks of it.

I seem to recall him writing about it in past thread somewhere.

Bill

The number of broken teeth on ML7 back gears would suggest that they are fragile and it’s not a good idea to lock the spindle with this method. Usually a chuck will unscrew with not too much force required and the back gear will be untroubled but if a heavy interrupted cut has be used the chuck can be difficult to remove. Spinning the chuck on with enthusiasm can make it very tight. If the chuck is anything other than easy to remove then think again about how to lock or hold the spindle. Sparey was a very skilled engineer and most likely had a well developed sense of mechanical sympathy so wouldn’t employ a bigger hammer or longer lever if his chuck was stuck.

Mike

Interesting suggestion and I didn't know about the hex point.

I can't help feeling that a 4J SC would have to have exceptional accuracy for each jaw to bear equally on round stock. I have got one which I use for non-critical holding of cold-rolled square bar but for accuracy and grip would use the independent 4J.

For my admittedly larger chucks on my larger lathe, a hole was drilled into the chuck body. Into this is inserted a bar with a short matching piece of Silver Steel attached to it. With the belt tight, a swift blow on the end of the bar with a copper / hide mallet slackens the chuck.

To avoid risking the gear teeth, you could grip a piece of relatively large hexagon bar in the 3 jaw, ( Square for the 4 Jaw ) and apply a long spanner to the metal before using a copper / hide mallet on the outer end. The inertia of the motor and the Headstock usually provides enough resistance to a sudden blow, to slacken the chuck ..

If at first you don't succeed, give it another whack, and do follow through!

Remember the advice, not to run the chuck on under power. They will be quite tight enough, possibly more so, if just spun on by hand!

To reduce risk of chucks sticking, the threads and register on the Mandrel and in the chuck should be clean. Mine given a wipe, or brush, every time before fitting, (Ditto when changing from Internal to External chuck jaws. )

HTH

Howard

I might have given the wrong impression somewhere, but I’ve never had an issue with the unscrewing a chuck. I’m doing light work, and certainly don’t over-tighten them. If I thought I was going to have to apply a hammer to the spanner, or extend its handle, there’s no way I’d be using the gears to lock it. Remember the gears themselves aren’t made of cheese - they can handle some torque...I’d expect way more than I ever apply on chuck removal.

A friend with a Myford used to loosen the chuck with backgear engaged. I cut several replacement gears for him.

Glad when he sold the lathe.

A suddenly applied force has double the effect of a gradually applied one. So using a mallet on a spanner against the inertia of the machine, rather than locking the gears, does no real harm. It will slacken many a "stuck" chuck without doing damage. All that may happen is that the Mandrel may rotate slightly.

The "Mallet on a 12 inch lever on an unrestrained Mandrel" works on my 8" chuck (At least four times the inertia of a four inch chuck  ) so should have no problem with a four inch one!

Chucks do self tighten. As the work heats up, the chuck body eventually warms and expands and cutting forces screw the chuck a little further on. When cold the chuck contracts onto the mandrel, and will be tight to remove.

Howard

Edited By Howard Lewis on 12/11/2020 17:30:48

Howard, I'd expect a shock load applied to a chuck (via. a spanner on the jaws or an in-situ hexagon bar or whatever) might not damage the gears, but might not do the chuck any good?

As I said I'm not doing heavy work where I'm generating significant heat or load. I've never needed anything other than hand pressure on a large adjustable spanner to loosen them.

Doc, you are fortunate.

Most of the rest of us do find such problems from time to time. Hence the variety of solutions quoted.

The problem of sticking chucks will be present at some time for almost anyone with a screw on chuck.

may your good luck continue.

Howard

Can I point out that the chuck in question was a 4 JAW self centring chuck backplate mouted. I have one and it gets used for accasional use. Myford (Mytholmroyd) did warn against it as well as selling it. I asked them at a show what the thinking was and the response was it just looks too heavy for the lathe. The went on to add that they would not imagine any harm being done by occasional use. My interpretation was that the notice was a recommendation but came accross as a warniing notice instead.

4 jaw independent chucks of this diameter don't overhang nearly as much as this chuck and the same is true of screwed bodied chucks.

I appologise to anyone who has been through this conversation before but I thought it worth including this in this thread too.

regards Martin

Martin, the chuck in question that I’m talking about is a 3 jaw. It’s here:

**LINK**

If you can get hold of a used 100mm griptru 3 jaw it has a very accurate adjustability. I got one on the myford ,when purchased along with a 125mm 4 jaw independent. I say used because it looks like they are around £500 new.

Mine was running out nearly 9 thou & i just thought it was how a 3 jaw was. Until i saw a thread on here about them being adjustable. This is how accurate i got mine at the moment. Other makes i cannot comment on as this is all i have.

Steve.