Myford Super 7 cross slide

[silverfox]

I have just 'discovered' a bit of play in the cross slide
When i grip it and move it tp and fro i have 0.008 play

It isnt the adjustment collar but in the thread where it enters the slide itself

Would it be prudent to get an new feedscrew and nut supplied together and include the power feed nut as well?

Or is there a cheaper way?

[simplyloco]

Jun 18, 2019 20:27:09 GMT silverfox said:

I have just 'discovered' a bit of play in the cross slide
When i grip it and move it tp and fro i have 0.008 play

It isnt the adjustment collar but in the thread where it enters the slide itself

Would it be prudent to get an new feedscrew and nut supplied together and include the power feed nut as well?

Or is there a cheaper way?

Sounds like backlash to me, which just about all slides suffer from to a greater or lesser degree.  Your new DRO will take care of that for you. 
Do not worry...
John

[silverfox]

John

I would agree, but should i be taking a cut along an axle, it has the possibility of jumping back 0.008 or even forward !!( i was taking the readings off the DRO!)

I will have another look when i get back from the Hospital, but it isn't the free movement visible on the indicator wheel, which doesn't alter one micron when i move the slide.
If the replacement comes as a pair then there shouldn't be any play between the nut and thread. It is 50yrs old!! On the bright side it may be that the screws holding the nut onto the cross slide are a bit loose.

Ron

[uuu]

It shouldn't jump back, if you're applying depth of cut in the forward direction. But it can certainly get pulled forward into the work, particularly if you're cutting brass using a tool with top rake.

A replacement would still have some free movement, so you'd be better to develop a technique to deal with it, such as tightening the gibs a little to resist a pull forwards.

Wilf

[goldstar31]

8 thous is a lot of wear on a Myford Chinese metal nut. I doubt that the feedscrew will be badly worn but a new nut is fairly inexpensive.

I carefully- VERY carefully squeezed the offending nut to great effect but really it is time to consider at least a bronze nut.

I recall that Geo Thomas in the Model Engineers Workshop Manual produced a drawing of a bronze one. Saving desigbing one's own version but having to get the good book!

Of course, the Chinese in their SiegC4 have adjustable bronze nuts which should improve some peoples' views on their present machinery.

Rather intersting to be able to compare a Super7B, a ML10 and a C4 with a vertical drill/mill attachment.

[jem]

there is a youtube somewhere of a chap making a leadscrew nut in a plastic materiel, he molded it onto his leadscrew, and he claimed that it had no backlash and worked perfectly, maybe you could have a look for that video, as it did seem a very plausible way forward.

best wishes jem

[goldstar31]

Jun 19, 2019 16:41:11 GMT jem said:

there is a youtube somewhere of a chap making a leadscrew nut in a plastic materiel, he molded it onto his leadscrew, and he claimed that it had no backlash and worked perfectly, maybe you could have a look for that video, as it did seem a very plausible way forward.

best wishes jem

I've no idea about watching you tubes or whatever but my old lathe has been overhauled but the worn parts have been built up with 'filled plastic'. My worn Myford saddle was built up with Turcite and I'm aware that things like Moglice can build up other wear.

Wellm we don't know quite what these trade products are but it is fairly safe to think that they are all a setting plastic such as an epoxy resin and the filler is a hardwearing and sippery thing. The guesses are things like powered graphite, metal like bronze and so on as an alternative to softer things like powdered chalk, slate dust, sawdust and aluminium powder.

The days are long past since most of an old generation wear a part down to fit and instead we build worn things up instead.

Seemingly for many of us, we refuse to accept that plastics are a possible way out of mproblems.

Norman

[twombo]

Just a thought. 2 areas. Cause play in the cross slide, sloppiness in the screw and nut, and excessive wear in the thrust surfaces of the dial assembly. Both can be checked on a disassembled machine.

My Knowledge of Myfords is only very general. I would love to get my hands on one!

With the. Crossfeed screw and dial assembly removed from the cross slide, however you, push pull, or apply pressure. you should not be able to ‘open a gap’ between the fixed, and, rotating Parts of the dial assembly.

you should find a nice close fit in the works. 1 thou would be fine. With resettable dials. There is an extra area for looseness to develop.

I have recently gone through this process on my ancient south Bend lathe. You are all so fortunate to have George Thomas’s great thoughts and writings to draw upon. Tally Ho! And on with the hunt!

I would only add one bit. I write this with the presumption that the adjustable gib surfaces in the. Cross slide and Saddle assembly are properly adjusted.

ah, If I only had a myford to take apart and reassemble, it would be so fun to see what ‘ makes it tick’! The only thing that stops me is the difficulty of converting one to. 117 volt 60 hz power. The myford and it’s ecosystem s loaded with capablities, just Made to order for ME Pursuits!

Cheers!

[goldstar31]

Actually, many of the great thoughts actually come from Geo Thomas's friend Jack Radford of New Zealand and in the UK, a writer called Martin Cleeve. Both discuss the Narrow Guide System and its wear to a point where the inner guide- aye the inner guide becomes worn until it becomes convex. One can dispense with the use of the inner gib and bear the saddle on the number one shear and the number4. This was neverintended to be a bearing surface and surprisingly will be found on earlier models- quite unworn.

Not quite as is surmised

Cheers

Norman

[twombo]

Thank You Norman, for the Clarification! I really MUST have one of these things to play with!


Mick

[JonL]

I don't know how relevant this is but I modified my Myford ML7 with needle roller bearings for on the cross slide and dropped the backlash considerably.

www.arceurotrade.co.uk/projects/MYF001/myford-cstb-mod.html

It was like this but I sourced the bearings myself for a fraction of the price. I realise yours is a Super 7.

[92220]

One way of removing backlash from the cross-slide leadscrew is to accept the loss of something under 1/2" of travel, and shorten a second leadscrew nut to just a couple of threads and fit it, reversed, on the leadscrew, on the outside. With slightly larger fixing holes, it can be rotated until there is no backlash and then finally tightened. I may not have described this very well, but think of 2 nuts on a thread, tightened together....no backlash. Having a two piece leadscrew nut, was a method of removing backlash in some industrial machines, back in the 1950s/1960s. This is something I've been thinking of doing, for some time. Just haven't got around to it.

Bob.

[simplyloco]

My Emco Maximat V10P cross slide has a grubscrew in it which expands the nut to totally eliminate backlash. Beats me why it's not a standard fitting on every lathe, especially sacred ones...
John

[92220]

Hi John.

Same principal as I was trying to describe above. Yours just pulls the threads apart and mine pulls them together. Yes it does work well and I'm also surprised it's not used more often too.

Bob.