ML7 cross slide backlash

I have just fitted the Arc Euro needle thrust bearings and ball race to my ML7 cross slide machining the end casting as prescribed.

All went together nicely, gave the thrust bearings a slight pre load and all feels good.

I have measured the endfloat on the cross slide which shows I have 0.003 in of wear in the leadscrew/nut assembly, I thought that wasn't too bad?

I fitted a new long cross slide and feed screw probably 30 years ago but the nut is original from 1951!

Alan

I did a similar conversion a few years ago on my Super 7 and got similar results. Talking to a Myford bod at the Nottingham factory at the time, I was told that the nuts were heat treated which often changed their dimensions so they were matched to specific feedscrews as pairs to keep backlash to a minimum. .003" was considered an excellent pairing.

That's good indeed. There's a reason these antiques still have a following.

That's great then! I thought I might have had .003 of wear in the nut/leadscrew, but if they could have been like that from new! I was considering a new nut to try and reduce the clearance.

I always keep the cross and compound screws/slides well lubed my favourite being Castrol graphite grease I guess it has paid off over the years.

So far I can recommend the thrust bearing mod it makes for a different 'feel' but in a good way.

Alan

What made the lead screws different in dimensions? Also heat treatment after thread cutting?

Not sure how the die cast (mazak?) type material for the nut would be heat treated?

Alan

.

By melting it, to produce a die casting

But seriously [unless the story was pure hype], I suppose that 'controlled cooling' could qualify as 'heat treatment'

MichaelG.

It was on the old Myford Nottingham website that stated because of this issue, they would only supply feedscrews and nuts as a pair.

Is it just Mazak or is it white metal bearing composition which would be a logical quality alternative to bronze? I'm dubious about heat treatment and might just have been an excuse they hoped would be sufficient to bamboozle most people.

Going through some of my Myford paperwork, I found this relating to the power cross slide feednut which is where I think some confusion lies and where my memory comes from as I have a power cross feed Super 7: " During the hardening process of the cross slide feednut, the thread in the feednut tends to close up. Accordingly each feedscrew is finally finished in terms of size to fit an individual feednut. Therefore, replacement feednuts are not available as an individual item as most likely they will not be a good fit, and in some cases they will not fit at all. To ensure the best possible outcome the power cross slide feedscrew and nut is only available as an assembly.... Replacement feednuts are not available as single items".

In respect of the other feedscrews, no reference is made to heat treatment so I concede that point but they were also only available (and still are) as a matched pair : "Note: To ensure the best possible outcome when replacing worn feedscrews, replacement feedscrews are only available as an assembly fitted with a feednut".

Slightly OT but his reminds me of buying a replacement triple start feednut for the S7 tailstock which the existing feed screw simply would not enter. As a temporary measure I fitted a lever feed; that was years ago and I have never missed the standard arrangement - one of life's rare blessings in disguise!

I took mine off about four years ago and put on the lever feed. Mine hasn't been back on since then either.

.

Thanks for the clarification, Chris ... That makes sense

MichaelG.

[ ML7R, with no such luxury ]

I did something similar on my ML7 I suspect, I bored out the hole that the shaft goes into and fitted a 1/4 x 3/8 x 1/8 sealed bearing, with an NTA411 bearing either side (a needle roller bearing with washers, two of, part number NTA411).

The reduction in free play was very noticeable, especially after a further adjustment later on when they had all bedded in.

Me too on my Super 7 and it's another of those mods I never regretted doing. The feel is so much better.

Heat treatment for a Mazak nut? Probably straight out of the die and into a bucket of water.