ML7 cross slide backlash

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ML7 cross slide backlash

This topic has 16 replies, 8 voices, and was last updated 20 February 2019 at 23:39 by Hopper.

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19 February 2019 at 19:48 #397054
AJW
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@ajw
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
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19 February 2019 at 19:48 #13434
AJW
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@ajw
19 February 2019 at 23:17 #397078
Chris Trice
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@christrice43267
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.
19 February 2019 at 23:34 #397079
Hopper
Participant
@hopper
That's good indeed. There's a reason these antiques still have a following.
20 February 2019 at 09:39 #397121
AJW
Participant
@ajw
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
20 February 2019 at 11:28 #397144
Wout Moerman 1
Participant
@woutmoerman1
Posted by Chris Trice on 19/02/2019 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.

What made the lead screws different in dimensions? Also heat treatment after thread cutting?
20 February 2019 at 12:13 #397155
AJW
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@ajw
Not sure how the die cast (mazak?) type material for the nut would be heat treated?

Alan
20 February 2019 at 12:45 #397157
Michael Gilligan
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@michaelgilligan61133
Posted by AJW on 20/02/2019 12:13:04:

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

.

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.
20 February 2019 at 13:16 #397161
Chris Trice
Participant
@christrice43267
It was on the old Myford Nottingham website that stated because of this issue, they would only supply feedscrews and nuts as a pair.
20 February 2019 at 13:47 #397169
Bazyle
Participant
@bazyle
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.
20 February 2019 at 15:23 #397187
Chris Trice
Participant
@christrice43267
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".
20 February 2019 at 15:52 #397191
ega
Participant
@ega
Posted by Chris Trice on 20/02/2019 15:23:05:

… "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!
20 February 2019 at 16:43 #397196
Chris Trice
Participant
@christrice43267
I took mine off about four years ago and put on the lever feed. Mine hasn't been back on since then either.
20 February 2019 at 17:52 #397210
Michael Gilligan
Participant
@michaelgilligan61133
Posted by Chris Trice on 20/02/2019 15:23:05:

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

[ … ]

.

Thanks for the clarification, Chris … That makes sense

MichaelG.

[ ML7R, with no such luxury ]
20 February 2019 at 19:24 #397217
Jon Lawes
Participant
@jonlawes51698
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.
20 February 2019 at 19:32 #397220
Chris Trice
Participant
@christrice43267
Posted by Jon Lawes on 20/02/2019 19:24:32:

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.
20 February 2019 at 23:39 #397259
Hopper
Participant
@hopper
Heat treatment for a Mazak nut? Probably straight out of the die and into a bucket of water.
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