Twist in an ML10 bed

This topic has 13 replies, 11 voices, and was last updated 29 August 2017 at 13:57 by Lambton.

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28 August 2017 at 19:45 #314329
Andrew Tinsley
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@andrewtinsley63637
I have been checking an ML10 lathe and using a sensitive level, it is apparent that there is some twisting occurring in the lathe bed.

The ML10 is mounted on the standard Myford stand. I have slackened off the securing bolts which holds the stand to the concrete floor. The twist is still apparent. Now if this were an ML7, then suitable adjustment of the jacking screws beneath the lathe would correct the twist. The ML10 seems to be simply bolted to the horizontal sheet steel of the stand, with no corrections available.

So do I start to eliminate the twist by using shim steel beneath the corner of the lathe which needs adjusting? Or am I missing something?

Andrew.
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28 August 2017 at 19:45 #8847
Andrew Tinsley
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@andrewtinsley63637
28 August 2017 at 21:10 #314343
vintagengineer
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@vintagengineer
Try un-bolting it from the stand and see if it is still twisted.
28 August 2017 at 21:41 #314347
Andrew Tinsley
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@andrewtinsley63637
I am not quite sure that it will do me any good. If it isn't twisted after unbolting it from the stand, I will need to shim up the offending corner. If it is still twisted after unbolting, I am still going to have to shim up a corner. It doesn't seem to get me anywhere! Assuming I am not missing something blindingly obvious!

I suppose my real question is, should I shim up the offending corner using ordinary shim stock, or is there a better way of correcting the twist, using some other method of jacking up the offending corner? Maybe using longer hold down bolts, upside down, using a nut to secure the bolt in place and then threading on another nut on which the bed rests. I could then use these nuts to give me a jacking effect. Obviously washers should be used too! The bed would finally be secured by a hold down nut and washer on the top of the lathe lugs. By carefully measuring the twist with the level, I could use the nuts under the bed as jacking nuts. Sounds a bit crude, but better than shim stock?

Andrew.
28 August 2017 at 22:33 #314350
Bazyle
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@bazyle
The trouble with nuts is that unless the thread is fine adjustment is difficult.
28 August 2017 at 22:33 #314351
Clive Hartland
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@clivehartland94829
Is the Metal Myford cabinet sitting on the concrete? Does it have cushion type anti vibration rubber feet fitted in the base of the cabinet? I would do that first which will even out any load tending to twist the cabinet and then the Lathe. My ML10 sits flat in all directions and positions along the bed and I did not tighten any bolt more than a snug up.

I cannot see an ML10 bed twisting as it is substantial and does not need any force to set up and mine has been sitting there for 17 years!

Clive
28 August 2017 at 22:51 #314353
duncan webster 1
Participant
@duncanwebster1
I would
1. unbolt the lathe from the cabinet
2. shim the cabinet to floor till it doesn't rock and is reasonably level
3. bolt cabinet to floor
4. then set up the lathe using shims under the feet if necessary
If you have a precision level use it, if not use 'Rollies dad's method' (Google it)
29 August 2017 at 06:28 #314366
Hopper
Participant
@hopper
Have you measured the bed on the ML10 to see how many thou of wear are on the top surfaces? And taken that into account when setting your levels?

Have you thought about not spending time trying to level a worn bed and instead cut to the chase and turn a test bar about 1" diameter by 6" long, held in the chuck with no tailstock centre. Adjust the feet with shims until it turns true.

As long as it turns true, why should you care if it's level?

Shim stock cut into a U shape and slide under the foot that needs raising should give adjust as good as or better than the adjusting screw raising blocks used on the ML7s in some cases. (Heed Duncan's advice about setting bench firmly on floor first.)
29 August 2017 at 07:38 #314373
not done it yet
Participant
@notdoneityet
KISS Principle – if the bed has twist in it it should be removed.

KISS Principle – shimming is the obvious choice and documented in (most?) manuals.

KISS Principle – start with the floor connections and work upwards. Absolutely no point in levelling the lathe before levelling the stand.
29 August 2017 at 08:07 #314378
Muzzer
Participant
@muzzer
It can only twist significantly if all 4 bolts are tightened down onto a (fairly) solid base such as an industrial stand (with a twist in it). So how about loosening off the 2 bolts holding the tailstock end? If it really does have a twist in it, that should significantly reduce it and you'll know where your problem is. I can't imagine you actually need the tailstock bolts to be torqued down firmly but you could then shim up any resulting gap if you insist.

Or to paraphrase – start from the top down.

Murray

Edited By Muzzer on 29/08/2017 08:07:50
29 August 2017 at 08:26 #314382
Michael Gilligan
Participant
@michaelgilligan61133
Excellent diagnosis, Murray

If it was mine, I would take the opportunity to convert the bed to three-point support

… a couple of spacers at the headstock end, and a bridge between the fixing points at the tailstock end [with a single support at its midpoint].

MichaelG.

Edited By Michael Gilligan on 29/08/2017 08:26:41
29 August 2017 at 09:58 #314390
Robbo
Participant
@robbo
Back to basics and the Myford instructions. (abbreviated)

Place cabinet with packings under the feet until the top is roughly level and the feet bear evenly on the floor. Coolant should run towards the plug'ole. Note "roughly level".

Next refers to mounting blocks. Shims should be used ……… so that the lathe bed is not twisted when fixing bolts are tightened down.
29 August 2017 at 10:16 #314394
Andrew Tinsley
Participant
@andrewtinsley63637
Thanks guys,

Interesting that some say start from top down and others from bottom up! I have bolted the cabinet down to the concrete floor with rawbolts and inserted some anti vibration material between the feet and floor. The cabinet was roughly levelled and a slope included from headstock to tailstock for coolant flow.

The lathe bed shows no measurable wear, so that isn't the problem! It also turns reasonably true, about 6 thou out in 10 inches. The twist isn't very much , but I may as well get it correct, rather than leave it (I suspect most people would be satisfied as is!).

The U shaped shims sound as if it is the way to go, so I will stop bothering you all and get that done! If I had not got a sensitive level, then I would have carried on in blissful ignorance. Having got one, I may as well use it to get things spot on.

Thanks all,

Andrew.
29 August 2017 at 13:57 #314421
Lambton
Participant
@lambton
Andrew,

"If I had not got a sensitive level, then I would have carried on in blissful ignorance."

How right you are. I once bought a very expensive Swiss precision level thinking this would be a great asset however it almost drove me mad as the bubble went off the scale so easily that it proved impossible to use the thing in the real world of a model engineer's workshop. So I got rid of the blasted thing and reverted to my old but trusted 6" Moore and Wright level.

Andrew, does your lathe turn parallel? if it does forget all about altering anything dust to get things "level"

Eric
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