Evaluating & Correcting Wear in an ML7

[Dr_GMJNParticipant @dr_gmjn]

[Dr_GMJNParticipant @dr_gmjn]

All,

I bought my ML7 about 13 years ago, and did a light refurb on it (basically stripped, cleaned and painted):

I've only really started to use it properly this year, for building a Stuart 10V.

It works fine overall, but there are some foibles, such as the cross slide dials are stiff and aren't re-settable, and the saddle stiffens up at each end of its travel, with a free spot about 1/3 of the way back from the chuck (as is common on old lathes I suppose). I've adjusted it to allow me to work in the region of the ways that most often get used, but on the occasions I need full travel, if just feels too stiff, and is just not very nice to use. A few questions:

1) How do I determine the amount of wear I've got in the ways?

2) Is there any way to compensate of the variable wear, or is it a re-grind?

3) How much wear (as measured in 1) makes a re-grind impossible?

4) Where, and how much would it cost to re-grind and re-fit the saddle?

I'm just after preliminary info at the moment, so I can make a decision on whether to put up with it, or get it done. I am planning more steam engine builds in future, but I'd like to get the lathe sorted out first.

Thanks.

[Dave WoottonParticipant @davewootton]

Hi

There have been some excellent articles in recent issues of Model Engineers Workshop on this very subject written by Peter Barker they would probably cover all your needs for checking and improving your lathe without the need for a regrind.

Resettable dials for cross and topslide are still available from Myford, or there are drawings in Geo Thomas's book, well worth buying anyway, if you feel like making them. I'm afraid I was lazy and bought the Myford ones for my ML7R and very nice they are too.

There is also a free drawing of a needle roller thrust conversion on the Arc website, not done it yet but been told it's worthwhile.

I think Peter Barker might be Hopper on this very forum.

hope this is useful

Dave

 

Edited By Dave Wootton on 22/09/2020 15:17:47

[Dr_GMJNParticipant @dr_gmjn]

Posted by Dave Wootton on 22/09/2020 15:12:58:

Hi

There have been some excellent articles in recent issues of Model Engineers Workshop on this very subject written by Peter Barker they would probably cover all your needs for checking and improving your lathe without the need for a regrind.

Resettable dials for cross and topslide are still available from Myford, or there are drawings in Geo Thomas's book, well worth buying anyway, if you feel like making them. I'm afraid I was lazy and bought the Myford ones for my ML7R and very nice they are too.

There is also a free drawing of a needle roller thrust conversion on the Arc website, not done it yet but been told it's worthwhile.

I think Peter Barker might be Hopper on this very forum.

hope this is useful

Dave

Edited By Dave Wootton on 22/09/2020 15:17:47

Thanks Dave.

Do you happen to know what the dates of the relevant magazines were?

[KWILParticipant @kwil]

Dave,

You have a PM.

[Mark Cunliffe 3Participant @markcunliffe3]

Hi Dave

The needle roller thrust bearing upgrade, is that for the headstock?

Can you share a link, sounds like something I'd be interested in. Thanks

Mark

[Dave WoottonParticipant @davewootton]

Hi Mark

The needle roller conversion is for the crosslide feedscrew and only applies to ML7 and ML7R , it is on the projects section of the ARC Eurotrade website, they also sell the bearings required very cheaply.

I think there have been roller bearing conversions published for the Super 7 & ML7R headstocks, but I've never looked into it as I'm quite happy with mine as it is.

I'm not at home to check but I seem to remember the articles on Myfords by Peter Barker were around October 2019 to March 2020, well worth seeking out.

KWIL I had a look but I can't find a PM from you.

Dave

 

 

Edited By Dave Wootton on 23/09/2020 10:50:17

[HopperParticipant @hopper]

Hi Dr GMJN

My articles on refurbishing the ML7 appeared in the following issues of MEW: 285, 287 , 289, 290 and 292. The first one outlines measuring the bed for excessive wear.

In a nutshell, Myford's literature recommends a regrind if wear on the bed exceeds 5 thou in the vertical plane and 3 thou in the horizontal plane. The first is measured with a micrometer on the vertical thickness of the front shear i the wear area, compared with the relatively unworn tailstock end of the bed. But most critical is the horizontal measurement. On a pre-1972 "Narrow Guide" model, you measure the width of the front shear with a micrometer and compare the worn area with the tailstock end. Or on a post-1972 Wide Guide model, you meausre across the outside from the front of the front shear to the back of the back shear.

If yours is a Narrow Guide model, the easy fix is my simplified Wide Guide conversion in issue 285. This is an easier version than both the original Radford method and the later one from the 1970s by.Richard Ganderton. My method does not require a milling machine. It can be done with hand tools and maybe a drill press if you have one.

The other articles in my series include using a vertical slide to get the lathe to manually machine its own inner shear faces to guide the tailstock and scraping the headstock bearings and setting the tailsotck alignment.

Have fun.

Pete Barker

Edited By Hopper on 23/09/2020 10:51:09

Edited By Hopper on 23/09/2020 11:10:22

[Dave WoottonParticipant @davewootton]

Hi Peter

Thanks for that, I just re-read the messages and I think there is some confusion crept in, it's not Dave (me) that wanted the dates but the OP who is Dr-GMJN. Fortunately my lathe doesn't yet need any major work, but I have filed all your articles away in case I live long enough to wear it out!

Great articles by the way, well thought out and presented.

Dave

[KWILParticipant @kwil]

Dave Wooton, sorry wrong Dave!!

I detailed about Roller bearing conversion of Super 7 in MEW some time ago.

[HopperParticipant @hopper]

Thanks Dave. Duly noted and corrected. Glad you liked the articles. I must get around the writing the final installment on final setting up on the bench and alignment etc. Life keeps getting in the way…

KWIL, the roller bearing conversion is something I would love to do to my ML7. Pet peeve is all that oil dripping everywhere from the plain bearings and oilers. (Reminds me of my bloody old Norton). What issue was your conversion article published in?

[Dr_GMJNParticipant @dr_gmjn]

Thanks everyone. I'll re-measure the ways at lunchtime. BTW IIRC my lathe was built in 1957.

I will try to get hold of all the articles as back issues.

Hopefully I can improve the feel of it without a regrind. I think it's always nice to have something 'perfect', but the real question is "how perfect does it have to be for the work I'm doing?" Obviously cost has to be factored in as well.

I'm really enjoying building the 10V, and all being well it won't be the last engine I build. The other factor therefore is the time spent trying to fettle it so it's as good as it can be (something I'm always fiddling with) vs. time spent turning parts and wondering what proportion of dimensional error is my fault (probably all of it to be honest).

[HopperParticipant @hopper]

Hi Doc

If its a 1957 you are in luck — its a Narrow Guide so doing the Wide Guide conversion will most likely fix your binding at the ends of the bed problem. I think you can buy individual digital copies online at Magzter or something like that, but not sure because I get the paper copies myself.

Yes, the restoration of old machine tools can become a hobby in itself…

And the making of model engines becomes an exercise to prove the capabilities of the restored machine…

Edited By Hopper on 23/09/2020 11:56:26

[Dr_GMJNParticipant @dr_gmjn]

So I just found the aforementioned article by "R. A. Ganderton" on correcting wear on these lathes. From what I can make out, in simple terms he suggests milling back the short face of the saddle – the bit that apparently wears the most and causes the corresponding wear on the front slide – to give a clearance fit. You then use the rear face of the rear slide as the bearing instead?

Is that basically what the method is? If so I will go ahead and get the back issues and have a go – especially since the method outlined in there is simplified?

Are there any issues with subsequent alignment of the leadscrew split nut, or is it adjustable?

I do have an SX2P Mill, so I guess any machining could be done on that?

Cheers.

[Dr_GMJNParticipant @dr_gmjn]

Posted by Hopper on 23/09/2020 10:49:32:

If yours is a Narrow Guide model, the easy fix is my simplified Wide Guide conversion in issue 285.

Pete Barker

Thanks Pete,

I looked at the covers of back issues – is it 285 or 287 where the wide guide conversion is outlined?

Cheers.

[KWILParticipant @kwil]

Hopper,

Roller bearings, Myford Super 7 NOT ML7.

[HopperParticipant @hopper]

287 is the wide guide issue. 289 is planing the inner shears to hold the tailstock true. 285 is measuring the bed.

I went the other way from Ganderton and attached a strip of thin gauge plate to the saddle to bear on that rear shear surface. I then machined a little off the leadscrew brackets to move it rearward by the same amount as the saddle moved.

[Dr_GMJNParticipant @dr_gmjn]

I bought the back issues online and printed the relevant bits out:

I'll re-measure the ways (although I know they are worn), and get on with the modification once the 10V is finished.

Ganderton seemed to say (and I may well have mis-interpreted his method) that the apron could, without modification, be moved back enough to compensate for using the rear of the saddle without adding a strip. If so, it seems like milling the short saddle bearing is a much easier way to do the modification. Even if the leadscrew bearings do need milling, you've still avoided having to dowel a strip to the saddle.

I think the gap quoted is 0.035", so why not combine the two methods and pin a 0.035" strip to the rear saddle bearing, relieve the short saddle bearing to give clearance, and avoid modifying the brackets altogether; is a 0.035" thick strip too flexible to attach reliably?

I'm no expert on lathes, so I'm curious to know what the relative advantages/disadvantaes of the two methods are? Have I missed something in terms of accuracy in terms of what the various methods will give?

Cheers.

[HopperParticipant @hopper]

The gap varies from lathe to lathe. The strip you add needs to be slightly larger than the gap so the old narrow guide surface is no longer in contact with the bed.

Unless you use the Ganderton method and mill that surface away. But your saddle will then move forward until the rear surfaces contact. Unless you add a strip of approximately the same size as the original gap. But gauge plate comes in 1/32" increments so its a maybe.

[Dr_GMJNParticipant @dr_gmjn]

Posted by Hopper on 28/09/2020 22:42:07:

The gap varies from lathe to lathe. The strip you add needs to be slightly larger than the gap so the old narrow guide surface is no longer in contact with the bed.

Unless you use the Ganderton method and mill that surface away. But your saddle will then move forward until the rear surfaces contact. Unless you add a strip of approximately the same size as the original gap. But gauge plate comes in 1/32" increments so its a maybe.

OK thanks.

I just measured the gap, and it's consistently 0.022" all along the bed and at each end of the saddle.

Shim Steel seems to be available in that thickness, with a +/- 0.001" thickness tolerance.

Could a strip be bonded to the rear face of the saddle, compressed by the gib strips until it set? I guess it could be scored, bent and screwed around each end of the saddle ends as a backup fixing, and the lower kepper plate would prevent it from falling out? Might cause some bowing at the ends though.

I wonder if going to 0.025" shim would allow the saddle to move out of contact with the short bearing, and compensate with the gib strip. I'd have thought the leadscrew half nut could cope with a 0.003" misalignment – or the apron could easily be moved by that amount?

Is that a total bodge, or is it viable? Guess there's not much to lose by trying, assuming I'm comitted to converting to the wide-guide concept anyway.

[HopperParticipant @hopper]

I suppose you could glue a piece of 25 thou shim on there but it would be kind of flimsy. And the very small gap on the old narrow guide could jam up with swarf. I'd prefer some 1/16 gauge plate or maybe at least 1/32 myself. But you could give it a try and see how it goes.

If you were to use 1/32" gauge plate or ground stock you might get away with just enlarging the apron mounting bolt holes to get apron alignment back in spec.

[Dr_GMJNParticipant @dr_gmjn]

Posted by Hopper on 29/09/2020 12:32:31:

I suppose you could glue a piece of 25 thou shim on there but it would be kind of flimsy. And the very small gap on the old narrow guide could jam up with swarf. I'd prefer some 1/16 gauge plate or maybe at least 1/32 myself. But you could give it a try and see how it goes.

If you were to use 1/32" gauge plate or ground stock you might get away with just enlarging the apron mounting bolt holes to get apron alignment back in spec.

OK great, I'll think about it some more.

I was just thinking that in your article, you Loctited your 1/32" strip (and of course dowelled it). I know that good bonded joint design means putting the joint primarily in shear, which of course this would be exclusively. Quite a large surface area too, and it's always clamped. I'd say it ticks all the boxes for a purely bonded joint. Even so, "glue" just seems a bit of a short cut, even though that's not necessarily true.

Milling the short bearing isn't an issue for me if it needed some more clearance, it was avoiding machining the leadscrew bearing housings if at all possible that I wanted.

Cheers.

[HopperParticipant @hopper]

I used 1/16 gauge plate. My gap was larger than yours though.

Machining the lead screw mounts was dead easy.

Or if you use the Ganderton method and machine away the narrow guide and use no strip , you could just put shims behind the leadscrew mounts.

[Dr_GMJNParticipant @dr_gmjn]

Posted by Hopper on 29/09/2020 13:02:35:

I used 1/16 gauge plate. My gap was larger than yours though.

Machining the lead screw mounts was dead easy.

Or if you use the Ganderton method and machine away the narrow guide and use no strip , you could just put shims behind the leadscrew mounts.

Yep, so many options I forgot that one. Use the 0.022" shim steel to make shims for the bearing blocks I guess.

[Dr_GMJNParticipant @dr_gmjn]

All, I finally got around to measuring the ML7 beds today, using some borrowed micrometers.

I noted the measurements as per Pete's article instructions.

Disclaimer: this is the first time I've done this, so I may have made incorrect assumptions!

So the first assumption is that the rear vertical face of the rear bed is totally unworn, ie straight left-to-right. This is my "reference" surface for overall widths and calculating other stuff.

The second assumption is that "wear" is the difference between the largest and smallest measurements of a particular area. Seems valid w.r.t. Myford's dimensions, compared with the least used bits of the beds.

Anyway, on the evidence of just the raw data, all the wear is within the stated limits for re-grinding, and – I'd hoped – for the wide-bed conversion…

I then put the data into a spreadsheet, and plotted graphs of the measurements at the 1" spaced 24 points along each bed. The individual graphs are here:

The scatter here is probably due to the tiny differences in width

I then calculated the gap width between the two beds. Seemed reasonable – more wear at the tailstock end from moving it backwards and forwards, but nothing massive:

I then plotted graphs that represent a plan view of the rear and front beds, with their actual width variations exaggerated, and this is what I got:

So, unless I've made an error somewhere, my lathe seems to be an anomaly according to Pete's article, becasue it seems to be the front of my front shear that's worn, not its rear. This appears to be confirmed because the overall bed width and front bed width graphs are pretty much the same shape. Anyway, it is what it is.

So the question is: in view of the fact that my lathe appears to have a uncommonly worn front vertical shear (no idea why, as far as I know it was only ever used for model engineering), is it even worth considering converting it to wide bed? I can't see it will make any difference if I've understood the method correctly?

So is the only option a re-grind, since it seems to be within limits for that?

Thanks all.

[Author]

Posts