Worn Myford

[David Clark 13Participant @davidclark13]

I think the saddle was gang milled. I may even have a photograph or two. I will look later.

Edited By David Clark 1 on 17/09/2015 16:19:44

[CotswoldsPhilParticipant @cotswoldsphil]

Posted by David Clark 1 on 17/09/2015 16:19:26:

I think the saddle was gang milled. I may even have a photograph or two. I will look later.

Edited By David Clark 1 on 17/09/2015 16:19:44

Thanks David.

Regards

Phil

[KWILParticipant @kwil]

If you follow this link you should find gang milling picture on page 3.

http://www.quillstar.co.uk/Follow a Myford Lathe Rebuild

[AjohnwParticipant @ajohnw51620]

The main reason the saddle wears so quickly is that the contact length on the rear of the front rail is rather small and things will twist a bit in use. The inner one can't be as long as the outers as these need to go past the tail stock to give a usable machine.

If they didn't do this the lathe would have the same "problem" as ML10's etc a rather narrow saddle compared with the width of the bed. That means for the same clearance needed for reasonably easy movement causes more rock than a lathe with a longer guide. The clearances have to be very low but the saddle will tend to twist / move under load. This is often a problem on lathes that use a dovetail on the bed and they can wear quickly as well.

This is an area where prismatic beds score heavily over others although the best arrangement isn't always used. The outer prisms ( ^ 's) can run all along the bed. The head and tail stocks sit on another prism which also aligns the head. 2 are used for this on larger high end machines as the tailstock gains the same advantage mentioned for the saddle shortly – cutting forces tighten the fit on the guide. This way the outer guides on the saddle can pass both the headstock and the tailstock and cutting forces are applied within the length of the guides. Some machines fall short of this ideal as the guides can't pass the head so cutting forces are applied right at the end of the guide. The other advantage of this type of set up is that the weight of the saddle causes it to sit firmly on the guides, no clearance at all – cutting forces just increase the pressure there. It's also easy to get relatively large bearings surfaces.

John

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[Brian AbbottParticipant @brianabbott67793]

Thanks all for the advice, I have ordered a piece of 1mm ground stock and am going to try the suggested.

Whilst on the topic of my old worn out myford, mine has always had a noise from the headstock spindle area, would it be feasible that there is wear between this and the belt pulley ?

Any myford experts out there fancy a new challenge and a trip into Brum, always welcome..

[CotswoldsPhilParticipant @cotswoldsphil]

Morning Brian,

I don't know about different materials and wear – others more qualified may wish to comment.

However, the 1mm shim you propose should give you about 0.005 inch (there – mixed dimensions again!) clearance for the narrow guide face based on an average of the rear clearance measurements you obtained of 31 / 39 thou.

When you refit the apron you will hopefully have sufficient waddle room in the cap-screws to get the rack gearing and half nuts aligned. When I refitted the saddle I moved the apron as near the tail-stock as possible, engaged the half-nuts, made sure the apron was not skewed by reference to the mating edges of saddle and apron and tightened up the saddle. Moving the saddle back to the chuck end and reengaging the half-nuts did not show any significant movement of the lead-screw indicating that the apron was (most likely) aligned OK.

What this mod does is to move the saddle away from the operator restoring it to the designed position. With wear and adjustment, the saddle is slowing moving towards the operator and twisting. The important thing is not to introduce too thick a shim which will over compensate for the wear.

I'm no expert, this is all from the experience of making a simple mod to restore accuracy to a narrow-guide Super 7 or ML7 for that matter.

As I indicated in an earlier post my initial experiment was to test the feasibility of using Turcite with no machining. The 0.5mm temporary shim is still in place and working well, I bent a small lip at the tail-stock end to help locate it. I thought about adding a fixing screw, but the shim has never moved.

Phil

Edited By CotswoldsPhil on 18/09/2015 11:55:40

[Brian AbbottParticipant @brianabbott67793]

Hello all,

well I've been up the shed tonight to strip this saddle off..

oh, dear..

There is a definite .004 step where it's worn.

debating now whether to clean and put it back together and live with it or get it ground..

[millingheadParticipant @millinghead]

Brian

Why not file/scrape the guide shear until the end with the 0.004" wear is back in contact, use unworn rear face on saddle as a reference and some micrometer blue on the bed to show where to remove material, when you have contact along the face do a light scrape in the middle to hollow out the shear, this should eliminate any rock. Just make sure everything is clean as the iron on these machines is very soft and easily scored. (And scraped) . Nothing to lose everything to gain.

Graham.

[CotswoldsPhilParticipant @cotswoldsphil]

Hi All,

Has anyone else done the shim mod and want to tell us about it? What material did you use?

Regards

Phil

[Neil WyattModerator @neilwyatt]

The 'narrow guide principle' as used on older English-pattern lathes (i.e. width front to back much less than length along the bed) is simple – such guides should be much less likely to jam and more accurate in their guiding than wider ones.

In practice, has anyone here ever experience jamming of a lathe or mill table with widely spaced guiding surfaces?

That said the 'guide' of an inverted -V bed as used on American (or Chinese!) style lathes is even narrower in proportion to its length and brings other advantages as JW1 points out.

Neil

[Brian AbbottParticipant @brianabbott67793]

I will try and post a photo later showing how bad the wear is,

the worst wear is between the saddle and the top face of the bed, there is a step between this and the unworn section.

[Clive HartlandParticipant @clivehartland94829]

It sounds to me as if the lathe in question has been used for extensive milling and the saddle has not been clamped down and fretted away the bed in that one position. I cannot see the bed wearing unevenly as used normally?

Clive

[jason udallParticipant @jasonudall57142]

Brian..” bed seems very good, so why is the saddle so worn”..
Not specific to myford ..
But saddle say 70-80 mm of contact…bed about 800 mm …
Though in practice most travel is over the first 100 mm near headstock. ..
This means even if the two wore at same rate..bed has more length to share.
Any way the bed isn’t adjustable un like the saddle..thus can never suffer from “over enthusiastic” adjustment of the fit..imagine headstock end is made very tight..and trailing edge left loose…
All the wear concentrates on one edge of the saddle..allowing it to rock and wear futher..
Also saddle is removable. So would be surfaced with the (hopefully) more likely to wear bit since it could be fixed or replaced. .

[egaParticipant @ega]

In answer to CotswoldsPhil, I modified my S7 saddle many years ago with a simplified version of JAR's method: essentially, just inserting a strip of gauge plate between the rear step of the saddle and the (unworn) rear shear. Whether one follows JAR completely or not, his article is well worth reading for anyone with a worn Myford saddle.

I would also recommend dowelling the front gib strip to prevent lateral movement against the adjusting screws and making up a new, full-width, felt wiper to the saddle.

Neil Wyatt: so far as I am aware, I've never suffered from jamming and the saddle still moves very sweetly the full length of the bed. JAR's article is reprinted in the TEE book but I wondered if it could be made available on the website (if not already)? Another thing I would like to see is an authoritative explanation of how and why Myfords came to see the light. I'm guessing that the Seven's saddle was designed as a development of earlier, shorter, Myford saddles and so "inherited" that wear-prone front step.

[AjohnwParticipant @ajohnw51620]

Tuctite in the UK

**LINK**

It might be worth asking these people what it would cost to regrind it and fit some sort of wear strip. This is the sort of thing you could do yourself with a miller but it will need very careful setting up. I'd just look at adding pads at each end and would probably have to finally fit by hand.

There are several things that can improve these machines when worn. One of the gib strips that hooks under the rails can be turned over. The other has to be reground or a new one fitted. These can then be shimmed for min clearance. Feeler gauges can speed that up but the thickness derived from that may need more adjustment. The trouble is that there is likely to be wear on the underside of the rails / top as well. Best check with a mic first as even few 0.0001"'s matter. Same with the fit of the part you have noticed is worn. People have lapped this sort of thing away in all cases including the cross slide which has similar problems on all lathes, Ordinary gib strips are probably best replaced but regrinding can remove wear. They may finish up bent slightly but this will cure over time if the adjustments are checked now and again.

When I retired some one who regularly gets enquires concerning sorting myfords out suggested I should do that for a "living". The problem as I see it is that once wear has caused significant problems it would be possible to improve things a little for people purely via adjustments but that would only improve not fix it. Past that I feel it would be hard to compete with what myford offered especially in terms of a bed regrind and saddle refit and grind. There would be no chance of matching that doing it by hand. I decided to be short of money and happy rather than going around pissing people off. Suppose I am too honest.

A note cause people don't seem to appreciate this for some reason and it is why this type and dovetails wear.

There has to be some rock on this style of bed because there must be clearance for the saddle to move. It should tend to be on the leading edge on the front as cutting pressures will force that corner against the rail and the opposite on the inner guide – but in real terms there can be wear at both ends. A good quality parallel might show a flat bit in the middle to use as a reference. If scraped the thickness of blue that needs to be used for the accuracy needed is so thin it's not that easy to see. Personally I would use files and maybe a diamond lap. Rifflers are likely to be handy – good sharp ones. Myford hardened beds really are. Diamond laps and honing oil might be the best option if the thickness of the rails via the underside needs changing in places.

The best answer really is to keep them well adjusted and not wait until problems start to show. That way the oil film has a chance of doing it's job.

John

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[Neil WyattModerator @neilwyatt]

> Neil Wyatt: so far as I am aware, I've never suffered from jamming and the saddle still moves very sweetly the full length of the bed.

I very much doubt that anyone has, I think the 'narrow guide' is more relevant to plugs in tubes than lathes, which even Myford tacitly admitted by changing the design.

> JAR's article is reprinted in the TEE book but I wondered if it could be made available on the website

I think TEE might object to use putting bits of their publications on our website! However if someone can dig out the original article from ME…

Neil

Edited By Neil Wyatt on 19/09/2015 12:12:01

[Neil WyattModerator @neilwyatt]

You're in luck – I have the issue here (many of the books about the hobby over the years are largelycompilations of articles from ME or MEW). Hope this helps, Neil.

[CotswoldsPhilParticipant @cotswoldsphil]

ega… Can you remember what thickness of shim was required on your machine? On mine it was 20 thou to create a small working clearance on the narrow-guide. There is a significant difference between Brian's saddle and the one on my machine; the spare saddle I have is <>30 thou similar to Brian's. However, the front space for the gib is <> 0.225 in both cases when adjusted correctly. I'm trying to establish what the manufacturing dimensions might have been.

I've added inserting a dowel to the gib on the todo list, sounds like a good idea.

Neil, My modified wide-guide saddle (with shim) moves sweetly along the bed, either pushed by hand or driven with the hand-wheel and I have never noticed and tightness / jamming. Neither does it appear to twist when you change direction.

Anyone know the book title which contains JAR's article? 

Regards

Phil

Edited By CotswoldsPhil on 19/09/2015 13:47:32

Well slow typing.  Neil beat me to the information. Thanks.

Edited By CotswoldsPhil on 19/09/2015 13:49:07

[AjohnwParticipant @ajohnw51620]

LOL I'm glad you found something that illustrates what I mentioned Neil cause often in the few cases I have mentioned it I know I am pissing into the wind. There are always comments about mine doesn't jam etc. Actually some rock helps after a fashion as the tool on some lathes pulls away from the work when the saddle is wound back masking initial bearing wear problems.

Myford's narrow guide is better than many actually but has the wear problem. It has a huge area to take downward forces but not so good for any sideways ones. I phoned them once about buying new S7 spindle. Turns out that they had never supplied one but they did make some later. The conversation moved on to wear and they couldn't understand how it was happening because they had 30 odd year old machines used regularly that were still fine – the reason is simple really maintenance of the right type when it's needed. That has to include adjustment. I needed a new S7 spindle because some twink had used it for a long time and never adjusted it, probably didn't make sure the oiling was working correctly either. Trying to scape the cone back in to a badly worn spindle would be a waste of time. Actually I'd guess this area is why people have a lot of trouble adjusting them. The S7 is an amazing bit of kit when everything is as it should be. ML7's too but the bearings on those do need attention from time to time and I have often see them with no shims left under the bearing caps.

Personally for all sorts of reasons I feel a wear strip and the front rail narrow guide is the best option but if people do this and also reshim the saddle and sort out the gib strips they probably will find some work is needed on the rails as well. I suspect I have read that Tubal Cain converted a wide guide back to narrow if so he must have been an idiot just like me too.

John

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[egaParticipant @ega]

CotswoldsPhil:

As far as measurement without dismantling goes, about .032".

The book is "Improvements and Accessories for your Lathe" and contains reprints of many, some very ambitious, projects originally published in ME. It also contains a purported photo of "the author in his study" which was in fact of the late H A Taylor; I don't know if this has been corrected in any subsequent edition,

John W1:

I don't claim any particular expertise here and, of course, accept that there must be some swivelling of the saddle under load. So far as lubrication is concerned, I am a long term fan of Rocol Ultraglide despite its expense.I'm not sure if anyone has mentioned that the narrow guide setup means that the tailstock shares the inside edge of the front shear with the saddle step which may aggravate the problem. As I understand it, and I welcome enlightenment from others, Myfords changed their design from narrow to wide and, from what you say, did so against their better judgment. I have great respect for the views of the late T D Walshaw and would be interested in knowing his reasons for converting wide to narrow. Narrow is obviously better if it can be made to work and it may be that proper adjustment and lubrication can achieve that. I remain on JAR's side of the discussion.

Neil Wyatt:

Many thanks for so promptly granting my wish and I hope it helps the OP amongst others.

[CotswoldsPhilParticipant @cotswoldsphil]

ega – Thanks for that. My machine's serial number is just before the change to wide-guide so that may explain the difference in dimensions.

Neil – Thanks for the article – which seems to advocate both narrow and wide guides being brought into use at the same time? unless I have interpreted it incorrectly.

John – Thanks for your observations on the logic behind narrow-guide.

Perhaps when I rework the spare saddle, I should insert a wear-strip of Turcite to the face of the narrow-guide and return the machine back to its original narrow-guide design. I always keep plenty of ISO68 on the bed, so lubrication is unlikely to be a problem. Any thoughts as to how a Turcite wear-strip might last in this configuration? Replacing the wear-strip would be reasonably simple once the narrow-guide face has been machined.

Phil

[KWILParticipant @kwil]

The sharing of the rear face of the front shear with the tailstock is a point, but the measurements I have carried on various beds never seem to show this the be significant as to wear. If it was, then surely the the fabled "it gets tighter as you move the saddle towards the tailstock" should not be a fact?

Edited By KWIL on 19/09/2015 15:16:15

[Brian AbbottParticipant @brianabbott67793]

Attached is a photo of the underside of the saddle.
I have measured the wear and it does not seems as bad as i first thought but there is a definate step on the shear face.
Having spoken with Brian Caddy, and understanding my own limitations i think i will ask Brian to clean this up on the grinder, if it only take 3 or 4 thou to clean up the shear then this i think will be ok for me.
Would have thought it might be worth while shortening the front gib to the same size as the centre, seems pointless have the extra as this just aids the twist..

[CotswoldsPhilParticipant @cotswoldsphil]

Hi Brian,

The longer gib must provide some support, Myford designed it that way – it just needs careful set up so that it does not skew the saddle. A facing test will confirm the correct setting – and or checking for equal gaps either side of the saddle at the rear.

Good luck with getting you machine back together again.

Phil

[AjohnwParticipant @ajohnw51620]

Some one would need to do some geometry but I suspect that the longer outer guide has the same effect as have an inner guide that was longer – a sort of virtual guide that has a length some where between the two. Don't quote me I'm guessing but it probably works out that way because the length between corners that catch when twisted is longer than if both were the same length as the inner.

Personally I wonder why they didn't fit wear strips. They have been around for some time and I wouldn't have thought the cost of adding them would be that significant.

I've suggested using slideway oil to several people – it helps, even the stuff off ebay which actually is a good one. I recently bought some Lubron Waylube 100 which is a bit thicker as I suspect this MAY be better as it should take more load before breaking down. Most people that have switched to slideway oil admit that the slides feel smoother. It may mean that they are adjusting them as little tighter as well. All it takes is a smear.

John

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