Evaluating & Correcting Wear in an ML7

[peak4Participant @peak4]

Posted by Dr_GMJN on 28/10/2020 23:09:52

Hmmm tape. This is very similar to the method in Hopper's M.E. Articles, but of course he uses pinned steel instead of tape. The leadscrew would be aquestion mark. I think Hopper suggests machining the brackets back.

Is it worth a try? Probably. £50/metre though….wow.

………………

 

Er, no not £50/m £3.17 +VAT & post for 20mm tape with a sticky back.
Turcite and similar products are rather more expensive.
I bought a metre of tape 100mm wide and cut a slice off, hence having some spare. That was £21 delivered in a couple of days from ordering.
I ordered the wide stuff as I wasn't sure if I need to build up the flat surfaces on the knee of my machine, but got away with just scraping it flat.
It needs a very thorough de-greasing of the cast iron for obvious reasons.
It might not be a permanent solution, but just an exploration of the method.

Also companies like Starrett make feeler strip in 12" lengths; I used some 25thou, but you might be able to get it thicker. Modern adhesives can be quite good.
My thoughts are that arranging for minimum clearance on the short sliding interface will obviate the need for major re-work on the leadscrew etc. At least in the short term anyway, whilst just exploring the suitability of the preferred final method.

Bill

Edited By peak4 on 28/10/2020 23:34:13

[HopperParticipant @hopper]

Posted by Dr_GMJN on 28/10/2020 21:57:16:

Bill,

It's a consistent 0.022" gap at the back of the saddle.

Hopper,

I know this isn't your preferred method, but for someone with my current experience/ability, it's probably a case of it being the best compromise. The current plan is to:

1) Mill the short guide back by 0.030", and undercut the adjacent horizontal face very slightly.

2) Mill or file away the unworn step in the rear horizontal bit of the saddle (next to the currently unused bearing face), and undercut very slightly as per 1). Obviously being very careful to avoid the face.

3) Drill the saddle face and fit new wide-bed felt and retainer.

4) Fit a new front gib strip and hope the gib screws will take up another 0.022" (I think they will)

5) Make and fit a pair of 0.025" shims behind the leadscrew bearing castings to maintain the apron/leadscrew alignment.

6) Refit and adjust – Maybe do the dumbell test bar test.

I wouldn't touch the inner faces of the beds (the tailstock bearing faces) at the moment.

I'm going to trust my metrology here, and predict it won't make a lot of difference, however, there seems little to lose by doing it. The only chance of improvement I can see is it will at least eliminate the lesser of the two wear/bind points (rear of front web). So even if that gives me only another 2 or 3 inches of bind-free travel, the feel of the lathe would be vastly improved, and I could move the tool out of range of my hand when messing about with the workpiece – I have several scars to prove this isn't currently possible!

If I do end up having a re-grind, presumably I wouldn't need the saddle doing if I use this method?

If anyone can see something daft in any of that then, please let me know – plan is to do the deed this weekend.

And again, any recommendations for re-grinders would be appreciated. I assume a Myford job will be the most expensive option.

Cheers!

Edited By Dr_GMJN on 28/10/2020 22:00:37

Sounds like a plan.

Slideway Services has been mentioned on here before for regrinding. I think they went out of business but someone found an alternative or someone took over the business, or something. A search of past threads on here containing "Slideway Services" should reveal more.

[Dr_GMJNParticipant @dr_gmjn]

Quick update – I’ve gone back to my plan’A’ from page 1, and combined it with Bill’s suggestion of feeler gauge material. I’ve ordered some 0.75mm x 12.7mm x 300mm stuff from RS, which I will bond to the rear saddle face with retainer.

I’ll scrape or file any un-worn bits from the horizontal bearing surfaces.

I’ll fit the new gib strip, and see what happens.

When it all shakes out, the feeler gauge strip should give me a net 0.008” saddle movement, towards the back of the lathe. The half-nut should cope with that hopefully.

What are the easiest tests to do once rebuilt and adjusted? There’s the DTI over a face-plate to check for perpendicularity, and the dumbbell test for bed twist. How about a test for tailstock height and horizontal alignment?

I’ll report back with how it goes.

Thanks all.

[Dr_GMJNParticipant @dr_gmjn]

A quick and dirty wide-guide test using the 0.75mm shim steel from RS just now seems to confirm that it makes no discernable improvement at all to the binding issue (as predicted by the figures). Still waiting for the new gib strip, but I doubt that will make any difference either.

Didn't get anywhere with Slideway Services (or their replacement) either, so all a bit disappointing. At least I tried!

[Dr_GMJNParticipant @dr_gmjn]

Assuming that cutting forces are in general pulling the rear saddle face into contact, Would placing short, stiff compression springs between the gib strip screws and the strip itself improve matters, or would it just cause chatter? Im thinking they would compress to compensate for the 0.002" dip, but be stiff enough to resist cutting forces.

[HopperParticipant @hopper]

I wouldnt think so. Any spring weak enough to allow movement will also move under cutting forces. If there is only 2 thou of variation, you should be able to adjust the gib strip with the standard screws so its that 2 thou loose on the worn bit and just clearing the unworn bits without inducing chatter etc. With the wide guide surface giving added stability you might find this works ok.

You could try very carefully easing the high spots off the surface of the front bed surface with a fine flat file, say a 10-inch flat single-cut mill saw file. If the variation is only 2 thou, you might only need to ease one thou off it to get it moving ok.

Otherwise, contact details for Slideway Services are still on the net on their website, but no idea how current that is:

Contact us

Slideway Services Ltd
Unit 24
Hammond Business Centre
Hammond Close
Nuneaton
CV11 6RY

Tel/fax: 02476 327874
Mobile: 07775 683363
E-mail: info@slidewayservices.co.uk

Edited By Hopper on 30/10/2020 11:01:00

[HopperParticipant @hopper]

Some previous discussion on this thread **LINK**

Sounds like if you can get hold of the Slideways Services guy he will put you in touch with someone who can help.

Or there is mention of Birmingham Machine Tool Services also.

Otherwise, there is Myford themselves, but premium price. Not sure how much these days. Youd have to ask them.

 

Edited By Hopper on 30/10/2020 11:14:29

[Dr_GMJNParticipant @dr_gmjn]

Thanks Hopper, yes I already read that thread. I called Slideway Services, but he just said he'd retired. Birmingham M/C Tool Serivces number fails, so no contact there.

I did wonder about flatting the front edge. That would cure it.

Can you file hardened surfaces, or would it be scraping? What would the best technique be?

[Dr_GMJNParticipant @dr_gmjn]

What about a fine flap wheel, followed by some wet and dry/oil wrapped over a 6" long piece of ground rectangular bar?

I already know the distance from the end and the amount I need to remove, ie a pretty accurate profile of how much to remove and where. I could use calipers as a go/no-go gauge.

[HopperParticipant @hopper]

The bed is not hardened so files easily.

Don't you dare attack your lathe bed with an abrasive flap wheel. It will dig trenches all over the place. All you need to do is ease about one thou off the highspots. Large flat file will do that if used carefully with restraint. Its a bit of a bodge but better than regrinding cost wise and in theory this is a clearance surface under load so …

[Dr_GMJNParticipant @dr_gmjn]

Posted by Hopper on 30/10/2020 11:33:54:

The bed is not hardened so files easily.

Don't you dare attack your lathe bed with an abrasive flap wheel. It will dig trenches all over the place. All you need to do is ease about one thou off the highspots. Large flat file will do that if used carefully with restraint. Its a bit of a bodge but better than regrinding cost wise and in theory this is a clearance surface under load so …

Understood.

[Ex contributorParticipant @mgnbuk]

The usual way to remove small amounts from a face would be to scrape it – at the rate I scrape (with a sharp carbide scraper), that is around 1/4 of a thou per pass.

A known good flat reference that is longer than the face to be scraped & some marking blue (NOT layout blue) will show the high areas on the bed face, but a shorter flat piece to apply the blue used with your surface gauge & indicator arrangement to look at the bigger picture would also work. Less chance of taking too much off , rounding or tapering the face that way than with a file.

I did the "wide guide" conversion on my mid-60's Super 7 with a piece of 1/16" x 1/2" gauge plate Loctited to the rear of the saddle. It hasn't come loose in the several years since I did it & no machining of the old "fast side" on the saddle was required. There was so much wear to that short face that it was well clear when the gauge plate was inserted. There was also sufficient clearance in the apron securing screw holes in the saddle for the apron to be replaced without modification.

Good luck,

Nigel B.

[Dr_GMJNParticipant @dr_gmjn]

Posted by mgnbuk on 30/10/2020 12:07:12:

The usual way to remove small amounts from a face would be to scrape it – at the rate I scrape (with a sharp carbide scraper), that is around 1/4 of a thou per pass.

A known good flat reference that is longer than the face to be scraped & some marking blue (NOT layout blue) will show the high areas on the bed face, but a shorter flat piece to apply the blue used with your surface gauge & indicator arrangement to look at the bigger picture would also work. Less chance of taking too much off , rounding or tapering the face that way than with a file.

I did the "wide guide" conversion on my mid-60's Super 7 with a piece of 1/16" x 1/2" gauge plate Loctited to the rear of the saddle. It hasn't come loose in the several years since I did it & no machining of the old "fast side" on the saddle was required. There was so much wear to that short face that it was well clear when the gauge plate was inserted. There was also sufficient clearance in the apron securing screw holes in the saddle for the apron to be replaced without modification.

Good luck,

Nigel B.

Thanks Nigel,

Yes, the 0.75mm shim steel has the same effect on mine – makes the short bearing clear its bed face – no machining required. Intention is to bond it with retainer.

I just need to flatten that front face slightly.

I've never done scraping before so I'll try the file method – carefully!

There is a region of the front bed (far right side) which still has has its machining marks, and never gets used, so I'll practice on that area first, and see how much gets removed per stroke.

[peak4Participant @peak4]

If you want to practice scraping, rather than doing it on the back of the bed, perhaps try on a length of spare continuous cast iron bar.
That was the first thing I made on the way to re-scraping my grinder, and used it both on the flats and the dovetails.
In my case I didn't use continuous cast, but took a slice of a cast iron bus bar fishplate clamp.

Strikes me that there are two advantages there,
one you aren't changing the lathe,
and two, when you are happy enough with your technique, you will then have a straight and flat straight edge to use on other jobs.

I wonder if your front shear is more worn than usual is it was because a previous owner primarily used the lathe for boring work, where the forces were in the opposite direction to external turning.

Re. bed grinding, I gather you followed by link to Garside's machinery moving web site, but were you able to access the Facebook link.
The latter has a photo of them grinding Myford beds, and a discussion of pricing for larger work.

Bill

[Dr_GMJNParticipant @dr_gmjn]

Posted by peak4 on 30/10/2020 14:30:03:

If you want to practice scraping, rather than doing it on the back of the bed, perhaps try on a length of spare continuous cast iron bar.
That was the first thing I made on the way to re-scraping my grinder, and used it both on the flats and the dovetails.
In my case I didn't use continuous cast, but took a slice of a cast iron bus bar fishplate clamp.

Strikes me that there are two advantages there,
one you aren't changing the lathe,
and two, when you are happy enough with your technique, you will then have a straight and flat straight edge to use on other jobs.

I wonder if your front shear is more worn than usual is it was because a previous owner primarily used the lathe for boring work, where the forces were in the opposite direction to external turning.

Re. bed grinding, I gather you followed by link to Garside's machinery moving web site, but were you able to access the Facebook link.
The latter has a photo of them grinding Myford beds, and a discussion of pricing for larger work.

Bill

Bill,

That's an interesting theory about the boring operations. The thing is, the lathe always seemed in pretty good overall condition for its age (0.002" wear on one slide isn't huge I don't think for a 54 year old machine), and the person who owned it immediately before me used it for making steam engines and narrow gauge locomotive models, so a range of turning jobs. It's history before that is unknown of course.

I couldn't get any information from the Garside website or Facebook page, but gave them a call. I am sending some photographs and my measurement data by email, and they said they'd get a price for me.

I have to say though, I spent about 5 minutes with a fine file earlier on this morning, used very gingerly flat-on to the face, and already I can get the saddle to more than 3/4 of full travel with no significant tight spots or play. This amount of work didn't even bottom out the machining marks on the right side of the bed, yet it seemed to make a huge difference. I could feel (but not see) a very slight roughness along the top corner of the vertical slide, which I smoothed off. I wonder if that was contributing to the issue somehow?

My intention is to now do a much more detailled filing, measuring and flatting session, remove the saddle steps (not that I can actually see or feel anything significant), fit the new gib strip and re-evaluate.

I'm currently a lot more optimistic about being able to sort this out myself than before. I was always surprised that less than 0.002" would cause the degree of binding I was experiencing.

[Ex contributorParticipant @mgnbuk]

I was always surprised that less than 0.002" would cause the degree of binding I was experiencing.

Wait until you get to play with dovetails – doesn't take half that to get them stiff.

Nigel B.

[Dr_GMJNParticipant @dr_gmjn]

Posted by mgnbuk on 30/10/2020 15:54:25:

I was always surprised that less than 0.002" would cause the degree of binding I was experiencing.

Wait until you get to play with dovetails – doesn't take half that to get them stiff.

Nigel B.

Next job after the saddle is re-fitted is to put re-settable dials and needle thrust bearing conversions on the top and cross-slides. I got a new cross slide gib strip to fit too. I don't think they're bad to start with though – never had any issue with them apart from the crappy feeling and backlash in the wheels/cranks.

[peak4Participant @peak4]

Posted by Dr_GMJN on 30/10/2020 15:34:47:

Bill,

………………………

I couldn't get any information from the Garside website or Facebook page, but gave them a call. I am sending some photographs and my measurement data by email, and they said they'd get a price for me.

…………………………

Not Garside's Facebook page, the link I posted in the last post on P2 of this thread, which was to the Myford Facebook Group. It was a general posting, but didn't include a Myford price.
You need to join the group to be able to read posts on there.

Bill

 

Edited By peak4 on 30/10/2020 18:01:33

[HopperParticipant @hopper]

Posted by Dr_GMJN on 30/10/2020 15:34:47:

Posted by peak4 on 30/10/2020 14:30:03:…

…I have to say though, I spent about 5 minutes with a fine file earlier on this morning, used very gingerly flat-on to the face, and already I can get the saddle to more than 3/4 of full travel with no significant tight spots or play. This amount of work didn't even bottom out the machining marks on the right side of the bed, yet it seemed to make a huge difference. I could feel (but not see) a very slight roughness along the top corner of the vertical slide, which I smoothed off. I wonder if that was contributing to the issue somehow?

That sounds pretty good. You don't usually need to move the saddle that last quarter of the travel to the right so I would leave it at that. The less metal removed the safer. But it could be binding in that top corner. You can safely file a small chamfer along there for clearance without it affecting the bed dimensions negatively. It may be binding some on those corners on the unworn part of the saddle.

Dont get too carried away with trying to eliminate absolutely all play. Many a lathe with more than your 2 thou wear has the saddle set to the tight spots and allowed to run a bit loose on the worn spots and it generally works ok. Under cutting loads, the saddle is pushed into contact with the guiding surface.

Scraping is good but not practical for an inexperienced beginner in an instance where a few file strokes will carefully do the job.

[Dr_GMJNParticipant @dr_gmjn]

I think this might have worked. I used the Excel graphs as a reference for filing, and set up the DTI again on the rear vertical as a checking method. I just used the fine file and a 6” gauge block wrapped in #800 paper lubricated with 3-in-1 oil:

The feeler gauge material happens to be 1/2” wide, so a perfect fit for the rear bearing surface. Mine has shims inserted under the retainer strip, so that’s guaranteed some clearance. I Had to saw it to length and polish up the cut end. It’s secured with retainer. I also filed off the old wear edges from the horizontal faces. I might clean those up a bit more:

After cleaning everything with degreaser I test assembled it, and I can now easily move it all the way to the right, with some very slight binding towards the very end of travel at the chuck. This tallies with the graph, but not the DTI. I think this therefore might be a bind on the old short bearing. I measured 0.003” clearance at the tailstock end with the new bearing shin fitted. I’ll double check it at the chuck end tomorrow.

According to the DTI I’m less than 0.001” of flat at present. I’m not going to pretend it’s consistent handwheel resistance all the way, but it’s very close. A massive improvement. Hopefully I can get it even better with some further work at the chuck end, the new gib, and some proper slideway oil.

Not bad for 30 minutes’ work. The real test will be the faceplate, perpendicularity and taper turning checks…

Thanks for sticking with me all!

[HopperParticipant @hopper]

That sounds good. Well done.

Yes I would machine at least 30 thou off that old narrow guide surface. Otherwise, you will surely get swarf in that 3 thou gap and cause binding or skewing of the carriage.

Gib should be set loose enough that you can slide the saddle freely without resistance along the bed by pushing gently by hand on the saddle without the apron and handwheel in place. Binding between the handwheel, its pinion gear and the rack can give a false "feel".

When you have the apron back on, you can loosen the rack screws and position the carriage first at one end with a slip of paper between pinion gear and rack and tighten up rack screw at that end.then repeat at the other end of the bed. This ensures clearance between rack and pinion gear along the full length of the travel.

Also make sure the half nuts are not rubbing on the lead screw causing binding. They are adjustable with a small grub screw uin the lower half nut to set clearance. Make sure the operating handle pivot spindle nut is tight enough to hold the handle in the disengaged position.

It would be good to double check your across the full width of the bed measurements with a mike too. The sled and DTI method can be subject to some error if the top surface of the bed way is not perfectly flat, kicking the arm that holds the DTI at an angle and affecting the reading by a small amount.

[peak4Participant @peak4]

Nice one, it's looking quite good at that.
I'll get around to doing mine at some point, but obviously using the tape, as I have it in stock.
Currently making a batch of arbors for the grinder at the moment.

Re your comment on oils.
Don't know if you're aware, but Pennine Lubricants are reasonably priced for slideway, and hydraulic oils, (and also for cutting oils in their Metalwork section).
I'm using their neat synthetic cutting oil in my larger Warco GH1330 as well as their slideway oil on all my lathes.
The Nuto equivalent hydraulic oil on the other Myford bits, and a soluble oil in an old hand sprayer for the power hacksaws and grinder.
They are at the top end of the old Batchelors pea factory off Claywheels Lane.

Bill

[Dr_GMJNParticipant @dr_gmjn]

So the new gib strip arrived from Myford. It’s not like the original, which had recesses neatly machined in it to suit the rounded-end gib screws. This one just has two rather ragged looking holes in it which don’t appear to line up with anything:

If I line it up with the closest screw, it sticks out the front and the felt retainer doesn’t fit:

If it’s not aligned with any bolts it just slides out the end when moving the saddle? Any ideas on this, apart from the saying about a fool and his money?

Anyway, the short guide is machined back 0.0030” and so there’s no going back now:

Also drilled the saddle for the new wide-guide felt retainer.

Thanks all.

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Dr_GMJN on 31/10/2020 15:22:20:

[…]

Myford. It’s not like the original

[…]

.

So it would appear

MichaelG.

.

Apologies for quoting just those few words … but I think you will see my point

[Dr_GMJNParticipant @dr_gmjn]

Posted by Michael Gilligan on 31/10/2020 17:36:15:

Posted by Dr_GMJN on 31/10/2020 15:22:20:

[…]

Myford. It’s not like the original

[…]

.

So it would appear

MichaelG.

.

Apologies for quoting just those few words … but I think you will see my point

So I bought it off EBay (From Myford) as a Standard Length (four T slot) Saddle Gib Strip for ML7, ML7-R etc.

After consulting my parts list in the old Manual it seems like there might be one digit difference in the part number prefix.

No note as far as I can see on the listing that warns that there might be two types.

So now I’ve got to measure the existing dimple centres, and drill it myself. And I’ve paid £14.40 for a piece of steel that would have probably cost me less than £1 from my materials supplier.

Thanks Myford.

[Author]

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