Myford ML7 mandrel diameters?

This topic has 12 replies, 6 voices, and was last updated 25 May 2017 at 11:55 by Hopper.

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23 May 2017 at 17:05 #299362
Andrew Tinsley
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@andrewtinsley63637
Does anyone know what the diameter of the ML7 mandrels is? I have reached the stage of installing the new white metal bearings and the mandrel.

I suppose that I am getting nervous and just hoping the bearing diameters are "within spec". The bearing areas are free from any major scoring. In fact they look remarkably polished and uniform. I have not yet "miked" them up for fear of finding them appreciably undersize!

I know I should just install things and see what play there may be. The only snag with this approach is that I have never scraped white metal bearings of such small size! I have done full size loco bearings before, but they are hardly in the same league for accuracy!

As I was fortunate enough to get a brand new set of white bearings, I just don't want to ruin them!

Andrew.
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23 May 2017 at 17:05 #8727
Andrew Tinsley
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@andrewtinsley63637
23 May 2017 at 18:24 #299372
duncan webster 1
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@duncanwebster1
I always understood that ML7 bearings were thin shells, like car big ends, and not supposed to be scraped. Mine had a shim pack between top and bottom, keep peeling them off until it was right
23 May 2017 at 19:08 #299381
Lambton
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@lambton
Andrew,

Do you know about Plasigauge which a very simple product that allows bearing clearances to be accurately measured without the need for any measuring tools!

Link **LINK**

I used it a lot back in the day when I rebuilt all sorts of engines.

Eric
23 May 2017 at 19:27 #299382
Robbo
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@robbo
Duncan,

You are correct about the shells, but every time 0.002" of shim (that is 1 lamination) is removed from the packing, then the white metal should be scraped, mostly at the top and bottom, to retain "roundness" and keep a good all round seating.
24 May 2017 at 08:43 #299425
Tony Pratt 1
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@tonypratt1
Hi Andrew,

Have you looked at the you tube video [s] on this very subject?

Tony
24 May 2017 at 10:05 #299430
Andrew Tinsley
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@andrewtinsley63637
Hello Robbo,

That is the thing that bothers me! Scrapping at the top and bottom of the bearings is something that I feel could easily go wrong and once a mistake is made, then I will probably spiral out of control! The bearings appear to be thicker than the usual shell bearings on big ends and cranks of car and bike engines, so maybe I have more white metal to play with than I think!

I am probably worrying over nothing, but I usually like to practice and become relatively skilled before I tackle something new! I don't even know what sort of small scraper to use on such (to me) small plain bearings!

Tony,.

Regards,

Andrew.

Thanks for the tip, I shall search U tube to see if I can find the clips you mention
24 May 2017 at 11:39 #299446
Andrew Tinsley
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@andrewtinsley63637
Hello Tony,

I can't find anything that is really relevant except for replacing the mandrel with a new Myford hardened version and phosphor bronze bearings. Maybe I am using the incorrect search terms?

Regards,

Andrew.
24 May 2017 at 13:02 #299459
Hopper
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@hopper
They are not thinly layered shell bearings like a car big-end. The ones in my ML7 seemed to be solid cast white metal as far as I remember. So you can scrape the bejayzers out of them and file or machine the mating faces to scrape even more bejayzers out of them when they get too old and worn.

Spindle is unlikely to be significantly worn so maybe clean it up carefully with a strip of fine emery tape by hand and then just blue spindle up lightly and see what sort of reading you get to start with. You might get lucky and get away with just adding the correct shims between the faces along with a light scrape if they are supplied rough machined.

As you can imagine, it takes not very much scraping on these tiny bearings. Gently as she goes. I used a small three-sided scraper with about a six-inch long blade plus wooden handle. All my half-round scrapers from power station turbine scraping days were about six sizes too big!

Edited By Hopper on 24/05/2017 13:13:55
24 May 2017 at 13:09 #299461
Tony Pratt 1
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@tonypratt1
Hi Andrew,

Sorry you are right, the videos don’t help you. Many years ago I made a new spindle & fitted it to a refurbished ML7 using new bearing shells.

From memory the bearing diameters were a nominal size i.e. 1.250", 1.500", 1.750" etc. etc.

First job is to bed the bottom bearings into the casting, blue up the headstock bearing location faces & put in the bearing, if you press down lightly & rotate the bearing slightly the blue will mark the high spots on the bearing shell, you will then need to remove the high spots with a needle file.

Continue the above until you have a decent amount of contact between bearing shell & bearing housing. Repeat on other bottom bearing. Fit the bearing shells.

Lightly blue up the spindle & lay into the newly fitted bearing shells, press down gently & rotate the spindle, the spindle contact points on the bearing shell will be blue.

You will then need to remove the blued high points with a half round scraper & repeat the process until you achieve a decent amount of contact, try to take the same amount evenly off both bearings so the spindle stays parallel to the bed both in the horizontal & vertical planes.

Next fit the upper bearing shells to the caps & bed in as before using a needle file if necessary.

Assemble the upper bearing caps with fitted shells onto the blued spindle adjusting shim thickness until there is a slight drag when tightened down.

Again scrape bearing shell high points to achieve a decent contact area, shims are adjusted to give free movement with no play.

The above makes sense to me & as I say I have actually done this procedure but many years ago, hopefully there are practical scraping videos online.

Any questions let me know.

Tony
24 May 2017 at 13:48 #299465
Hopper
Participant
@hopper
Just double checked the ML7 bearings on the bench in my shed (where they have sat half-scraped in for several months now!) and they are solid cast white metal about 3/16" thick, so scrape away!
24 May 2017 at 16:08 #299474
Andrew Tinsley
Participant
@andrewtinsley63637
Thanks Tony, You seem to have made the job somewhat easier! I suppose it is the usual reluctance to do something new, especially as I thought I may have one shot at getting it correct!

Hopper, thanks for confirming that the bearings are solid white metal, that makes me feel a lot better about doing the job.

The bearings didn't have too much play before dismantling the headstock. There were plenty of shims left , so maybe I could try sorting out the original bearings. It would give me some practice and I still have the new bearings to go at if I make a mess.

I know the history of the lathe from new and the bearings have not been touched since they were installed at Myfords. Now here is an oddity, the shims under the cap nearest the chuck are all the same thickness EXCEPT for the one at front right, which is 7 thou thinner than the others. There is a piece of solid shim (cut exactly to the Myford pattern) the rest being laminated shim. I am somewhat amazed by this. It has been executed very neatly. I can only think that the original bearing must have been distorted during casting, although this seems very unlikely. Anyone care to guess what the reason is for this oddity?

Thanks,

Andrew.
25 May 2017 at 11:55 #299540
Hopper
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@hopper
Shims sound normal. They don't have to have the same size shim each side. Just whatever fits.
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