Shimming Myford ML7 spindle

[Alan Thomas 7Participant @alanthomas7]

[Alan Thomas 7Participant @alanthomas7]

I have searched the forum and it is obvious there are people with knowledge on this topic but none of the old posts covers the point I want to raise.

I have an early (1948) ML7 with history unknown which seems to have very little wear and no damage, I have been using it for a few projects over the last 5 years but recently realised the headstock bearing caps screws were loose. I loosely tightened the caps and the spindle locked up.

I removed the caps, pulled out the spindle and found both spindle and bearing were in 'as new' condition. I measured the shims, they were the laminated type, all to be 17thou .

Thinking someone had removed too many laminates I ordered new shim packs from Myford and were surprised to find that the new ones were also 17thou. I then replaced the bearing caps without spindle and shims and tightened the caps until the white metal bearing halves were touching each other and measured the gap where the shims would be, it was 16 thou. So even with new shim packs I was only going to 'space' the bearing by 1 thou at the most?

The bearing caps showed no evidence of filing of any post manufacture machining so what’s happening?

I think at some time in the recent past it was fitted with new spindle, shim packs and white metal bearings (before they became unavailable) and the last owner found the spindle locked without any of the shims being torn off so he simply left the screws loose.

Anyone else had this problem, the only solution I can see is to just add the new shims on top of the existing then rip off until correct adjustment.

– Alan

[Brian WoodParticipant @brianwood45127]

Alan,

Welcome to the forum, what a fortunate man!!

I don't really think you have a problem—does the spindle exhibit any lift when the bearing cap bolts are loose?

If it does you could do worse than peel off a shim and replace it with two pieces of printer paper instead, they are roughly 0.004 inches thick, added together they will be about half a shim thickness. It is better in my opinion to keep the bearing gap closed, even if only just so that you can pull it down 'solid' onto the shim pack

I hope that helps. In the meantime enjoy the rarity of the machine you have found

Regards Brian

[Kiwi BlokeParticipant @kiwibloke62605]

If your measurements are correct, there seems to be a misalignment or, more probably, an out-of-roundness of the bearing shells. Time to get out the 'blue' and check everything, and scrape the bearings. Plenty of instruction on the 'net (and in books…) about scraping. Some of it can be believed…

[Robert ButlerParticipant @robertbutler92161]

Dear Alan

Have you checked the adjustment provision on the mandrel to the left of the headstock, if this is over tightened it will tend to draw the mandrel further into the tapered bearing on the right of the mandrel. I am not sure of the adjustment procedure and as i have sold my ML7 with handbook cannot check the correct method. It is possible to download handbooks or even buy them.

Robert

[Kiwi BlokeParticipant @kiwibloke62605]

To avoid confusion, ML7 bearings are parallel. It was only when the ML7R came along that a tapered bush was used. However, it's worth slackening off the thrust (end float) adjustment just to remove one possible cause of binding…

[Robert ButlerParticipant @robertbutler92161]

My apolagies, quite correct but it is quite some time since i dismantled the mandrel and in deed owned an ML7 the S7 which I now own does have a tapered front bearing.

Robert

[HopperParticipant @hopper]

Sounds like you need a couple more shims in the one to 1.5 thou range. You can peel them off your new pack, or cut them out of some brass shim stock, or specialised plastic shim stock. Being a bit old-fashioned, I wouldn't use paper. It might compress under load, and might be degraded by the inevitable oil.

To get fine adjustment, you can add a shim under one side but not the other. Gives more-or-less "half a shim" of adjustment. Add shims until the spindle spins freely with about half a thou of measureable up and down behind the chuck, with the cap bolts tight. You can get the last few tenths of a thou adjustment by tightening the bolts a little extra, but not too much. There is some tiny amount of "give" in the shim packs.

I wouldn't go scraping bearings etc that have been working perfectly and are bedded in to that spindle. Best to keep things simple. Bit of shim will do the job.

Edited By Hopper on 12/01/2020 01:52:53

[Kiwi BlokeParticipant @kiwibloke62605]

As Hopper suggests, a 'bit of shim will do the job'. Probably. Possibly. But will it do a really good job?

Remember that cutting and drive belt forces will tend to lift the spindle, so the upper shells will tend to wear most, making the hole through each pair of shells not round – if it ever was (and it most likely wasn't). 'Adjusting' the bearing clearance will increase contact with the lower shell, but probably not over much area. The upper shell may well have worn to produce good contact with the spindle, but there's no guarantee that the lower one has.

You should be aiming to have as rigid a bearing housing as possible, so this means the cap bolts tight. You should also aim for good bearing contact over the whole bearing area, again for rigidity. This explains my belief that scraping will probably be necessary. It was, after all, standard practice when these lathes were designed: white metal bearings get scraped.

Another reason for wanting the best bearing fit achievable is to stop oil piddling through the bearing and going to waste.

[HopperParticipant @hopper]

Posted by Alan Thomas 7 on 11/01/2020 12:14:49:

I removed the caps, pulled out the spindle and found both spindle and bearing were in 'as new' condition.

In that case, I'd be reluctant to put an inexperienced scraper to them. If it ain't broke, don't fix it. Shim and carry on lathing.

[Robert Atkinson 2Participant @robertatkinson2]

You can't tell f the bearings are fitting properly unless you get some blue on them. It sounds like the bearings were replaced but not fitted and adjusted properly. They maybe be fine but you can't be sure until you check them.

Robert G8RPI.

[Nigel McBurney 1Participant @nigelmcburney1]

I had a brand new ml7 back in 1968, ad it proved to be very accurate,and turned/bored truly parallell.indeed far better than a replacement new super 7, it did have one annoying fault,when running after a while on top speed which if I remember correctly was around 600 plus,the bearing would get warm and the spindle get tight in the bearings,at lower speeds it was ok,in five years use it did wear in a little and would run for longer periods without getting tight.did Myfords set them tight or was mine set up on top/bottom limit. I would not attempt to scrape in a such a relatively small white metal bearing,it is so easy to upset the alignment,I would prefer to shim the top cap cap,get some brown paper and make a shim and see how it runs,there is nothing wrong with paper shims and it lays flat,whem making brass shims and cutting them to shape and punching holes can distort the edges of the brass,its good enough for vintage engines which need a bit of clearance,a paper shim will not cause distortion of shell or bearing cap of the lathe.

[Alan Thomas 7Participant @alanthomas7]

Thanks Guys for all your thoughts and advice. I am sure scraping would be the 'professional' way to go but i don't have a scraper small enough to do the job and I am disinclined to practice on bearings that are no longer available. I just checked and a replacement spindle and new bronze bearings (have to replace spindle with new bronze bearings) would be more than I paid for the lathe.This and the fact that the bearings are not worn lead me to additional shimming.

I took out the spindle , cleaned all traces of oil then reassembled with the original shims but left both caps loose and working on one end at a time inserted feeler gauges either side of the cap in addition to the shims already in place. You can lay the feeler along the entire length of the cap outboard of the screws. I started with 0.010" this was very loose, jumped to 5 thou then reduced by 1 thou at a time, tightening down on each step and measuring the play with a DTI by gently levering the chuck end of the spindle with a piece of wood up and also side to side. I got down to a 3 thou feeler either side on the chuck end cap and a 2 thou feelers on the other end. With these feelers in place I could just turn the spindle by the chuck thread with my fingers.

'Steve Vine 1' on this forum sent me a msg suggesting using kitchen foil to provide the extra shimming. What a great idea I tried and you can punch the hole with a paper hole punch and cut the stuff with scissors. measured the foil we had and it is near as damm it 1 thou thick.

Made up the shims required, fitted, tightened down the caps, tested for play with the DTI and all is good, job done. All oiled up and I do have a job that will require running for some time so I will monitor if bearing gets warm. Too warm and I'll add another 1 thou foil shim.

Anyone want to buy a genuine unused pack of Myford laminated shims cheap?

Thanks again guys – Alan

Edited By Alan Thomas 7 on 12/01/2020 11:00:10

[HopperParticipant @hopper]

Good job well done!

If it were to run a little warm in the long run, you could possibly loosen the screws off just a tad. It does make a difference of that tiny last bit that is sometimes needed.

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