Adjusting Myford spindle bearings

[mickParticipant @mick65121]

I had to remove the spindle of my Super7 in order to release the back gear, which had become difficult to disengage, I then reassembled the spindle and adjusted the bears according to the instructions in the hand book.

The problem now is that the spindle stalls at the smallest cut, which means there is still movement which forces the spindle cone against the front bearing cone. I've adjusted the back bearings in order to push the spindle forward off the bearing cone, then adjusted the spindle lock ring and readjusted the bearings to create zero clearance between the bearing cone and the spindle. It takes a bit more than the 0.250'' release of the back bearing ring to free the spindle, but every time I try to stop the stalling I get the same result. Any ideas, as I can't be the first to have this particular problem. Thanks

[mickParticipant @mick65121]

[DMRParticipant @dmr]

Mick,

If anyone can make better sense of your post than I can, I will have to wait and see what they say!

1. Spindles don't stall. Motors do. If you have variable speed, then do you mean the overload cuts in? Or are you literally talking stalled motor or belt slip?

2. You're not a beginner, so have you done the obvious and tested the ability of the spindle to turn by hand? If it is tight , then you have made the adjustment just that bit too good. Slacken your setting off just a tad.

3. Don't understand the "quarter inch" measurement.

Sorry, but I don't understand fully. It seems like you simply have a tight spindle or a new motor fault.

Dennis

[blowlampParticipant @blowlamp]

Did you remove the rear bearings from the headstock housing?

Martin.

[IanTParticipant @iant]

Mick – I think you are probably doing it correctly (pages 24 and 25 of the manual?) but if you have removed the spindle – are you certain everything went back in the right place (and the right way around).

The spindle adjustment is quite sensitive and I've sometimes taken a few go's to get it right. The spindle only has to "stick" – not be completely "hard" locked on – then you back off the adjusting ring by 1/4" as you say – or 15 degree rotation if that is easier to understand. I don't think an over-tight adjustment would stall the lathe – I'd expect it to run hot before it did that…

Are you sure everything is well seated – were the back gears damaged in any way – I think I'd check both gears carefully (especially the lower one) – and do you know what caused the back gear to be "stuck" in the first place – because I don't recall ever having that problem myself..

Regards,

IanT

[davebParticipant @daveb17630]

The cone bearing does wedge if the rear bearing are incorrectly set. The castellated rings either side of the rear bearing move the spindle in and out, the ring at the left end of the spindle adjusts the rear bearings. Turn both castellated rings towards you(right hand one first) so that the spindle moves to the right and the cone bearing becomes slightly loose, then adjust ring at end of spindle until there is just a little drag (rear bearings) as you turn the spindle by hand, then adjust castellated rings, the left one can be loosened a turn or two, turn the right one away from you whilst turning the spindle by hand until it just begins to tighten up, back off slightly then turn the rear ring towards you to lock. Run the lathe to warm it up then recheck adjustment.

Dave

[IanTParticipant @iant]

Sorry Mick – you spoke of adjusting the gears – so just to be clear – is the problem with back gear engaged or not?

Regards,

IanT

[mickParticipant @mick65121]

Hi. Dave. your explanation is a lot clearer than the manual which didn't make it abundantly clear that the setting of the zero clearance between the spindle cone and the front bearing is achieved using the spindle locking ring and not the the bearing clamping rings. I'll give that a go this afternoon, or when it starts raining, which ever comes first. On reflection stall was the wrong word to use, rotation stopping due to the cutter contacting the work piece, then rotation resuming when the cutter is pulled back would have been better.

[AjohnwParticipant @ajohnw51620]

A long time since I had to worry about this area. This image from a post on here shows why it's a tricky thing to do

It's a two stage adjustment. The bearing position is set by the rings but bearing pre load is set by the nut on the end. So each time the bearing position is moved to pull the front cone in the nut on the end needs slackening off first. Bearing position adjusted and then the bearing pre load re applied. In this case preload mean zero of very low end float. Your not looking for zero clearance on the front cone just a very low number to suit the oil that is being used to lubricate it. Perhaps the best way to do that is to smear some oil on the spindle cone before assembling it. This is likely to be too much. Adjust and run the lathe and then adjust again. You will also probably have to adjust again later on as the oil film settles down over time – best done eventually after the lathe has been running for say 15min at a medium speed. Lathe bearings warm up due to friction which will also thin the oil. After adjustment check for problems at high speed.

Summary – the angular contact bearings can always give zero end float. They also have to position the cone so that it has a sensible oil film to run in when the lathe has warmed up. It wont be possible to do this quickly. People might also find that the cone is too tight really before the lathe has warmed up. It's a matter of compromise if that happens.

Personally on these lathes I think it is worth checking the condition of the angular contact bearings as the adjustment is so easy to mess up. They are designed to be used in pairs with each one the right way round and like all bearings shouldn't have any play when not loaded. Some probably doesn't hurt at all given the way Myford use them but any jitter / ripple when they are pressed home and rotated is bad news. The cone can wear in odd ways as well if the lathe has been used with the bearings incorrectly adjusted – too loose in other words and lubrication is very important.

John

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[mickParticipant @mick65121]

Well thanks for all your help, but after an afternoon in the shed I'm only a little bit further on. I now fully understand the system of adjusting the rear bearings, which is perfectly straight forward when you think about it and the amount of clamping rotation on both the the spindle end clamp and the two bearing rings is very fine between tight and free rotation. I've even had the spindle out again to check every thing, including the direction of the ball race faces are correct. I've adjusted and run the spindle for 15 minutes, then readjusted using the method most recommend, but at the end of the day I still can't take more than a 0.020'' deep cut in FC1 without the spindle stopping, which must mean that the spindle cone is being forced back into the front bearing causing the spindle to stop. I expect that only a couple of ten thousandths of an inch are involved, as there's no end, or radial movement when checked with a DTI. I'll just keep on with the adjusting and hope to get lucky!!!

[Keith LongParticipant @keithlong89920]

Mick – when the spindle "stalls" what happens to the drive belt and the motor?

If the belt slips, have you got it at a high enough tension?

If the motor stalls you could have a fault there.

You might well be chasing your own tail with the spindle bearings looking for a fault that isn't there but somewhere else.

[AjohnwParticipant @ajohnw51620]

If it's not belt slip try tightening the rear nut carefully while checking that it doesn't add much drag by rotating the spindle. There should be some drag but very little. When you are pushing by hand your unlikely to displace the oil as much as a cut will. If you over do it you will find they get rather hot after say running at medium speed for 15-20min. It's a tricky area as lathe bearings may run rather hot on some machines – enough to warm the metal around them.

John

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[AjohnwParticipant @ajohnw51620]

You might find that using the tailstock to push the spindle home will help getting the rear bearings set correctly. If your sure that your tailstock is on centre but a centre on it and press it into the morse 2 on the headstock spindle. The cone on the centre needs to be bigger than the morse 2 hole though.

John

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[JonParticipant @jon]

Used to have same trouble after junking the white metal things.

[Ady1Participant @ady1]

You might find that using the tailstock to push the spindle home will help getting the rear bearings set correctly.

Works for the M series. Put some load on the thrust bearings, make sure the spindle spins freely under load, and adjust the cone bearing until it starts resisting, then ease off a bit

[davebParticipant @daveb17630]

Make sure that oil is getting to the cone bearing. The spindle bearings should be adjusted with the drive belt tension released. Use the castellated rings to move the spindle forward until there is just a tiny bit of play in the cone bearing then give the spindle nose a tap with a soft mallet, check the spindle still turns freely then check the ring nut on the other end of the spindle, the tap can settle the spindle in the rear bearings, the spindle ring nut may loosen off. If the spindle gets hard to turn while you are doing this(because it has moved back) move the spindle forward and repeat until it stays free, then adjust cone bearing as before. It's possible to tell if the cone bearing is too tight by slapping the front of the chuck (motor not running) with the hand, if it's harder to turn the chuck by hand after you've slapped it, cone bearing is too tight.

Dave

[AjohnwParticipant @ajohnw51620]

The aspect that needs thinking about when the rear end is adjusted to get the cone right is that all 3 nuts play a part. The end nut forces the spindle shoulder up against the bearings closing them up. The very rear ring positions the bearings. The other ring just fixes the stuff in place so can be left to last but each time an adjustment is made the other 2 need setting appropriately.

Using the tail stock helps because it's likely to thin any oil film other than probably the one in the cone and it will take up any play in the end ring's thread so it wont move when the other ring is tightened – we hope.

Ideally when the cone is positioned correctly there should be some drag. So after an adjustment with the tailstock applying pressure tighten the ring that keeps things in place, withdraw the tailstock and rotate by hand. If after getting this right the cut is still not adequate just make a very small marginal adjustment to the rear ring with the others loose and then tighten them up in the right order. This all assumes that the rear bearing pair are held tightly together otherwise it falls flat on it's face. Hopefully the tail stock pressure will take care of that. Oil films are measure in 1/10 thou, less in some cases. That should give an idea how much difference a turn of a ring can make.

If the cone bearing in the headstock has worn oval that will mess this up and probably mean that the set up needs to be run a little looser than ideal.

There is a fair chance after doing this that it will need doing again once things have settled down – tiny adjustments again. The viscosity of the oil drops a lot once a lathe is in use for a while and that will make a difference usually loosening bearings but on some with roller races etc they can actually tighten a little. The spindle expands due to heat.

John

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Edited By John W1 on 01/06/2015 23:07:54

Edited By John W1 on 01/06/2015 23:16:09

[mickParticipant @mick65121]

Thanks again for the constructive advice. I doubt its the motor as the lathe worked perfectly well before the spindle was removed. As there's rain and wind of biblical proportions outside at the moment I'll spend the morning in the shed and start by trying tail stock pressure and see what occurs!

[mickParticipant @mick65121]

Sorry to have to bother the collective brains again, but I'm not a great deal further on. I've invested in the appropriate 'C' spanner, which makes the finial sensitive adjustment that much more positive. I'm also following Ken Week's step by step gospel according to Malcom to set the adjustment. There is some improvement, as I can now take a 0.40'' deep cut in FC1 with the saddle advanced slowly by hand, but using machine feed is impossible, as the machining pressure still stalls the spindle, but when the tool is backed off the spindle regains its running speed.

The only thing I can think of is that the adjustment between the front bearing cone and the spindle isn't being positively held in position by the rear bearings and so is moving backwards by ten thousandth of an inch locking the two together when the machining pressure becomes too much for the adjustment. There's no discernable movement on the DTI that would indicate where a problem might be. I've tried the adjustment with slight resistance when rotating the spindle, also free rotation when tightening the RH ring, before the finial locking of the LH ring, both with the same end result of the spindle stalling when taking a cut.

The has lathe worked perfectly well during the five years I owned it, the front bearing and spindle cones looked OK when stripped down, so I shouldn't thing there is any oval wear between the two. Any suggestions would be welcomed as the the lathe is pretty much unusable as it is.

Thanks.

Mick

[Ady1Participant @ady1]

If you put decent loading on the spindle with the tailstock is it still ok?

Yet if you put sideyways loading on the workpiece it still jams up?

Try and isolate the issue again, and support the workpiece with a tailstock centre this time

Edited By Ady1 on 22/06/2015 14:23:05

[mickParticipant @mick65121]

Using a tailstock slows the spindle as well, thats why it has to have something to do with the front bearing, but if its adjusted as per the Malcom gospel I can't think what else to do, I was hoping that someone may have experienced the same conditions.

[Nick HughesParticipant @nickhughes97026]

The adjustment is not at all difficult to get correct and because you seem to be going around in circles, I would suggest taking the spindle out again and double checking that everything is in it's correct place and orientation (i.e. a missing woodruff key that should be in the spindle by the taper).

It does seem to me that the drive you have now is only through friction and not a positive mechanical drive.

And just for the pedants on here, I know the belt drive relies on friction to work.

Nick.

Edited By Nick Hughes on 22/06/2015 15:16:24

[AjohnwParticipant @ajohnw51620]

You say 0.4in cut – 0.8 off the dia ?? – rather a lot for a Myford really assuming free cutting mild steel. From memory the auto feed rate on a Myford is sometimes rather coarse so how much per rev?

To give you some idea big DSG 5hp motor, 3/8" cut, bad chip breaker that crunched up the swarf rather than just broke it up, 1/64" per rev but the swarf measured more like 1/16 due to the breaker, blue swarf, bar around 5in dia and the motor really sang. They do when working hard and make a very distinctive sound.

A photo of the tool tip you are using might help as well.

John

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Edited By John W1 on 22/06/2015 15:40:34

[Nick HughesParticipant @nickhughes97026]

John W1,

Reading mick's earlier posts, I think he meant 0.040" deapth of cut.

Nick.

[Ady1Participant @ady1]

IMO you need to keep moving the spindle forwards with the thrust bearings, until the tailstock loading no longer slows the spindle down

Don't forget to release the tailstock loading between adjustments

Edited By Ady1 on 22/06/2015 16:13:52

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