Myford ML10 spindle runout question

[IgnatzParticipant @ignatz]

I've recently had reason to check the main spindle of my old ML10 modelbuilders lathe. This is one of the early models with the spindle running direct in the cast iron of the headstock casting with full loss oil drip lubrication.

I find that the measured runout on the outside of the threaded mount is about 0.01 millimeter ( = 0.0003936996 inch ). I'm getting more or less the same runout reading inside of the Morse Taper socket inside the main spindle.

Also worth noting:  If push sideways or up and down on the spindle I don't see any movement on my dial test indicator.

My question being: Given the advanced age of this beast, is this level of runout acceptable? Should I be happy with this? And if it not, is there anything I can do to improve this?

 

 

Edited By Ignatz on 01/06/2018 17:32:38

[IgnatzParticipant @ignatz]

[Mike PooleParticipant @mikepoole82104]

As your spindle does not move about then the runout will not be a problem for most things. A three jaw chuck always runs out but what you turn will be round. A 4 jaw independent or turning between centres will negate any spindle runout. The centre for the headstock is soft so that it can be turned in situ to compensate for any spindle runout. The socket not running true will be a problem if using tooling mounted in it but you do only have a small error. If the spindle is running without any movement in the bearings then the spindle must be worn which is difficult to correct. I think I would live with what you have but remember that it is there when it might matter.

Mike

[JohnFParticipant @johnf59703]

I am surprised that you have any perceptible runout, however it would be interesting to know if the internal / external readings are at the same point of rotation i.e. they coincide + & – at the same point.

[Neil LickfoldParticipant @neillickfold44316]

Turn a test piece, with a very fine feed rate. Then place your DTI on that turned surface and try to asses the roundness of the test piece in place on the spindle. Then cut that piece off the bar, and then place that into a vee block , and again check for roundness. It also depends on the type of the DTI being used, and the rigidity of the stand/ DTI holder as well. Then decide if the roundness of the part is acceptable for what you are trying to achieve.

Neil

[HopperParticipant @hopper]

Posted by Ignatz on 01/06/2018 17:30:14:

I've recently had reason to check the main spindle of my old ML10 modelbuilders lathe. This is one of the early models with the spindle running direct in the cast iron of the headstock casting with full loss oil drip lubrication.

I find that the measured runout on the outside of the threaded mount is about 0.01 millimeter ( = 0.0003936996 inch )…

Myford's factory inspection sheet specifies 0 to .0003" runout on the spindle, for a brand new lathe leaving the factory. Fifty or more years later, a reading of .00039" is pretty darn good if you ask me. Leave it well alone. Ditto for no discernible up and down movement of the spindle. Your spindle and bearings are in very close to as-new condition.

What was the reason you say you had to check the runout in the first place? Chatter? A strip and clean and careful reassembly of the carriage, cross slide and top slide dovetails and gibs etc might be in order every half century or so to get rid of minute swarf particles and take up any slack from wear.

Or is there some other problem that led you to suspect the spindle runout/bearings?

[SillyOldDufferModerator @sillyoldduffer]

Depending on what kit you have, accurately measuring run-out less than 0.01mm is quite a challenge. Dirt, surface imperfections, the instrument, and technique all add error. It may be that the lathe is slightly better or slightly worse than you think. Either way, it's pretty good.

I wouldn't worry about it unless the lathe is malfunctioning and – Hopper's point – you've eliminated all other sources of trouble first. For example, loose gibs and backlash are common maintenance / wear issues.

In the good old days operators didn't seem to worry about measuring their equipment. Professional lathes were periodically checked by specialists who had the necessary tools and training. Amateurs made do with what they had. Now we all have access to affordable DTI's etc it seems fashionable to check new machines out – I've done it myself.

I'm not convinced it's sensible; even in well-trained hands expensive measuring kit can mislead horribly. Bit like going on the internet with a sniffle and convincing yourself you must have Black-water Fever.

In practice, you can still get good results from 'faulty' equipment – if run-out really mattered, no-one would ever use a 3-jaw chuck. (Even a wonky chuck spins around a fixed axis, and for many jobs it's only the axis that matters.)

Nowadays I only take measurements off a machine when it doesn't cut as expected, or when resetting it. More often than not, faults are eye-ball obvious, like the top-slide backlash needs adjusting, or the tool height is shimmed wrong.

My experience is all with new kit. Are older machines that different, or are worn beds and shot bearings also eye-ball obvious?

Dave

[IgnatzParticipant @ignatz]

The reason I actually went and put a readout on the spindle was because I just purchased one of those 'cheap-n-cheerful' Chinese-made er25 thread-on collet holders for the Myford.

Now from everything I've seen on the web, I know that those collet holders are notorious for some rather loose tolerances. And indeed when I put the DTI on the internal ground area where the collet would be seated I was getting runout of something like 0.05mm…

…and that started me wondering what the accuracy of the lathe spindle, itself, was. And from all of your responses, it would seem that the lathe isn't so bad in that area.

Of course, the lathe bed, cross slide and so forth, now those areas have had a harder life… But that is for me to possibly work out at another time.

 

[Author]

Posts