Myfor ML7 main spindle replacement

I'm looking to swap out my 1953 ML7 spindle because of damage to the internal taper. My options are either to find a complete original spindle with bearing shells, a spindle on its own, or a new hardened spindle with bronze bearings from Myford. The last time I checked with Myford they did not have any new assemblies and in any case they were over £400 (I think plus VAT).

I wonder if I replaced the spindle on its own and kept my shells, whether there would be excessive wear as the mismatched items bed in. Maybe taking off a shim or two and scraping the shells could be an improvement.

Any thoughts?

(wrong lathe)

Edited By Ady1 on 27/09/2022 18:11:59

How serious is the taper damage?

Tracy Tools sell MT taper reamers for a whole lot less than the costs you are quoting. They will clean up burrs etc, any gouges don't matter as tooling with 2MT tapers will bridge over those. One of those could save you a great deal of work and restore socket accuracy.

Regards Brian.

Edited By Brian Wood on 27/09/2022 18:12:58

Ady: I think Myford beat him to it. The ML1-2-3-4 mostly had a MT1 taper, but as far as I know the ML7 always had MT2.

Mick: Unless the internal taper is really, really bad I would have thought it was better to reclaim it with a MT2 reamer. For normal purposes the taper doesn't need to make 100% contact, so a few scroops won't matter. It might even be possible to turn a couple of thou off the existing taper before reaming, though you might need to get inventive with your boring bar.

It certainly sounds like a lot less work and money than changing the spindle. Has anybody else ever tried this and can offer opinions?

George

Edit : Some people type faster than me!

Edited By Georgineer on 27/09/2022 18:21:07

Yes, I have used the method, that is why I recommended it

Brian

Check the spindle diameters on the outside for run out firstly in situ on the lathe. If the outside runs true it is likely that the inside has damage which may be fixed by a taper reamer. If the spindle runns out on the outside it may be possible to straighten it using a pair of V blocks and a press or a large vice. Checking it on the V blocks and a dial indicator. It is possible to grind the inside of the taper with a grinding attachment and small internal grinding wheel. Just clock a Morse taper sleeve with the compound slide to set the angle.

David

The outside does run true and apart from the taper damage everything else is fine. When the damage originally happened I bought an MT2 reamer from Tracy Tools and cleaned up the bore, but it left 0.005" runout and it's still slightly oval. The original damage was caused when I was reaming a large aluminium bronze bush - the reamer grabbed hard and got pulled into the spindle (I have a lever feed tailstock, so there's no limiting on travel like you'd have with a screw feed). By the time I'd reached for the off button the reamer had broken a flute and badly chattered the spindle, but with more damage on one side.

I contacted Myford and apart from replacing the spindle and bearings, the suggestion was to bore out the spindle parallel and fit a hardened precision ground sleeve. If I could just replace the spindle it would be much easier for me.

Bite the bullet £359.50 incl. VAT and apparently Myford have instock. Alignment and fitting second hand parts a potential nightmare.

Robert Butler

Good morning, Mick,

How about this: eBay Spindle

Best regards,

Swarf, Mostly!

Apart from hopefully securing an undamaged spindle the question of the bearing fit remains. Spindle and bearings were precision hand fitted at the factory, this option attempts to accomodate a used spindle from one lathe and bearings from the existing lathe and we must not forget the shim issue. Unless the OP has significant fitting experience and the means of acturately checking the whole spindle could be out of alignment rather than just the MT2 taper.

Robert Butler

The Ebay spindle looks to me to have evidence of being cleaned up with emery or similar - it's suspiciously free of any regular wear marks. This leads me to wonder what level of precision the spindle has, and how it would fit up. Would it be better to locate a complete assembly with bearing shells?

Does a brand new hardened spindle with bronze bearings need to be scraped? If it does then perhaps the same issues of alignment exist. I have some experience of hand fitting using engineer's blue and scraping, though in engines not lathes.

Hello Mick,

I know this sounds very much along the lines of "Bodge it and fix it" but I think it might be worth trying; after all you will still have the other alternatives open to you if it doesn't work.

If you have a 2MT drill with a poor taper fitting that you are prepared to sacrifice if necessary, try a little fine valve grinding paste on it. Run the lathe slowly and hand hold it in a glove, biasing the cutting to reduce the ovality and with it hopefully the runout. Test frequently with a test bar if you have one, having cleaned things up between runs of course!

In my early days with far less equipment and knowledge, I recovered the 2MT socket on an ML4 that had been scored with a boring bar, not by me I hasten to point out. It ran true after this work and still gripped taper tooling and the lathe went on to allow me to build my Dore-Westbury mill, still very much in use 30 years later. I sold the lathe on later, but with a clear conscience.

I feel for you, not a nice thing to recover from.

Regards Brian

Mick if you can scrape enough off bronze bushes to misalign them you aren't doing what I call scraping.Surely we are talking tenths here and the bushes are what 4 or 5 inches apart .

The only thing that ever went in the spindle taper on my ML7 was a centre for between centres turning. I always skim them in situ anyway, so as long as the damaged taper holds being eccentric doesn't matter. If it's really bad then you can just use a short bit of bar in the 3 jaw with a point turned on, just loses a bit of overall length between ctrs. I wouldn't fork out half the value of the lathe for this.

I've been using a short piece of bar in the chuck as a centre, as you recommend.

The issue for me is that collets I use for clockmaking don't run true. I can get around it with rudimentary split collets made from hex brass bar, but when filing pivots there's always the danger of rotating chuck jaws. Collets are a lot safer and easier to use. I've put up with the lathe as it stands for over 30 years and would really like to get it sorted out, but cost is a factor and I don't think I could afford to buy a new spindle assembly from Myford.

Not being familiar as to the utilisation of your collets, I assume they have to be MT2. If not ER32's and a screw on collet chuck may be a useful option.

Robert Butler

Edited By Robert Butler on 28/09/2022 19:59:25

What you need to do is BORE the tapered hole so it is concentric and round again.

Reamers will follow the existing wonky hole and cause silliness. Boring the taper is easy peasy using the topslide set at an angle. To get the right angle you set up a known good MT2 centre between centres and use a dial indicator to set the topslide to a zero-zero reading. Centre can be held between a pice of stock in the chuck with a centre drill hole drilled in it and a tailstock centre that fits in to the centre hole that most centres have in the tail end from the manufacturing process.

Or turn a piece of bar parallel and use dial indicator to set topslide at correct angle to get the correct thou offset over one inch of topslide movement. You can look up the taper per inch on charts etc. And remember to halve it.

Test your topslide angle by turning a male taper and check how it fits in your tailstock , using felt pen marks and slight rotation to get a reading. Once happy, set up a boring bar and bore out your spindle to get rid of ovality and eccentricity. There is plenty of stick out on most Myford spindle so should be enough "meat' to clean up the taper. Don't try to remove all the gouge marks. Just make a round concentric hole that will grip your collets. You could finish the hole of with one or two turns by hand of your reamer if you wish.

Otherwise, you will have to scrape your old bearings to fit any new/used spindle. Which is much harder to do than a simple boring job.

I rebored the trashed taper on my ML7 using the second method I described - parallel turned bar and dial gauge -- and it worked perfectly.

Would that not be the reverse for boring the taper?

Anyhow, I think this is the best way to rescue the taper in the absence of a toolpost grinder I have a very rigid boring bar that should do the job and could always lap the bore afterwards for a fine finish (must remember to turn up an aluminium lap with the same topslide setting).

Lapping tapered bores is fraught with difficulties and it's far too easy to end up with a load of concentric grooves rather than a nice smooth bore. With a parallel bore you can move the lap axially to distribute the medium; with a taper you're scuppered.

Hopper's suggestion of boring it is one I would go for if I was in the same position as Mick Bailey. Good luck with it, Mick, whatever course you end up taking.

Hoppers method would be the way I would tackle it, but if you are wary of trying to machine the spindle yourself you could get Spindle Services of coventry to re-grind the internal morse taper. They are very helpful and reasonably priced I had the spindle assembly of a Hayes Diemaster straightened, re built, and reground with new bearings at a very reasonable price not that much more than I could have bought the rather rare and costly bearings. If you are willing to let them fit it in between other jobs they will accomodate us amateurs quite happily.

Much , much less than the cost of a new spindle or even a used one from ebay.

Good luck with whatever you decide.

Dave

I always offer cash for any such work, sometimes it helps!

Edited By Dave Wootton on 30/09/2022 13:29:49

Edited By Dave Wootton on 30/09/2022 13:30:51