ML7 spindle change

[Mick BaileyParticipant @mickbailey28509]

My white metal bearing shells are in nice condition but the spindle has a damaged taper and I’m thinking of just replacing the spindle as most bearings I’ve seen are in worse condition than my own. Other than fitting up the spindle to the existing shells, is there any other consideration? This is assuming I can find a spindle in good enough condition.

[Brian WoodParticipant @brianwood45127]

Mick, you say the taper is damaged, this is of course the internal MT 2 taper. Is the damage severe and beyond rescue with a MT 2 reamer?

If the scarring is just raised bits the reamer will clean those off and leave the taper bore in working order. You can check the run out performance  after treatment with a good quality MT 2 drill or reamer, or a test bar if you have one. It might in the end be a better option for you as the white metal bearing shells are still serviceable and have run in with that shaft in place.

Regards   Brian

 

[Mick BaileyParticipant @mickbailey28509]

The damage is quite severe with considerable runout even after reaming. An MT2 test bar visibly rotates off-centre so I didn’t even measure what it actually is. I did post here a while back about restoring the taper and really the only option was to either have the spindle reconditioned by a specialist company or boring it oversize and fitting an insert which is then bored and ground in-situ. I was thinking that changing the spindle may be the least effort.

[DC31kParticipant @dc31k]

Coming at this from a purely practical perspective, we could ask how often do you really need the internal spindle taper?

One of these, held in an ER32 chuck or dialled in a four jaw, would probably do for 99% of those times:

https://www.rdgtools.co.uk/acatalog/2MT—20mm-Socket-Sleeve—Capstan-Socket-2965898.html

It would be educational to come up with a situation and frequency where this would not suffice.

The one shown is over-long, to accommodate the tang on and ejector drift for a MT2 drill, but could easily be reduced in length.

It is, of course, always good to have a machine working as intended by the manufacturer, but I mention the above just in case its present condition is stopping you doing something.

[Tony Pratt 1Participant @tonypratt1]

Nice to have a pristine lathe spindle taper but in practice you should insert a soft centre and machine it concentric for the job in hand every time. The choice is yours. 🙂

Tony

[Brian WoodParticipant @brianwood45127]

Hello again Mick,

Now that you have added to the story I suspect you have little to lose so I suggest a radical and even sacrilegious approach.

You may have a tool with a poor taper that you are willing to sacrifice the taper end of. You might even prefer to make one for this job. Make a holder for the body that you can split lengthwise and grip in the cross slide tool holder and align it as best you can with the bore of the headstock. Apply some fine valve grinding paste to the taper and use that to gently reform the spindle taper with the ‘tool’  held slightly off centre so that grinding is to one side of spindle centreline.

Proceed until your test bar shows improvement . Follow up with the MT reamer.

I can’t promise this works but on the basis that it is either muck or nettles at this stage it may just save the day

Best of luck   Brian

[Mick BaileyParticipant @mickbailey28509]

The reason for wanting a good taper is to use my existing collets for clockmaking. I’ve got by for many years with either hexagon split collets in the three jaw or using a small four jaw. The collets are much easier to use, as for many operations the chuck jaws get in the way. There’s just a better overall feel with a collet mounted directly in the spindle.

Because of previous attempts to correct the damage by reaming, the taper is now too large to hold Myford collets and already they will not close enough to grip. Any further correction would still mean the lathe qould be unsuitable fir collet use.

[HopperParticipant @hopper]

What is wrong with boring the taper in situ????

It’s very simple to do, even for a beginner. Get your self a nice insert boring bar and set the topslide do the correct angle and away you go. No big deal at all. You dont have to remove every scar from it, just enough so it works and grips.

Topslide can be set at the correct angle quite easily with a dial indicator. Either set a MT2 tailstock centre between the tailstock  and a piece of bar turned to a point in the chuck and clock it with the dial indicatior, or turn a piece of bar parallel between the chuck and tailstock, then use the dial indicator to read the number of thou over exacly one inch of movement of the topslide as per the graduated handwheel dial. (yes yes there is a very slight error because of the angle, but it is only about one thou over that distance and in practice makes no difference, in my experience.)

Reboring it will get the hole concentric again, whereas a reamer just follows the old dodgy hole.

I had to do this on my ML7. It had been butchered with a large hole being drilled down the first half of the taper as rough as guts for some reason. So I bored it out parallel for that first half, then made up and inserted a sleeve, which I then bored out tapered until it met the taper in the existing hole and cleaned it all up in one cut. Finished the last thou with a reamer just for a nice smooth finish.

And guess what? In the 7 years since, I have never once needed to use that tapered hole. On the Myford you can’t really use a soft centre straight in the spindle because then the carriage has to hang off the end of the bed into the gap to get the tool that close to the spindle. Or the topslide has to be extended out to a ridiculous level. I instead hold a piece of scrap bar in the chuck, turn a point on it and use a driving dog that engages with a chuck jaw. Much betterer.

I definitely would not even think about a new spindle just because that taper is dodgy. Just use as is, or rebore it.

Plus if you get a new spindle you really should scrape in the white metal bearings to match it. Which is not a beginner level task.

Plus plus, be wary of trusting runout on a ground test bar. Some of them are very poorly made and not to be trusted at all. Best to make your own, turned between centres on the lathe so you know its good. Or put your ground test bar between centres in the lathe and check it along the taper and the parallel section for zero runout when rotated with a dial indicator on it.

EDIT: HAHA, you posted the answer to my question as I was typing. You might consider than drilling and boring the spindle out parallel and pressing/Loctiting in a sleeve that is then finish bored, much as I did with mine.

 

[JohnFParticipant @johnf59703]

Mick, I would go for your earlier post with the option to bore out and sleeve the spindle using high strength Loctite then bore the MT in situ using a taper turning attachment if you have one or the compound slide if not.

Once you get close to the finished size you could use a reamer to finish but boring to size will ensure the best accuracy.

John

PS where are you located ?

 

[Mick BaileyParticipant @mickbailey28509]

I’m in N Staffs. Parallel boring for an insert and Loctite seems to be the best way, then bore the taper. I’m also wondering if the hardened and ground sleeve previously mentioned would be concentric enough if lightly press-fitted/Loctited. A hardened taper would seem to be an improvement.

[Mick Bailey]

On Mick Bailey Said:

I’m also wondering if the hardened and ground sleeve previously mentioned would be concentric enough if lightly press-fitted/Loctited

They also do a 2MT 3/4″ OD, which leaves more meat on the spindle.

Where have you got the idea that the item is hardened and ground?

Even if you buy one that is way out of concentric, it is far easier to make the OD concentric with the ID than the other way around. Chuck up a 2MT drill, with male taper sticking outwards. Dial it in concentric. Put the sleeve onto it and skim the OD concentric with the ID. Bore spindle to suit.

Are your collets drawbar-type or the Myford-special that use a nosecap? In either case, you could make something that screws onto the spindle nose that would accept the collet. If it were a 2-piece item, you could dial it in concentric and then pin the two halves together so they stay concentric forever. The nosecap would be used on the new item or a longer drawbar with the other type of collet.

[Mick BaileyParticipant @mickbailey28509]

I’d assumed it was hardened and ground from the previous one I bought to make a light milling spindle. It was too hard to cut with a hacksaw. I mounted it directly on a pair of taper roller races and it worked fine, though I never checked the accuracy.

They are the short Myford nose cap collets.

[Mark RandParticipant @markrand96270]

The white metal bearing’d spindles were unhardened. The later, hardened spindles used phosphor bronze bearing shells. If you want a project (not too difficult), you could make an entirely new spindle out of a piece of EN24T or EN16T and turn it with the existing spindle. To guarantee concentricity, turn the outside dimensions between centres using a soft centre in the headstock that you have turned a true 60° on with it in place, keeping it there throughout the work. The internal features (and even chuck mounting and threading) can be done with it mounted in the headstock.

Sounds like a scary proposition, but I did a major rebuild of a Hardinge HLV lathe using the ML7 to make all the apron gears and shafts.

It is a shame that Myford/RDG haven’t seen any value in making spare spindles and bearings.

[Mark Rand]

On Mark Rand Said:

……………………..

It is a shame that Myford/RDG haven’t seen any value in making spare spindles and bearings.

They have, but currently out of stock, though the price may be prohibitive.
https://www.myford.co.uk/product/b24-b25-b32-ml7-headstock-spindle-and-bearing-kit-complete/

Bill

[Michael GilliganParticipant @michaelgilligan61133]

Am I permitted to be slightly confused ?

.

.

[ perhaps they mean “… will, in the fullness of time … ]

… Academic interest only, as mine is an ML7R

MichaelG.

[Michael Gilligan]

On Michael Gilligan Said:

Am I permitted to be slightly confused ?

.

.

[ perhaps they mean “… will, in the fullness of time … ]

… Academic interest only, as mine is an ML7R

MichaelG.

I can only guess that they mean the outer of the bearing sleeves will need fitting to the lathe headstock.
On the other hand it could be leftover text they forgot delete when they updated the spindle set.
Bill

[Neil LickfoldParticipant @neillickfold44316]

There is about 3mm to 4mm of movement and a #2 MT is fine. You can take out 0.1mm in diameter and it will shift the taper about 2mm. Roughly 0.05mm per 1 mm length.

Bore in situ is the best option.

[Mick BaileyParticipant @mickbailey28509]

To be clear, I was referring to the capstan sleeves being hardened and ground – I know the ML7 spindles are unhardened.

The apparently contradictory advice given by Myford about scraping the bronze shells also had me confused. Tony Griffiths never mentioned anything about scraping when he described fitting them to his own lathe. I did consider buying a new spindle the last time these were available, but It didn’t make economic sense to me.

If the RDG sleeves are now unhardened one could be turned down below 3/4″ to reduce the amount that would need to be bored from the lathe headstock. Maybe though in the end the best concentricity would be had by using a plain Loctited insert with the taper machined in-situ, as already suggested. Given the existing state of the bore there’s nothing to lose.

Making a new spindle seems to be a lot of effort to go to, given the fairly decent spindles come up for sale quite regularly – sometimes with good shells.

 

 

[Andrew CrowParticipant @andrewcrow91475]

Hi Mick,

I’ve just sent you a pm if you’re interested get back to me.

Andy.

[HopperParticipant @hopper]

A quick phone call to Myford should clarify the scraping issue. They are generally very helpful.

If the bronze bearings are a bored finish and not ground, they could well use a final scrape in to get best finish and fit. That is pretty normal on bronze bushings on larger machinery if precision is required. They may also require a bit of relief scraping in along the join lines between the two halves to act as an oil reservoir to aid the hydrodynamics where the spindle rotation forces oil into the gap around the bearing.

[noel shelleyParticipant @noelshelley55608]

Plan B, there is a 2 piece ER32 collet chuck that fits the Myford spindle nose thread. Being 2 piece means it can be dialled in to truth. this may be both cheaper and even better?  Noel.

[HopperParticipant @hopper]

ER chuck is certainly worth considering. Boring out the spindle to the diameter of the large end of MT2 plus wall thickness of a sleeve could weaken the spindle nose and lose stiffness.

John Stevenson did suggest, when I posted about my messed up spindle taper way back, boring out the end of the spindle to take ER collets and make a ER nut that screwed onto the Myford spindle nose thread. I dont remember what size ER collets were mooted. Maybe ER11 or 16 or so?

[duncan webster 1Participant @duncanwebster1]

If one had an otherwise good spindle but with damaged bearing seats it could be recovered by hard chrome plating and grinding back to size. Then you could use leaded bronze bearings. Whether this is cheaper than a new spindle l don’t know

[Neil LickfoldParticipant @neillickfold44316]

A 12mm shank CCGT carbide bore bar will recut the spindle inner taper. It is a great bar for general boring as well.

[JasonBModerator @jasonb]

i’d stick a 5C chuck on it for collet work.

You can hold short work better than with an ER. Bigger range of sizes than the Myford Collets or ER plus options for Square and Hex. Nicer and safer to work up close to with hand tools like gravers than an ER or the Myford closing nut. Single key operation not two spanners. No mucking about with the existing spindle.

 

Sell the Myford collets and nut and that will cover the cost of a 5C chuck, backplate and a large number of collets.

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