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

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.

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

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.

On 15 September 2024 at 16:18 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

On 15 September 2024 at 17:35 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

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.

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?

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