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Cleaning Internal Morse Tapers

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Dr_GMJN04/11/2020 17:51:31
1266 forum posts

I'm guessing the old hands will be shaking their heads at my novice questions here, but still...

I'm still fettling the lathe ready for the next job; now on to the ML7's head and tailstock tapers: Mine are a bit "flaky". I doubt they've had much attention in the past few decades. Nothing major, just a bit pitted and tired looking inside. I cleaned them with some Scotchbrite, and applied some blue to a centre to see what the contact is like. It's a bit difficult to tell, but it looks like after rotating the centre in the hole, there's a band about 3/4" wide that has the blue removed, closer to the wide end. There are a couple of rings visible towards the end of the tailstcok socket, but they feel scored rather than raised.

I looked online, but couldn't find anything definitive on how to assess a morse taper.

Is there anything I can do to tidy them up a bit - I'm not 100% confident they're that good, and at the very least they look a bit shabby. I don't particulrly want to ream or mchine them if I can possibly avoid it. Tools dont slip in them, it's more accuracy I'm concerned with.

Steviegtr04/11/2020 18:06:42
2420 forum posts
336 photos

What about valve grinding paste in an old morse taper with enough stick out to rotate the taper back & forth like grinding a car engine valve. Then a good clean out. At least that would not alter the taper dimensions.


Dr_GMJN04/11/2020 18:12:55
1266 forum posts
Posted by Steviegtr on 04/11/2020 18:06:42:

What about valve grinding paste in an old morse taper with enough stick out to rotate the taper back & forth like grinding a car engine valve. Then a good clean out. At least that would not alter the taper dimensions.


Maybe, although it would have to be a known good male taper I guess.

Ive also got some SiC powder, #600 and #1000, but getting rid of it afterwards might be an issue.


Vic04/11/2020 18:23:49
3060 forum posts
8 photos

One of these?


Thomas Cooksley04/11/2020 19:27:57
55 forum posts

Hi Doc, I know you said that you didn't want to ream the head and tail stocks but I am afraid I agree with Vic a morse taper reamer is going to give you the best finish and pay dividends in the long run. Tom.

Dave Halford04/11/2020 19:29:13
2001 forum posts
23 photos

The trouble is if you can rotate a taper to leave witness marks in 'blue' then it's not seated and wont tell you the truth.

If you can get two centres to align vertically then it's fine. If they don't, tighten the tail spindle clamp properly (I got caught with that one.)

If you can use a 3/8 drill in the tail that doesn't slip then it's fine.

old mart04/11/2020 19:43:12
3717 forum posts
233 photos

Valve grinding paste is too coarse, even the fine, the taper reamer with a little oil is a better bet, just a bit at a time and using the blue until 90% clean up is shown. The test should be carried out with more than one MT in perfect condition and the average taken.

IanT04/11/2020 20:25:04
1983 forum posts
211 photos

Having a few old machines, I've dealt with several MT2 taper sockets that were slightly damaged, probably by using tools with damaged tapers that were then 'spun' in the socket. Morse taper drills are probably the main culprit and I don't think it's uncommon. I've also managed to embed something hard in a headstock taper that wouldn't just brush or wipe out (I was first alerted by a scratch mark on a soft taper tool).

In all cases I've used a MT2 taper reamer - but not as a full on reamer. I've just inserted and gently twisted the reamer into the taper enough to remove any burrs or muck that was causing the problems. My Warco 12-speed drill press used to drop it's chuck quite regularly until it was cleaned in this manner. I didn't apply any great pressure when doing this operation but on removal, there was definitely a very small amount of metal/muck sat in the reamer flutes.

Your tapers may be more badly damaged than mine were but this is an in-between solution that has worked for me in the past. Otherwise you may have to actually fully ream and remove much more metal or simply replace the parts.




Edited By IanT on 04/11/2020 20:29:15

Dr_GMJN04/11/2020 22:37:04
1266 forum posts

Thanks all.

To be honest I’ve never had any issues with them, and they appear to line up spot-on (tail and headstock), it’s just that doubt that the chuck or centre or whatever is actually fully seated, the doubt coming mainly from their appearance, but also that the blue certainly wasn’t uniform. If I hadn’t turned them I guess it could be worse, ie I’ve smudged a couple of contact patches into a ring.

Predumably with the reamer I’d use it with a centre in the headstock, and then same in the tailstock, in both cases turning with a tap wrench or spanner? And just a clean up rather than any real cutting of the conical surfaces for starters?

And to evaluate, coat the male taper with blue, push in, then straight out and inspect?


IanT04/11/2020 22:47:22
1983 forum posts
211 photos

If you try my suggestion, then I just let the reamer seat itself - holding it manually...



Mike Poole04/11/2020 22:48:15
3299 forum posts
73 photos

I would tend to go with a morse taper reamer if a spindle is not too hard, a hardened spindle is not going to do a reamer much good. If a morse socket is not harder or as hard as the reamer then a clean up of any damage or corrosion should make a worthwhile improvement to the socket. A light clean is unlikely to impair the truth of the socket as you will only be clearing any imperfections. Of course you will need to check the hardness of the socket and buy or borrow a reamer. If the socket is hard then grinding is the only solution, lapping is not going to be easy I would think and the random application of abrasive could make things worse.


Ady104/11/2020 23:02:32
5063 forum posts
734 photos

I've made quite a few mt1 tapers and a reamer for finishing off is essential

You can always polish it off with a bit of paste and an ok male taper but to get-it-right a reamer I have found is essential, so much so that I got a second spare one

They remove very little material but it doesn't take much at all to make a taper not quite right into a snug as a bug taper


Edited By Ady1 on 04/11/2020 23:03:57

Hopper05/11/2020 00:44:43
6180 forum posts
319 photos

Dont use liquid engineer's blue to test a morse taper. It is a thick, gloopy (to use the technical term) liquid so it flows all over the place under pressure and gives all kinds of false readings.

The traditional method was to draw longitudinal pencil lines along the male taper all round it. In today's modern hi tech world we use felt pen. Then insert into socket and give it a slight turn back and forth, a quarter or eighth of turn or so. Then look where the pen lines have been removed. Those are the high spots.

If you put grinding paste in there and rotate etc, it will remove as much metal from the male taper as it does from the female. So those two particular tapers will end up matching each other nicely. Then your next, pristine male taper will not fit so well because it has not had the same spots ground down by paste.

So best to use a reamer, but judiciously, and return the taper to a standard format. Myford tailstock is not hardened.

You'll find a lot of this ancient craft knowledge in the old books by the likes of LH Sparey but not so much on the internet. There is so much noise there its often hard to find the signal.

That said, if your taper holds firm enough to drill holes without the chuck taper slipping, you are probably best to leave well alone. Note the taper will need firmly seating either by slamming it home or a light tap with brass hammer. That is normal.

Edited By Hopper on 05/11/2020 00:45:22

Bo'sun05/11/2020 08:27:29
602 forum posts
2 photos

Not sure if I'm imagining it, but some while ago I seem to recall seeing MT's with abrasive strips to clean (not re-form) morse taper sockets.

Dr_GMJN05/11/2020 09:20:08
1266 forum posts

Thanks all.

Hopper - I’ve got Sparrey’s lathe book, but can’t find much specific to fettling morse tapers.

I wasn’t using liquid blue, it’s a thick paste that you wipe on the surface in a very thin translucent layer.

I’ve got an old Thor hammer, so I usually tap whatever goes into the taper with the leather end. To remove I’ve got a thick dowel with a copper pipe cap glued on one end. A sharp tap on that with the copper side of the hammer removes things easily.

I’ve treated myself to a pair of new Myford centres (surprisingly cheap at under £10 - maybe they made a mistake!), one hard, one soft. I’ve done some light cleaning of the cores with scotchbrite. I’ll do the between centres test and if that’s ok I’ll leave it at that. I’m conscious that once material has gone, you can’t easily put it back...

SillyOldDuffer05/11/2020 09:40:21
8461 forum posts
1882 photos

My mum, who likes everything to be spick and span, once got a shock by cleaning fluff out of a round-pin mains socket with a hair pin! Love her dearly, but she is a bit of a fuss-pot.

My advice, if it ain't bust don't fix it!

Here we have a venerable Myford in good working condition with a grubby internal taper. So what? It's in the nature of tapers to get scratched and the damage doesn't matter unless it affects grip or alignment. Grip and alignment are important, the cosmetic appearance of an internal taper isn't.

Well-meaning owners who 'improve' machine tools with unwise modifications can do more damage than good. To work, tapers have to be accurately angled so the male and female engage to the maximum. If a taper is cleaned aggressively there's a good chance of altering the angle over part of the taper such that the grip is weakened. Worse, a bodged attempt to reform the taper could destroy the alignment as well as reducing engagement. Beware of good looking second-hand lathes in case they've been 'got at'.

Keep tapers clean, otherwise leave alone until fair wear and tear requires action. As always my advice can be ignored if the owners hobby includes beautifying his workshop. (This is entirely respectable.) I don't care much about appearances, and many find my approach to tools positively annoying. Fortunately, whatever you do in your workshop, it's not necessary to please me!





Edited By SillyOldDuffer on 05/11/2020 09:41:17

mgnbuk05/11/2020 09:53:01
1175 forum posts
71 photos

Not sure if I'm imagining it, but some while ago I seem to recall seeing MT's with abrasive strips to clean

There are commercial Morse taper socket cleaners available comprising hard felt strips glued to a tapered wooden dowel. Maybe it was these you saw ? Like these.

Nigel B.

Bo'sun05/11/2020 10:22:11
602 forum posts
2 photos

Thanks Nigel, that's probably what I saw. They are very reasonably priced compared to some I've come across from Kennedy.

mgnbuk05/11/2020 10:29:00
1175 forum posts
71 photos

They are very reasonably priced compared to some I've come across from Kennedy.

Yes, the Kennedy branded versions from Cromwell are a bit eye-watering. They are slightly cheaper from Zoro (with the ongoing rather bizzare internal competition between the two) , but still a lot more than the link.

There are also files for 3D MT printed cleaners to a different design (like a plastic helical flute reamer) on Thingiverse - I have one design downloaded, but not got around to printing it off yet.

Oh, and another vote for improving the lathe sockets with a light touch of a reamer - worked for me in the past on a 3MT RF30 mill spindle.

Nigel B.

Dr_GMJN05/11/2020 10:55:28
1266 forum posts

Thanks all. As a compromise I might try one of the tapered "soft" cleaners. I think that sould get rid of any accumulated debris more effectively than scotchbrite and my finger, and it won't remove any metal.

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