Machining a female MT1 taper

I've been asked to make a spindle with an internal MT1 taper. I'm pretty sure that I can do it, at last resort by trial and and error with a slender boring tool, but it's a challenge because MT1 is only ~ 9.4 mm at the thin end and about 54mm deep. It'd take a long time and much blue (Stuarts and language) I expect.

Looking for an alternative approach I came across these reamers:

The top one is 'roughing' and the other finishing. But I don't know how they are meant to be used. Could I get away with step drilling or boring, then use the rougher to take off the corners and finish with the other? They are cheap Oriental offerings made from carbon, not HS, steel, but it's a one-off in EN1A so maybe it could work.

Has anyone used these tools and can advise? Or any suggestions for other methods?

Robin.

Edited By Robin Graham on 12/05/2021 02:17:04

Edited By Robin Graham on 12/05/2021 02:22:13

Robin

i make a few mt 2 sockets and use just the finishing one

i drill down the smaller diameter and then perhaps halfway with the middle diameter.

hold the reamer in the drill chuck and at perhaps 500 rpm advance the reamer and cut just a couple of mm

retract and clean the flutes apply cutting oil liberally and repeat until its cutting all it length.

Cutting a reamed taper is only slightly more demanding than a parallel reamed hole for anyone with reasonable ability - I can do it!

The trickier part is making sure the cone is exactly along the desired axis. Trial and error can become expensive, even when using reamers - materials and cutters (in carbon steel).

For this reason, you are probably better off boring the hole tapered as best you can before using the reamer to finish the job. As with reaming parallel holes, drilling is the roughing operation but is not necessarily concentric, then boring the hole establishes concentricity and location, then reaming finishes the hole off to final size and surface finish.

And a lot of spindles don't use the full length of the MT1 reamer but stop a bit short, so a slightly larger diameter at the small end makes life a bit easier for boring bars etc. Take a look at some MT1 drill bits and centres etc and see how small they actually go down and maybe aim for just a bit under that?

We use these at work to produce 4MT holes in graphite components & used similar form taper pin reamers at my previous employment.

Just drilled a bit larger than the small end diameter of the roughing reamer to start. The roughing reamer requires retracting frequently to clear chip build up & we used Rocol RTD liquid as a lubricant for the taper pin reamers into steel or CI (dry for graphite). Leave a small amount to clean up to size with the finishing reamer.

My recollection of using the taper pin reamers is that the rougher took a suprisingly long time to clear out the hole before a few turns of the finisher get a good finish. IIRC we used a magnetic base drill to both drill and rough ream, then finished by hand.

The graphite components were produced on a vertical machining centre & were only around 40mm thick, so were quite quick to machine - still needed to retract the roughing reamer frequently to clear the flutes & prevent clogging. Graphite is abrasive though & the HSS reamers needed sending out for regrinding after every batch of components.

Nigel B.

I scribed a line on my cross slide with my topslide once I got things set up and use it if I ever need an MT1

Make sure your boring tool can go "all the way"

Don't overcut the hole entrance, big no-no

Test with an MT1 often

Use the reamer to finish off

GL

Hi,

The two things that are important when making an internal morse taper are the
fit of the the taper and the axial alignment within the spindle ,step drilling
or boring and then reaming is less likely for this to be so .It is a simple
job to make a solid boring bar to cut these tapers ,the 2 here in the photo
are made just as morse taper for making 1 and 2 morse tapers but
undersize to allow the toolbit to protrude ,as such the boring bar will
be strong enough to not deflect and small enough to clear the small end.
When making these sort of spindles i find it easier to do the morse taper first
and use a double ended morse taper arbor and mount the job on this to cut
the outside parts of the spindle.
These days i leave enough in the taper to finish grind the taper mounted in
the spindle bearings , just because i can, seen here in the photo grinding
a 1 morse taper , the last 2 mt one that i had done was better than the
Myford 7 spindle nose and they are pretty good in any case.

John

Couple of photos I posted that may be helpful when you've made the socket and want to turn the outside concentric. I wanted to make an MT2 ball bearing spindle and had a bit of bar with a socket already cut. So I made a double-ended MT2 arbor, shown to the right. on the left is the complete spindle with an M2 blank end arbor in the socket.

When it comes to turning the spindle I put one end of the arbor in the headstock with a drawbar and the taper in the spindle on the other end with another drawbar.

Then I could carefully turn the spindle OD concentric with the socket. If your spindle isn't too long you might do something similar?

Thanks for replies. Obviously many ways to skin this cat - sadly I won't be able to use John Pace's grinding technique because - well, I can't. Looks like a nice way if you've got the kit though! The idea of a making Morse taper boring bar is interesting - I could probably do that.

I've now bought the tools pictured in my opening post though (only one remaining, order within 39 minutes for next day delivery - I'm a sucker for that sort of sales pressure) so shall experiment with them bearing in mind advice about achieving concentricity.

I'm sure I can make the spindle to acceptable tolerances one way or another, but I'm going through a 'get it right first time man' phase. I'm bad at planning lathe machining sequences to avoid resetting the work, losing concentricity and having to resort to the 4-jaw though.

This is the spindle I want to reproduce:

The internal 1MT taper is on the left - the rest of the spindle is solid. My thinkings so far, based on the kit
I have are:

1. Mount an oversized bar between centres, turn the external features then remount on-axis in the 4-jaw to make the taper.
2. Make the taper first in oversized bar, put a small 60 degree chamfer at the end, mount between centres and then do the external features.
3. Make the taper in oversize bar first, bung in a 1MT soft arbor and rely on the centre hole in the soft end of the arbor to turn the external features between centres.
4. None of the above

It's for a wood turning lathe, so a couple of thou out isn't going to be a problem, but I want to get it as accurate as I possibly can - I took the job on for a small, but negative, financial gain as a way of advancing my skills and doing someone else a bit of good.

Robin.

Edited By Robin Graham on 14/05/2021 01:18:58

Edited By Robin Graham on 14/05/2021 01:27:37

Edited By Robin Graham on 14/05/2021 01:36:01

My engineering know-how is limited, so my initial thought of how I would attack the job is:

Sort out the morse taper in an over-sized bar, as concentric as possible.

Use a commercial MT1 blank ended arbor as a fitted support for the bar and machine the bar parallel to its morse taper.

Likely the parallel arbor might be set up on the lathe, in a collet chuck, and (eventually) the far end would be supported by a centre. It might involve turning between centres as these blank ended arbors are fairly useful in that respect.

Another thought would be to press one of These into use, if I had one... 4 jaw chuck to line everything up and go from there.

Hi Robin,

Seeing your last post , this illustration may be of some use it is not
often seen now days but is a viable method to retain some concentricity.
They show this here as you have described reaming the internal morse
taper ,i would have thought that it would be wise at least to pre bore the
hole to as near morse taper form before using the reamer.
The sequence is much the same as you have described except for
the mounting in a 4 jaw chuck.

The set up is to turn between centres ,fit and adjust the fixed steady
whilst still held on centres,remove the tailstock away ,retain the
part on the headstock centre with the spring dog.

When you say the shaft is solid,is there no through hole ,if so how
do you eject the centre?

John

I think I'd keep it simple and use option 1.

Might be different if it were a precision grinder spindle and we were working to a tenth of a thou. But for a wood lathe spindle, and providing your four jaw chuck is in good condition, option 1 should work ok. A bit of patience with the four jaw and you should be able to set it up to zero runout or within a couple tenths of a thou, before drilling, boring and reaming the internal taper.

Be very careful with the final fitting of the taper. They can disappear down the hole rather quickly at the end. A very small increase in diameter can translate into a surprising amount of lateral movement. Maybe have practice on a bit of scrap to get a feel for achieving the final fit.

Thanks for further suggestions. I think I now have enough to be going on with with - I have plenty of 1" scrap to play with, so shall try various things in the hope that when I get to the job proper I'll have a rational 'schedule of operations' (I've learned some new vocab there!) worked out and get it right in one go.

NDIY - I am planning to buy a MT1 soft arbor if only to line up the topslide for initial boring (I don't have any MT1 tooling) , so good to hear that you have found they can be useful for between centres work.

John - many thanks for the illustration and accompanying text. That's very useful. Can you give a reference? I want to see Fig 28! And where does the universal grinding machine (I haven't got one) come into the story I wonder?

The manufacturer (Nu-Tool) of the lathe supplied a nut to fit on the threaded nose of the spindle - the idea being that unscrewing the nut will eject the centre. I don't understand why they also made the spindle hollow, but I could drill it through if there is good reason.

Hopper - you are right - for a woodworking lathe it's not worth chasing tenths. But maybe someday I'll want to make a precision spindle or a precision something else, and this experience will be useful. So I want to get it as good as I can. I take your point about the centre disappearing down the hole - I shall tread softly.

Robin.

I've used reamers to finish machine Morse tapers but its never been completely successful. I can detect very small errors, that is to say a run out, something in the order of a thou or so. I think this happens because the reamer tends to go where it wants rather than follow the pre-bored hole. Also its a very long cut, inconsistencies in the condition of the cutting edges must have some effect. Having said that the taper is spot on, grips really well.

What I do to ensure absolute accuracy is to bore and ream the taper then finish the other diameters by mounting the work piece on a suitably tapered mandrel that has been machined and not removed from the lathe.

I would agree wit John P. finishing the taper by rotating the shaft on its own bearings is the best way, absolute accuracy comes easily then. The attached photo shows a 4MT taper being finished machined while the shaft spins on its own bearings mounted in the quill of the machine it is going to be used on. (The two fixed steadies are gripping the quill so it cannot rotate)>

Hi Robin,
I've copied the whole of the illustration here and it shows the complete
sequence of operations , these copies come from a re-print of a book
from the 1920's and as such the working methods reflect that era , much
of this is still relevant in home workshops today ,with that in mind the shaft
depicted would most likely be hardened to run in plain bushings and need grinding ,the second
print here shows a similar shaft set up to have the internal taper ground using
this time belt lace to hold the shaft against the headstock centre.

The third photo here shows a similar set up using a sprung dog holding
the shaft on the headstock centre ,just for reference the springs have
about 15 to 20 lbs tension in each one.

No universal grinding machine about the only chance these day of owning
such a thing is to build it yourself ,unless you are lucky to find an old one
to restore ,don't think they are made these days.

John

Many thanks for taking the time to post those pics John - much appreciated. Often I am either confused by technical explanations (too hard) or frustrated by over simplifications (too soft), but the level of the text you reproduced is pure Goldilocks for me. Obviously I'm 100 years behind the times.

It turns out that the spindle in question was knackered by an over-enthusiastic attempt to remove the original bearings, and the damage is limited to the threaded portion to the left of the flange in my earlier pic. In which case I might be able to fix it without having to make a new spindle. Shucks, I was looking forward to the challenge. I might have to do it anyway, just because I think I can.

Robin.

Edited By Robin Graham on 16/05/2021 23:25:34

Just to wind up with how it went. The repair didn't work (the spindle was too badly bent) so I reverted to plan A.

I set up to turn between centres:

and turned the outboard LH thread and other external features. I was pretty happy to find that (according to my Sunday Best Mtitutoyo mic) the parallel section was indeed parallel to 0.002mm over 100mm.

Because I had no easy way of doing the spring-loaded dog thing, I turned the work round, set it in the 4-jaw and centered on the bearing seats by fiddling with the chuck and the steady arms:

I then parted off the stub at the tailstock end (yes, I did take the tailstock off before finishing the cut), drilled, bored and reamed the internal taper and cut the RH thread with this setup.

The finished spindle:

has ~ 0.01mm TIR on the internal taper with respect the the bearing seats. OK, not great but not too bad.

I nearly had a heart attack when I spun up the (commercial) drive centre and saw the spur point wobbling visibly - but it turned out the commercial part was at fault. I guess it really doesn't matter so much with woodturning,

Many thanks for advice - I've learned a lot from this project, simple as it may seem to many of you.

Robin.

Edited By Robin Graham on 30/05/2021 00:13:13