Morse Taper

[Joe PageParticipant @joepage27051]

Hi,

I've never had any experience with the threaded type of morse taper sleeves, only the tung type.

My question is, what size thread drawbar would you use for a mt2 and mt3. Are they normally metric or the same thread as an R8 type.

Decided that I'm going to make a mt4.5 to mt3 sleeve for my lathe as the Harrison m250 has the annoying mt4.5 headstock, so I need to know what kind of clearance hole to drill through the sleeve so that a draw bar for the larger mt3 can pass through.

Thanks,

Joe

[Joe PageParticipant @joepage27051]

[John Stevenson 1Participant @johnstevenson1]

MT3 is usually 1/2" Whit or M12 depending on sex.

[Joe PageParticipant @joepage27051]

Thanks John, I assume it's M12 x 1.75.

[egaParticipant @ega]

5/16" and 3/8" respectively used to be normal. The last MT3 tool I bought was indeed M12 and I promptly converted it to 3/8" BSW.

[JasonBModerator @jasonb]

You can get unisex ones where the imperial sizes have metrc M12 thread, as thats what I have got, yes standard metric coarse thread.

Your sleeve will be better and easier made the length of the MT3 taper and just run the taper out the end rather than a closed end with just clearance for the drawbar

This is my MT4 to 3 adaptor and a 3/4 collet with M12 thread

 

Edited By JasonB on 05/01/2016 08:14:00

[Joe PageParticipant @joepage27051]

Decided to start making an adapter today, I instead have gone for two draw bars. A tube like one for the MT4.5 adapter and then a rod drawbar to run down the middle for the MT3 adapters. I wanted to machine the MT3 bore with the adapter inserted into the headstock, hence the reason for two drawbars. Used the CNC to get the angle right and it turned out perfect, 2000rpm, 12mm hold, 110mm over hang, 0.6mm cut really didn't feel all that safe :s.

Just got to make a nut and machine the other side, piccys:-

[Ian S CParticipant @iansc]

The 5 MT to 3 MT adapter for my lathe is just the length of a tangles 3 MT, so it will be short over all as a 5 MT taper. For the amount of use mine gets, an unhardened home made one would be ample.

Ian S C

[Neil WyattModerator @neilwyatt]

Mine are all 3/8" whit. or M12.

Neil

[MuzzerParticipant @muzzer]

Posted by Joe Page on 06/01/2016 19:56:44:

turned out perfect, 2000rpm, 12mm hold, 110mm over hang, 0.6mm cut really didn't feel all that safe :s.

Wow, you are more of a man than me – or perhaps your rubber pants are stronger. Holding on by the tips of the 3-jaw with 110mm overhang – hope you weren't standing alongside when it was cutting. That's another benefit of CNC control I suppose – you can stand outside the shed while it does the business.

Merry

[Dave plus / minus 40 thouParticipant @daveplusminus40thou]

Excellent work Joe!

you have reminded me that I should pull my finger out and make one also for my Colchester student – what are the dimensions for the MT4.5 taper?

cheers

Dave

[Tim StevensParticipant @timstevens64731]

If it helps anyone working so small, MT 2 collets come with M10 (x1.5) or 3/8 proper English Whitworth.

And the 3/8 will screw into the M10 until it jams, so check …

Regards

Tim

[Joe PageParticipant @joepage27051]

Muzzer – stood with a thick Perspex sheet in front of me with one hand and the other hand on the emergency stop, It did scare me so I haven't run it that fast since.

Dave – The taper is 1:19.2307. I started the big end a mill above the nose bore and tapered down a mill below the bore. So the big end was 39.2mm tapering down to 34mm at a length of 100mm (39.2 – (100/19.2307). I admit I'm not happy with how little contact area there is in the nose, not sure what the Colchester is like, but the Harrison M250 is only 15mm long, about a 30mm gap and then a little more of a taper.

Turns out I had a MT3 arbor for a drill chuck, has a M12 thread in back .

Anyway as for the adapter, made a nut for the draw bar from a top end timing pulley, magnesium alloy so it seems to have worked out ok because the threads aren't sticky, saved some time instead turning and milling a nut. Drilled out the adapter nose to 20mm as the smaller end of MT3 is 20mm, just to allow tung types to fit down it. Then bored it out using aluminium inserts and the final pass was 240rpm, 0.5mm at 20mm/min. The boring bar was only turning 90mm inside but had to stick it out 120mm due to the carriage hitting it's limit.

Overall I'm really happy the way it turned out, taper came out perfect and no mistakes, yeay. Piccy's:-

[Dave plus / minus 40 thouParticipant @daveplusminus40thou]

Brilliant – Thanks for the numbers Joe,

My student (1800) has the same arrangement as the M250, two bands of contact for the taper and a gap between.

Cheers

Dave

[Joe PageParticipant @joepage27051]

Hi Dave,

Forgot to mention, if you work in imperial, the "original" taper is 0.624" per foot. (or a taper ratio of 1:19.2308, not 2307, not that it makes much difference. I recorded the process on **LINK**

Regards,

Joe

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