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MT4 to MT3

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Peter Love 101/04/2016 14:53:58
12 forum posts
2 photos

Most likely a very daft question but here goes, I have a MT3 mill, I also have a large collection of 1 inch mill bits and an MT4 holder for them, the steel on the MT4 as one would expect is pretty hard, however, on testing I can mark it with a file, is it possible to machine the MT4 holder down to MT3 as I have not seen an upside down converter ?.

Peter

daveb01/04/2016 15:31:24
609 forum posts
10 photos

It may be possible to machine the taper, depends on how hard it is, carbide tipped tool would probably be best. Jump up taper adapters do exist but not so common in this size now and would use up a lot of headroom. You don't say what sort of holder it is but a draw bar would be essential. You should be able to find an MT3 collet chuck for a reasonable price.

Raymond Anderson01/04/2016 15:37:41
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723 forum posts
140 photos

Peter, You can get MT sleeves that step up, not only ones that step down.. Porta And Dormer are two manufacturers and there will no doubt be others. Any good engineering tool supplier should have.[ maybe not as a stock item] but will order.

Raymond Anderson01/04/2016 15:46:28
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723 forum posts
140 photos

Just noticed, If it is only to reduce the mill spindle from MT4 to MT3 then you only need a plain Reducer [sleeve ] How are the end mills held to prevent them from coming loose, are the threaded for a drawbar if so, then that will be the first end mills that I have heard of like that or do they have a tang ? if so what prevents them from coming loose ? Or is it a proper MT4 Shank chuck that you have.

Raymond Anderson01/04/2016 15:57:40
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723 forum posts
140 photos

Am with you now, Yes, you do get step up sleeves from MT3 to MT4 but you would need one that is open [through the MT3 until the MT4 ] so that you can hold both the chuck AND the sleeve with a drawbar. Thats going to result in the end mill being a long way out from the spindle nose.

Nick_G01/04/2016 16:03:06
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1808 forum posts
744 photos

.

By using such a sleeve you will lose an awful lot of available height. .......... 'Daylight' as Master Stevenson terms it.

Nick

John Reese01/04/2016 16:18:53
782 forum posts

Cutting down the taper might be feasible id the lathe is rigid enough. Ideally the taper would be finish ground. Depending in the existing draw bar thread size, it could be a challenge getting in new draw bar threads compatible with the 3MT. An extension adapter that jumped from MT3 to MT4 would not be feasible for at least two reasons: that type of extension holder has no provision to pass a draw bar through it; he length of that extension, in addition to using up spindle to table clearance, would result in a too stickout (from the spindle face) that would severely limit the ability to take a cut.

In short, using an extension adapter is not going to work due to problems retaining the tool and the lack of rigidity would render the arrangement nearly useless.

Go ahead with your plans to turn down the shank of your holder. If your lathe is not up to the task, find someone with a larger lathe to help out. If possible find someone with an OD grinder or toolpost grinder to finish the taper. You can figure out some way to adapt the drawbar threads.

MW01/04/2016 16:42:48
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2050 forum posts
51 photos

As people say, it's possible to buy a ready made. Or failing that, i think you could machine an arbor if you're good with your external taper machining (my humble farming hands are not), for the internal MT4 you can drill, bore and ream with a Morse taper reamer. Bore the internal angle and leave it a bit short of full size and finish with the reamer.

Michael W

 

Edited By Michael Walters on 01/04/2016 16:54:13

Sam Longley 101/04/2016 17:12:52
721 forum posts
26 photos

It is possible that you can turn down the taper. Some years ago I had a load of 22 mm drills & a reamer from a skip , all with tapered shanks. I turned half a dozen down to half inch parallel to use in a jacobs chuck. Still have one .

Could you cut one to fit say a 5/8 collet or is that too much of a bodge for a model engineer?

MW01/04/2016 18:39:36
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2050 forum posts
51 photos
Posted by Sam Longley 1 on 01/04/2016 17:12:52:

It is possible that you can turn down the taper. Some years ago I had a load of 22 mm drills & a reamer from a skip , all with tapered shanks. I turned half a dozen down to half inch parallel to use in a jacobs chuck. Still have one .

Could you cut one to fit say a 5/8 collet or is that too much of a bodge for a model engineer?

You could certainly anneal the HSS if you've got a good torch or put it in a fire. That might get it soft enough to cut.

Michael W

duncan webster01/04/2016 18:51:08
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2226 forum posts
32 photos

Annealing HSS is next to impossible with home shop equipment. As this taper is going up the spout of a milling machine it needs to be spot on. I'd invest in a ER32 chuck on MT3 taper and sell the MT4 one on e-bay. This despite my Yorkshire ancestry

Nigel McBurney 101/04/2016 19:43:03
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591 forum posts
3 photos

Avoid damaging the spindle taper of your milling machine, its no good trying to save a few pennies modifying spindle tooling and in the process spoiling the spindle which could cost a lots of cash even if a replacement spindle is available. Jump up morse taper adapters are available to suit milling and drilling machines I have a 3mt to 4mt (a naughty tool) they are not suitable for milling as they are rather long ,and milling cutter holders must be secured with a drawbar,one type is usually used for drilling when it is necessary to use a 4 mt drill bit on a 3mt machine and then only use it on very easily machined material i.e. aluminium or plastic. other types of holders for 4 mt generally have a inter 40 at the other end and again only for holding drills.

MW02/04/2016 00:57:15
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2050 forum posts
51 photos
Posted by duncan webster on 01/04/2016 18:51:08:

Annealing HSS is next to impossible with home shop equipment. As this taper is going up the spout of a milling machine it needs to be spot on. I'd invest in a ER32 chuck on MT3 taper and sell the MT4 one on e-bay. This despite my Yorkshire ancestry

Well, i dunno, i've managed to screw cut HSS endmills to fit an auto-lock chuck in the past and i heated them up and let them settle. I've got no idea what sort of nightmare you'd be in for if you tried to mill it. I've also cut HSS things to size using this method too. You're probably right though, if it means large chunks of it.

I'd agree this probably ain't worth the fuss of making this socket unless you're a die hard home maker. Whatever floats your boat i guess.

Peter Love 102/04/2016 07:44:10
12 forum posts
2 photos

Thank you all for the replies, a lot of interesting info' and advise, I have a box with about fifty various 1" threaded end mills and slots and a Clarkson Autolock type 'S' MT4 holder I can't use, my mill is an old Alpine MT3, I am in the process of making the second of my Harold Hall Myford super seven carriage stops, using a length of 20 mm steel that I have available, it would have been quicker with a larger cutter, no worries nearly there now I can then get back to the real job in hand of building the Malcom Stride Bobcat engine.


Peter Love

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