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Morse taper limits ?

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ronan walsh21/11/2013 00:39:04
546 forum posts
32 photos

I was looking at indexable milling/ facing tools etc today, on one of the hobby suppliers websites and on ebay. Some of the indexable tools for a no.2 morse taper shaft were 3" in diameter which struck me as very large, then i seen a set of er 40 collets and chuck for 2mt , these collets have a capacity of over 1". Is there a rule of thumb for how large a tool the various morse taper can handle ? I realize its a bit of a "how long is a piece of string" question, but there must be some guidelines.

jonathan heppel21/11/2013 09:16:13
99 forum posts

As you said, it is a string length issue, but here's a few points to ponder.

I don't think that Clarkson's choice of 16mm/ 5/8" for its small chucks was entirely arbitrary, since they were designed when MT2 was common on quite big machines such as Bridgeports. Even then, some such chucks had stiffening rings that gave extra support. There's a law of diminishing returns dependent on variables such as workpiece material, depth of cut, feed rate, length of overhang from spindle, general machine rigidity and condition, and cutter material and type.

I believe that the maximum recommended end mill diameter for the fairly solid VMC/626 is 20mm, which is not that different from Clarkson's 16mm

Integral shank end mills, which are the stiffest of all, are seldom more than 25mm.

Face mills and fly cutters have much less overhang, so less leverage and as a result can be bigger without causing problems, but I feel that 40-50mm in steel is a practical maximum.

The huge cutters you mention IMO exist largely because there is a market for them, and not for their actual utility. As for collets, I can imagine someone having a chuck to fit a set that they already had, and only using the smaller sizes,

I expect there will be many who disagree, but this is my take on it.

Ps. I' m talking about my experience on a very solid Hayes. Modern mini-miils etc have nothing like the same capability, so sizes will need to match accordingly.


Edited By jonathan heppel on 21/11/2013 09:53:56

Pete21/11/2013 09:22:03
78 forum posts

I can assure you that your thoughts are correct. 1" diameter tool shanks are beyond the capabilitys of a R-8 taper mill if your wanting to push things to the cutting tools limits. Yes with light cuts and slow feeds you could probably buy and use the tooling. But the higher costs don't match up with the capabilitys. For a MT 2 taper mill? I'd suggest maybe 1/2" shanked tooling might be a little more logical, cost effective, and useable. With your MT 2, you won't have anywhere close to enough HP to drive a 3" diameter face mill. That's even pushing things according to Bridgeport, they mention 2"-2 1/2" diameter facemills as right around the maximum limits.Just because they build it, doesn't make some of this tooling a great idea to buy and use.

However.................... if you were to treat it like a multi tooth flycutter (and that's what it is) you could with a quality set of HSS or carbide inserts use it as a light finishing tool. You'll just never be able to hogg material off with it.


Baldric21/11/2013 09:39:04
180 forum posts
30 photos

The ER40 collets on MT2 may be more useful to hold material in the lathe rather than a tool holder in the mill.


Pete21/11/2013 09:58:40
78 forum posts

Yes and no Baldric, useing a MT 2 collet chuck removes the ability to use a lathes spindle through hole for longer shafting. And with a bit of thought, you can build a spindle mount set tru type of ER collet chuck, and using some thought that will give you the ability to get to Zero, or as close as you, your machnes bearings, and your measureing equipment will allow.A good 3 jaw should be capable of .001"-.003" runout, To make it worthwhile, a good collet chuck should be better than .001" in my opinion.


Bazyle21/11/2013 10:15:29
6386 forum posts
222 photos

Also applies to boring heads, though they are single point so less stress. For example the UPA4 comes as MT4 (not MT5) or ISO40, (but not ISO30). I rather assume the MT4 is for use in a lathe where the swing would limit the setting used and the ISO30 was not considered firm enough for the possible max swing on a mill. Not that it couldn't do it gently but some dumbo will push the limit and then whinge that the finish is poor damaging their reputation.

KWIL21/11/2013 10:34:34
3563 forum posts
70 photos

I use a 63mm insert face mill on a Bridgeport R8. As has been said it does work OK and on CI you can make it work hard, I would not however use it on steel with anywhere like the cut. Machine tool rigidity and power are in the end the real limitations.

Baldric21/11/2013 12:26:54
180 forum posts
30 photos
Posted by Pete on 21/11/2013 09:58:40:

Yes and no Baldric, useing a MT 2 collet chuck removes the ability to use a lathes spindle through hole for longer shafting. And with a bit of thought, you can build a spindle mount set tru type of ER collet chuck, and using some thought that will give you the ability to get to Zero, or as close as you, your machnes bearings, and your measureing equipment will allow.A good 3 jaw should be capable of .001"-.003" runout, To make it worthwhile, a good collet chuck should be better than .001" in my opinion.


While I agree with what you say I was thinking that an ER40 on MT2 was perhaps better suited to work holding than tool holding, however I personally don't do this as I do have a collet holder that fits on the nose of my Boxford providing the benefits you mentioned.


ronan walsh22/11/2013 01:02:18
546 forum posts
32 photos

Well the er40 chuck had a 2mt taper shaft on it for tool holding, not work holding, Maybe i am underestimating the capacity the morse tapers have to cope with tools, but i doubt it. Surely the way machine tool manufacturers limit the size of the tools to be used in their machines is by the taper they use in the spindle ?

Pete22/11/2013 04:16:11
78 forum posts


Yeah they do, but the tooling manufacturers will also build whatever sells. As I said, just because they make it doesn't mean it's a good idea. I've got that R-8 ER-40 Collet Chuck and Collets, and it will accept tooling that's too large for my mill even though it's got a 3 hp 3 ph motor on it.. But I knew that when I made a point of buying that size, I did want it for both tool holding in the mill, and work holding in the lathe. So it's a bit of a trade off since the ER-32 size would be better suited to my mill. It's made by Bison, a quite well respected Polish tool making company. And I'm sure they'd be honest enough to admit a ER-40 collet system is too large for any mill with an R-8 spindle taper even though they make the tooling to do it.

On my much smaller Emco Compact 5 lathe that does have a MT 2 spindle taper, I bought Emco's collet chuck and collets for it. There listed as a ESX-25 system. About the same as, and I think I recall reading that ER-25 collets will fit. But you also have to consider the extended length the larger collet chucks have, that moves the cutting tool much farther away from the machines spindle bearings, so the lateral forces on any cutting tool with a mill have a greater effect. It's exactly what you don't want. And usually the smaller MT-2 mills are limited enough for any extra Z axis height between the spindle nose and the mills table anyway. I personaly don't think what your loseing in Z height and tool rigidity is worth the few percieved gains your getting with the increased size capabilitys. And that larger tooling starts getting very expensive, very fast as you move up to those larger sizes that you can efficiently use anyway.


ronan walsh23/11/2013 01:51:39
546 forum posts
32 photos

I just wanted a reasonably large, say 1 1/2" or 2" diameter indexable milling cutter to use squaring up or facing stock. The work i do is a bit larger than model making usually, motorcycle parts etc.

Pete23/11/2013 02:49:39
78 forum posts

Then if it were me? I'd have a check around your general area for any suppliers that carry something in the size range your looking for. It took me a very long time to figure out, but a lot of the cheaper offshore built cutting tools come with just about worthless carbide tips. And again if it were me, I'd make a point of buying any facemill that takes the same HSS indexable tips that Warner in the U.S. makes, and the same for the well known brand name European, Japanese, or North American carbide manufacturers make. They ARE worth the extra they cost.


jonathan heppel23/11/2013 09:34:10
99 forum posts

I agree. TPXX insert cutters do work, but more by beating the workpiece into submission than cutting it. They are quite hard on the machine, and are better suited to larger mills. There are cheap APMT positive cutters around, but I've no idea how good they are. You didn't say what your machine is, but even on a solid one I'd use max 40mm on steel and 50mm on Al with MT2

Mike Poole23/11/2013 12:00:02
3383 forum posts
77 photos

Twist drills change from MT2 to MT3 at around 22mm. I imagine the torque to be transmitted is one of the reasons for the change. Large face cutters need lots of torque to drive them at capacity but a light cut should be fine and gives a nice clean finish rather than stepping over a small cutter and leaving tram lines on the job. We happily tackle jobs in the lathe that are really too big for the machine, with care it works maybe not at industrial material removal rates but it does the job. As long as you are cutting metal I think most people can judge when a machine is not happy with what we are asking of it.


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