# Collet chuck question, MT vs spindle thread



## jskeen (Feb 19, 2009)

I've been seriously looking into this recently and have come up against a question I really hope someone can answer.  It seems to be pretty much universally agreed that a collet chuck with a full set of collets is a good thing to have.  So, given that as a starting point, I have seen very little (actually no) information on the relative value of the super expensive name brand collets vs the generic, (presumably chinese made) collets available on ebay.  There does seem to be a sharp division of opinion on collet chucks, and THAT is what I'm curious about.  

It seems to me that collet chucks in general are made and marketed to the metal turning industry, where extremely tight tolerances are the norm.  Most of the chucks that I have seen aimed at that market look to use some variety of taper and drawbar arrangement to mount the chuck, be it a cat 40, straight shank, or MT. That make sense.  Now some of us in the wood turning biz have used them to good effect with our toys.  But, there seems to be a broad consensus that the spindle thread mount used on the beale or it's PSI clone is much more accurate, IE has less runout than a MT chuck.   I am curious if that is true, if anyone has some hard numbers to back it up, and if so, is the difference really worth the significant price increase.  

You can get a MT2 ER32 chuck on ebay for $25 delivered any time you want.  The spindle mount versions start at almost $100 for the psi and twice that for the Bealle.  Now I grant that JR makes some extremely sexy hardware, and if I had the cash, I would own most of it just because I love good hardware.  BUT, for our uses, is the difference in performance really worth the cost?  Why?  Says who?  Inquiring minds need to know


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## Randy_ (Feb 19, 2009)

I can't answer your question about which type of collet chuck is inherantly more accurate. My gut feeling is that they are both about the same if you purchase chucks of comparable quality.
 
(Milling machines, CNC equiptment etc all use taper type collet chucks so they must be reasonably accurrate if of the requisite quality.)

The one major difference that may or may not be of concern to you is that MT collet chucks do not have a thru bore so you cannot set up an adjustable length mandrel situation without a little more effort and expense.


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## ldb2000 (Feb 19, 2009)

James , I think most agree that spindle mount is a little more accurate then MT but not by much . the more important thing about the spindle mount is that you can mount mandrels and blanks as deep as your spindle will allow but with the MT mount you are limited to the depth of the collet itself only a little over 1" . I have the PSI one and love it . It cost $89.00 and came with 5 collets and a case to keep it all together .


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## Art Fuldodger (Feb 19, 2009)

My suspicion is that much of the eccentricity of morse-taper lathes is due to the accuracy of the taper in the spindle of the lathe itself.  My lathe has never had a problem with any MT accessory, but one of my friends claims that he has never been able to get any MT accessory to work well for him.

Of course, there are other differences, too.  I try to keep my tapers clean (male and female), and I use a smart rap to seat the MT accessory.  My friend scoffs at me everytime I have to rap the other side of the chuck to get it out... but I just point out that I can get it to work well, and he can't.


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## Glass Scratcher (Feb 19, 2009)

The run-out on my PSI collet chuck is .003".  The run-out on my spindle is .004"  My total run-out is, obviously, .007".  I need to cut or get a plastic bushing to seat between the chuck and the spindle, and see if I can change the orientation and reduce the overall run-out.

I also have a MT2 collet chuck, it displays more run-out, but I am not sure it is more a problem with the taper bore than the taper on the chuck.


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## marcruby (Feb 19, 2009)

I don't like using a the morse taper any more than I have to.  It's too easy to throw off the tape with a bit of dirt.  If you can lock the taper with a both this is less of a problem, but I think using the spindle thread is inherently more accurate.

Marc


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## holmqer (Feb 19, 2009)

I checked the runout on my DVR XP.

The taper was 0.0014"
The index in back of the threads was 0.0001"

So in my case the threads are MUCH more accurate than the taper. But from a practical perspective, is 0.0014" which is around 1/700" really all that bad? Do I really need 1/10000" accuracy with wood? I suspect that 1/10000 is larger then a wood cell.


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## Randy_ (Feb 19, 2009)

holmqer said:


> I checked the runout on my DVR XP.
> 
> The taper was 0.0014"
> The index in back of the threads was 0.0001"
> ...


 
I don't think you are comparing apples and apples when you compare those two surfaces.
 
You did not measure the runout of the threads, you measured the runout of the spindle before the threads were cut.  If the threads were not well cut, they might not be any more accurate than the MT is.  Think about it.


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## Randy_ (Feb 19, 2009)

marcruby said:


> I don't like using a the morse taper any more than I have to. It's too easy to throw off the tape with a bit of dirt. If you can lock the taper with a both this is less of a problem, but I think using the spindle thread is inherently more accurate.
> 
> Marc


 
Threads can get dirty, too.


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## Randy_ (Feb 19, 2009)

Glass Scratcher said:


> The run-out on my PSI collet chuck is .003". The run-out on my spindle is .004" My total run-out is, obviously, .007". I need to cut or get a plastic bushing to seat between the chuck and the spindle, and see if I can change the orientation and reduce the overall run-out......


 
Sorry, but it is not obvious to me??  The wording of your comment is not quite clear. 
 
When you measured the runout of the chuck on the spindle, did you get 0.007" or 0.003"


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## Randy_ (Feb 19, 2009)

holmqer said:


> I checked the runout on my DVR XP.
> 
> The taper was 0.0014"
> *The index in back of the threads was 0.0001"  *


 
Not quite sure what you mean by the above??  Are you talking about measuring the runout on the unthreaded section of the spindle where the threads stop i.e., on the circumference of the spindle or are you talking about measuring the runout of the face of the shoulder that stops the chuck from screwing onto the thread any further??


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## Glass Scratcher (Feb 20, 2009)

When I had measured the run-out on the spindle it was .004".  However as you pointed out earlier, I didn't check the runout on the threads, just the shoulder above the threads, so all I can absolutley claim is with the collet chuck in place the measurement is .007".



Randy_ said:


> Sorry, but it is not obvious to me??  The wording of your comment is not quite clear.
> 
> When you measured the runout of the chuck on the spindle, did you get 0.007" or 0.003"


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## BigShed (Feb 20, 2009)

ldb2000 said:


> ......... . the more important thing about the spindle mount is that you can mount mandrels and blanks as deep as your spindle will allow but with the MT mount you are limited to the depth of the collet itself only a little over 1" .



My MT2 collet chuck (ex Ebay allows the A mandrel (1/4") to pass though but not the B mandrel (5/16").

As I don't use a drawbar with it, as it is supported by the tailstock anyway when using the mandrel, I can push the mandrel in as far as I like.


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## ldb2000 (Feb 20, 2009)

Fred , yes that is a mandrel collet chuck , we are talking about er32 collet chucks like the Beall and PSI spindle mounted collet chucks vs the MT type collet chucks . With these collet chucks there is no through hole except for the draw bar hole .


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## BigShed (Feb 20, 2009)

ldb2000 said:


> Fred , yes that is a mandrel collet chuck , we are talking about er32 collet chucks like the Beall and PSI spindle mounted collet chucks vs the MT type collet chucks . With these collet chucks there is no through hole except for the draw bar hole .



No, sorry, I am talking about an MT2 ER25 collet chuck which I use for both my A and B size mandrels. Perhaps I wasn't clear on that. Yes it has a drawbar hole right through and it will allow the A mandrel to go through that but not he B mandrel.

I have another MT3 ER25 collet chuck for my metal lathe and it will allow the B mandrel through as well.


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## holmqer (Feb 20, 2009)

Randy_ said:


> Not quite sure what you mean by the above??  Are you talking about measuring the runout on the unthreaded section of the spindle where the threads stop i.e., on the circumference of the spindle or are you talking about measuring the runout of the face of the shoulder that stops the chuck from screwing onto the thread any further??



From the face of the shoulder that stops the chuck from screwing onto the thread any further


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## holmqer (Feb 20, 2009)

Randy_ said:


> I don't think you are comparing apples and apples when you compare those two surfaces.
> 
> You did not measure the runout of the threads, you measured the runout of the spindle before the threads were cut.  If the threads were not well cut, they might not be any more accurate than the MT is.  Think about it.



You make a good point about comparing different things. 

When I measured the TIR on the taper, I in effect measured the concentricity near the exit of the taper, but did not measure deep inside the taper to ensure that the taper runs true. I should see how deep I can get the tip of my dial test indicator into the taper.

When I measure the TIR on the face that the chuck registers against I am in effect measuring the angle of deflection, but get no measure of concentricity.


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## randyrls (Feb 20, 2009)

To join the thread;  

Only the inner taper of the spindle nose, and the registration ring at the back of the spindle threads should be used to measure runout.

I have an MT3 collet set because my mill is also MT3 and the parts can be used on either machine.

Metal lathes come with an inspection record where the tolerances of the various parts are specified and the actual values listed for each lathe.

Closer tolerances and mass are what you pay for in a metal lathe.


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## randyrls (Feb 20, 2009)

holmqer said:


> I checked the runout on my DVR XP.
> 
> The taper was 0.0014"
> The index in back of the threads was 0.0001"
> ...




Eric;  I've drooled over the DVR for some time.  I almost bought one when Woodcraft was having their sale last year.


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