# 8520 owners: MT2 to ER25 Collet Adapter



## Splat (Jul 4, 2014)

*MT2 to ER25 Collet Adapter*

(edit) I should have posted this in the Machine accessories forum but was thinking about my Johannson B12/Clausing 8520 mill at the time since I had been searching around about it.

Anyone using an MT2 to ER25 adapter such as *this* one? I haven't had any problems with using MT2 so what's the big deal with the ER25 collets? Do they grab better than MT2 tapered collets? I can see the upside of leaving the chuck in the spindle and just changing out the ER25 collets but is that the only upside?


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## Don B (Jul 4, 2014)

*Re: MT2 to ER25 Collet Adapter*



Splat said:


> Anyone using an MT2 to ER25 adapter such as *this* one? I haven't had any problems with using MT2 so what's the big deal with the ER25 collets? Do they grab better than MT2 tapered collets? I can see the upside of leaving the chuck in the spindle and just changing out the ER25 collets but is that the only upside?



I'm not 100% sure but I think the ER25 collets can go larger in size than th MT2, I made a U2 to ER20 holder for a Single Lip Grinder I have, the U2 collets are hideously expensive and the ER collets offer a better size range than the U2, ER collets collapse at both ends as there compressed so each collet has a from/to size, I think with a MT collet you need to stay fairly close to the nominal size of the collet to obtain proper holding power.
Edit: the ER collets would be easier to change as well rather than screwing with the MT draw bar.


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## 34_40 (Jul 4, 2014)

*Re: MT2 to ER25 Collet Adapter*

I was asking myself almost the same question.  I just got a set of collets from tools4cheap for my 8520.  I see many sizes of "ER" collets but am unsure which way to go and if the advantage is enough for a hobby guy like me.?.?  One thing I know is that we would be limited in the size flycutter we can use, unless we go into the "ER series",  And I don't see any advantage / disadvantage to loosening the drawbar or the collet.  Have to turn something right?)



Splat said:


> (edit) I should have posted this in the Machine accessories forum but was thinking about my Johannson B12/Clausing 8520 mill at the time since I had been searching around about it.
> 
> Anyone using an MT2 to ER25 adapter such as *this* one? I haven't had any problems with using MT2 so what's the big deal with the ER25 collets? Do they grab better than MT2 tapered collets? I can see the upside of leaving the chuck in the spindle and just changing out the ER25 collets but is that the only upside?


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## francist (Jul 4, 2014)

I guess it might make sense if you wanted to share the same set of collets in the lathe and be able to pass through the headstock. I don't think MT allows that to happen, or does it?

-frank


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## awander (Jul 4, 2014)

francist said:


> I guess it might make sense if you wanted to share the same set of collets in the lathe and be able to pass through the headstock. I don't think MT allows that to happen, or does it?
> 
> -frank



The ER-25 collet adapter will need to use a drawbar, and so you still will not be able to pass stock through the headstock. 

You might get a bit longer piece of stock in there before it hits the drawbar, as the ER-25 adapter will be slightly longer than an MT2 collet.


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## wa5cab (Jul 5, 2014)

The advantage of the ER collet design is that both ends of the collet compresses, so they have a slightly wider effective diameter range than does an MT2 (or other MT) collet (roughly +/- .02" compared to +/- .01" for ER25 versus MT2).  If you are using an ER chuck on a spindle that permits front mounting (i.e., has a threaded nose or other mount for attaching the chuck), then you will be able to pass work through them up to the ID limit of the spindle.  However, if you use an MT to ER adapter chuck, that isn't the case.  Also, a search of one local catalog (Bass Tool) indicates that a collet chuck and full set of ER25 collets is considerably more expensive than a full set of 2MT.  However, Bass doesn't ID import versus USA, so that might be part of the difference.

ER25, which seems to be the only size anyone here ever mentions, is not the largest.  There are also ER32, ER40 and even ER50.  ER40 is roughly equivalent in size to a 5C, and most makers offer them in diameters up to 1".  However, sticker shock may be a hazard.  :thinking:  

Robert D.


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## Splat (Jul 5, 2014)

*Re: MT2 to ER25 Collet Adapter*



34_40 said:


> One thing I know is that we would be limited in the size flycutter we can use, unless we go into the "ER series",  And I don't see any advantage / disadvantage to loosening the drawbar or the collet.  Have to turn something right?)



You can get a 5/8" end mill holder with an MT2 taper. That's the biggest size end mill holder I've seen with an MT2 taper. I have a 2.5" fly cutter with an 5/8" shank. I haven't used it yet but plan to soon for a little project I have. I think with our machines 2.5" may be the biggest we could use satisfactorily. FWIW, I've opted against the ER25 adapter. I've been using the end hill holders now with seemingly better success than using collets to hold the tooling.


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## wa5cab (Jul 5, 2014)

One comment I'll add on the subject of MT milling cutter holders - for whatever reason, they seem to be more plentiful in the tang type than tapped for drawbar.  Or at least I've somehow accumulated a stack of them with tangs.  I've learned the hard way not to trust them at least in anything with a vertical spindle.  Sooner or later, one will let go and the cutter will drop onto your workpiece.  The best that you can hope for then is a ruined part.  The most dangerous tool to have that happen with would probably be a fly cutter, especially of the spindle has a tang drive slot.

Robert D.


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## Splat (Jul 5, 2014)

wa5cab said:


> One comment I'll add on the subject of MT milling cutter holders - for whatever reason, they seem to be more plentiful in the tang type than tapped for drawbar.  Or at least I've somehow accumulated a stack of them with tangs.  I've learned the hard way not to trust them at least in anything with a vertical spindle.  Sooner or later, one will let go and the cutter will drop onto your workpiece.  The best that you can hope for then is a ruined part.  The most dangerous tool to have that happen with would probably be a fly cutter, especially of the spindle has a tang drive slot.



I've seen more in the "Type B" style, which is the 3/8-16 threaded, than tanged around here. Just to clear up, are you saying you don't prefer mill holders at all or just the tanged type?


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## wa5cab (Jul 5, 2014)

Interesting.  I wish that the Type B had been more common around here.  Converting them is going to be a PITA.  

What I meant was that I don't trust the tanged type.  I have full sets of 2MT, 3MT, 3AT and 5C collets but if I had a full set of the drawbar and set screw type milling cutter holders, I would probably use them most of the time.  As I don't, I usually use the Atlas set with reducing bushings if I have the end mills with shank diameters to fit.  If I don't, I generally use the 3MT collets.  I'm talking about in the Atlas 3996, of course.  I don't have the MFA up and running yet.  But when I do, the only difference will be 2MT instead of 3MT.

Robert D.


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## Splat (Jul 6, 2014)

wa5cab said:


> Interesting.  I wish that the Type B had been more common around here.  Converting them is going to be a PITA.  What I meant was that I don't trust the tanged type.  I have full sets of 2MT, 3MT, 3AT and 5C collets but if I had a full set of the drawbar and set screw type milling cutter holders, I would probably use them most of the time.  As I don't, I usually use the Atlas set with reducing bushings if I have the end mills with shank diameters to fit.  If I don't, I generally use the 3MT collets.  I'm talking about in the Atlas 3996, of course.  I don't have the MFA up and running yet.  But when I do, the only difference will be 2MT instead of 3MT.



Gotcha. Well, Grizzly has them *here*. They're probably the same ones I have. Asian made, most likely, but they work fine for me. It's nice not having to worry about loosening collets to change end mills (same shank size, of course) and I've never had an end mill pull out like I had with a collet.


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## wa5cab (Jul 8, 2014)

It's odd that they skip 1/4", 5/16" and 7/16" which are common shank diameters for 1/32" and 1/64" increment end mills.  Guess that I'll proceed with my plan to mod the tanged ones I have.

Robert D.


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## stupoty (Jul 8, 2014)

I may have said this before but my mt3 er32 collet holder is probably the most benificial item i have purchased for speeding up mill work.

i have a round coloum mill and its very helpfull that i dont have to raise and lower the head very often when switching from mills to drills.

also i dont have to pound on the draw bar all the time to change cutters 

another benefit is the seamless holding range from 2-20mm so i can use both metric and imperial end mills no problem.

On the other subject passing stock through the collets, i unfortunetly dont have an er collet chuck but have made a hollow draw bar for my MT3 collets that i use ocasionaly on my lathe, very limited in pass through as the wall gets quite thin, i think 8mm is the max i can pass through the collet.

Stuart


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## Splat (Jul 10, 2014)

Since picking up some endmill holders (one of which is a Bison I got a deal on) I'm starting to really like them over using collets to hold endmills, fly cutters, etc..  Unless I'm mistaken I'm getting more rigidity and better cuts.


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## Metalflames (Nov 29, 2014)

I just recently purchased a MT2 to Er32 collet set for my 8520 and am very happy with the set up. ER32 will run up to a 3/4" collet which allows for some larger end mills. I have some 1 1/16" end mills with 3/4" shanks.


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## 34_40 (Nov 30, 2014)

Metalflames said:


> I just recently purchased a MT2 to Er32 collet set for my 8520 and am very happy with the set up. ER32 will run up to a 3/4" collet which allows for some larger end mills. I have some 1 1/16" end mills with 3/4" shanks.



That's great news. Thanks for the update.


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