# Why not make collet blocks for 3MT collets?



## AmericanMachinist (Sep 5, 2020)

I did some searching but didn't see much, which leaves me wondering what I'm missing..   I have a set of 3MT collets for the min-mill.   I'd like to have collet blocks.   While I'd be limited to holding round stock of roughly fractional sizes, and limited in length I can insert into the collet, what's the downside of using 3MT threaded collets with a drawbar on the back? 

When I have a project that warrants it, I'll look at picking up the appropriate Hardinge 5C or EC style collet blocks and collets.  For now I have some projects in mind for fun and learning that aren't all that critical.


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## Superburban (Sep 6, 2020)

I would say the biggest downfall is the throat of the 3MT, what maybe 1" or 1&1/4"? While the 5C, is open, so you can put any length sticking out the back.

I considered making a 3MT block, just like you, Never got around to it, besides cutting and squaring the block of steel. Then I picked up a 16" Southbend lathe, with a fairly complete set of 5C collets (including some squares). So buying the block set became a got to have.


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## rjs44032 (Sep 6, 2020)

Morse taper is a cinching or locking taper. That means that mating holder and tool will lock together without any other mechanism. This is similar to Jacobs, Brown & Sharpe, and other locking tapers.

Non-locking tapers: 3C, 5C, R8, ER, and others require a drawing nut or mechanism to lock the mating tool in place. They are easily released as well. I think this makes them more suitable for use in collet blocks.

Best Regards,
Bob


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## AGCB97 (Sep 6, 2020)

Since you already have the collets, seams like a neat project!

Aaron


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## Technical Ted (Sep 6, 2020)

I made a square and hex block for my 4C collets. I didn't make a draw bar. I made the blocks short enough so I could just use a nut similar to the commercial 5C collet blocks.

Ted


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## Janderso (Sep 6, 2020)

While we are on the subject, is MS3 the same as MT3?
I got this tooling from the Doc when he gave me an Industrolite milling machine.
I am also picturing the MT3 face mill. I measured the tapers between the two. At a quick glance they are similar


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## rjs44032 (Sep 6, 2020)

Jeff,

On cursory search I found anecdotal evidence that MS is a Chinese naming convention for Morse taper. So these are most likely Morse taper manufactured in China. Sorry I could not find a more authoritative reference.

Best Regards,
Bob


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## Janderso (Sep 6, 2020)

rjs44032 said:


> Jeff,
> 
> On cursory search I found anecdotal evidence that MS is a Chinese naming convention for Morse taper. So these are most likely Morse taper manufactured in China. Sorry I could not find a more authoritative reference.
> 
> ...


Thanks Bob.
Good to know


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## Toolmaker51 (Jan 13, 2021)

In my book dang near anything China IS anecdotal.
Rest of the whole damn planet knows MT means something, universally, just like 5C, R8, CAT, BT, NMTB, AXA, CA, TG......

MT blocks for a QCTP make sense for toolholding, little justification for part holding come to mind. Adding distance tool tip to hold down bolt require careful centering, more secure attachment of toolpost, and care in gib adjustment of cross slide and compound.


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## Illinoyance (Jan 13, 2021)

I like the ER32 collet blocks. A 5C or any similar shaped collet will only collapse .005" under nominal.  ER collets, except for the smallest sizes will collapse 1 mm.  A set of ER collets has a continuous range of holding diameters from 1mm under the smallest to the largest.


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## Toolmaker51 (Jan 13, 2021)

Illinoyance said:


> I like the ER32 collet blocks. A 5C or any similar shaped collet will only collapse .005" under nominal.  ER collets, except for the smallest sizes will collapse 1 mm.  A set of ER collets has a continuous range of holding diameters from 1mm under the smallest to the largest.


Exactly, plus a fairly easy female contour to make. Generally speaking, double split collets have better range and grip, compared to single split holders. It's all in the ability to collapse; doubles contract in a progressive cylindrical manner. ER's for example; adept holding work or tooling.
Singles are only truely _cylindrical at one size_. Deviating from that causes collapsed or sprung holders.


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