# Er-40 Collet Chuck For Southbend 9" Lathe



## HMF

*Reprinted with permission from Neil Butterfield
Original at http://www.nbutterfield.com/Pages/ER40ColletChuck.aspx
See Neil's store at http://www.neilsniche.com/Pages/default.aspx



ER40 Collet Chuck*

*When I first saw this construction article in the February/March 2015 issue of Machinist's Workshop magazine I knew I had to make one. I had heard about ER collets but I did not know of the most significant advantage, there are no gaps in the range of material sizes that they can hold. ER40 collets are made in 1 mm steps from 3 mm to 30 mm and each spans 1 mm.  In contrast, a 5C collet has a limited holding range of less than +.010" to -.010". With the set of 23 ER40 collets I purchased I cover 1/8" to 1" with no gaps. The collets are marked in imperial dimensions (inches) not metric.
Years ago I had made a spindle mounted 5C collet holder for my 9" South Bend lathe but I was never that happy with it. I didn't do  a very good job making it. Primarily the problem was in the fit of the collet holder counter bore and the lathe spindle shoulder. I also did not like the fact that I had to use a draw bar along with a collet internal threaded plug to clamp the 5C collet which prevented extending a long work piece through the small 3/4" spindle bore.

ER (extended range) collets were originally designed by a Swiss company and were used principally for tool holding. Lathe work holding seems a better use to me with the no gap feature. I never liked collets for holding end mills. My mentor, an old time tool and die maker, always said "why do you think the manufacturers put a flat on those end mills"? Hence the very common end mill holders. I have no milled grooves in my milling machine table. I'm told that even expensive CNC collets will let slip an end mill on occasion.   

The ER collet chuck only requires two parts, the chuck body which I made and the clamping ring or nut, which I purchased. The chuck body has a 1-1/2"- 8 threaded mount and a M50 x 1.5 metric thread for the metric collet nut. The collet nut is readily available from the collet manufacturers and much less expensive to purchase than to single point turn the metric thread on the collet chuck body. I have the capability to cut metric threads on my South Bend lathe but if one does not have the necessary gears, the Machinist's Workshop article tells how to cut a 99.8% accurate metric thread with readily available inexpensive standard lathe gears. This chuck could easily be made to fit lathes other than the 1-1/2" spindle lathe described in the Machinist's Workshop article discussed here. *

*To machine the 8° collet seat I set the angle of my compound using a sine bar resulting in a very accurate machined seat. No taper attachment required. I have a compound setting block I made some time ago which makes it very quick and easy to machine very accurate tapers. I've never used or needed a taper attachment and never understood why anyone would want such a complex piece of lathe equipment. 

I learned that very accurate ER collets can be very expensive, up to $800 for a set to be used on an expensive multi-axis CNC machine. I opted for a new imported set on eBay. I paid $132 for my 23 piece 1/8" to 1" set, less than $6 each. Included with the collets was a collet nut spanner wrench for $18 and a MT 3 arbor collet chuck with the collet nut for $46. I purchased the MT 3 collet chuck mainly for the collet nut but it was nice to have to check my metric thread. With the MT 3 arbor I can also use my milling machine or it will even fit my South Bend spindle.
I've always wondered, and never found an answer, why the ER40 collet set is sold with only 23 collets and not the 29 that are necessary for a complete set in 32nds. which would be 29 collets. When I buy a set I want the complete set so since purchasing the 23 pc. set I found a source and purchased the missing 6 collets. Purchased from www.boltontools.com for $6.95 each. they have other size ER's also. I'll probably never use them but now I have a complete set. I've changed my collet drawer to accommodate the extra 6 collets. *

*
Upon completion of this collet chuck I was pleasantly surprised. The accuracy (work piece run out) on a number of test pieces was from zero to .0015" with .0005" to .001"the norm. Hefty tightening of the collet nut and very clean collet slots is important. I know that I will be using it often and frequently using instead of my trusty 5" well worn and not very accurate, 3-jaw chuck.

Also, with this Collet Chuck I can use long material pieces up to 3/4" diameter through the spindle very accurately and shorter material up to 1' diameter very accurately.

For small work, under 1/2" I still have my very accurate 3C collets available with through the spindle capability of 1/2". But the 3C collets like the 5C, have gaps between the standard fractional sizes. Fortunately I have some 3C hex collets which I use often and they are not available in the ER system. Probably because of the 16 slots.  

For those of you not familiar with the ER collet system the collet nut, or clamping ring, has a 30° conical feature to engage the collet along with a cam feature to extract the collet. The selected collet is inserted in the collet nut first in a tillting fashion to engage the collet groove and then when the collet nut is removed from the chuck the collet is retained with the nut, preventing dropping the collet. Very nice for we clumsy old farts.
*






*Below is the Collet Chuck with the Nut installed along with
the two spanner wrenches required, 4 typical collets and
the Machinist's Workshop feature issue*




*Mounted on my 9" South Bend lathe holding a piece of brass round* 












*Spanner wrench to install the chuck on lathe 1-1/2-8 threaded spindle*




*Spanner for the Collet Chuck Nut*




*My 23 ER40 collets, 1/8" to 1"*


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## Kernbigo

I wonder if anyone makes the part you made to adapt it to a south bend lathe


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## T Bredehoft

Kernbigo said:


> I wonder if anyone makes the part you made to adapt it to a south bend lathe



I did, to fit my Clausing MK2 (1" 10 thread) lathe.  Not knowing how to thread 17 TPI, I used 16 TPI and made my own nut. 

I'm very glad Nels included the link to the source of collets, I'd purchased 3 of them and lost the connection.  I've begun again, buying just the collets I need now.


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## aametalmaster

Just make your own. I made the first ER-40 collet set up for a lathe. I have pics in my albums but its being upgraded right at this moment...Bob


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## mattthemuppet2

that's 2nd inline on my list of major projects. I think it'll be extremely useful and I'm going to use a piece of hex shaped steel so I'll be able to use it as a collet block in the mill to cut flats. Just have to get through a whole bunch of non-major projects first


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## aametalmaster




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## Holescreek

Google images of an "ER40 collet plate".  I bought one from Tools4cheap a couple years ago to use for a lathe, someday I may actually get it fitted up.


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## HMF

Holescreek said:


> Google images of an "ER40 collet plate".  I bought one from Tools4cheap a couple years ago to use for a lathe, someday I may actually get it fitted up.



Jeff Berk of Tools4cheap.net is moving and looking to get out of the machinery business. If you need something,  better get it while he's still around.


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## aametalmaster

And for little parts they can't be beat...Bob


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## dlane

Wonder if anyone makes a er 40 chuck for 10 L , 2 1/4-8 spindle . I have a set of er 40 collets but my chucks are mt 2, mt 3, r8 , be nice to use them on Heavy ten


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## aametalmaster

dlane said:


> Wonder if anyone makes a er 40 chuck for 10 L , 2 1/4-8 spindle . I have a set of er 40 collets but my chucks are mt 2, mt 3, r8 , be nice to use them on Heavy ten



Simple enough to make. Will PM you...Bob


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## aametalmaster

I always wanted to make one from brass just for looks...Bob

http://www.hobby-machinist.com/gallery/albums/er-40-collet-chuck.317/


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## martik777

I made 3 ER25 chucks, one for the 1 1/2 8 TPI spindle, one with a hex shaft, one with a straight shaft for the rotab. Best to make it right on YOUR lathe, which will provide the greatest accuracy since you will be turning the taper while it's mounted on your spindle.  If you buy the nut, you'll need to cut a 1.5mm thread. I did not have metric transposing gears on my 9A , so I substituted a 26 tooth stud gear for the 20 and set the QCGB to B4 which gives 1.50091 mm. I also made my own nut, without the eccentric, not as convenient but works ok.  I chose ER25 because I had a full set from my mill and the full collet set was only $36 vs $130+ for ER40.  Good idea to cut a male 1 1/2 x 8 TPI to test fit your chuck - wood works!


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