View Full Version : ER Collet Chuck Conundrum
01-21-2011, 12:52 PM
Did I spell that right?
Anyway, I have these two Kearney Trecker 2D mills, both of which use proprietary collets that are no long manufactured. I've only got a handful of collets: 1/8, 1/4, 5/16, 3/8, 1/2, 1/2 to share between both machines!
I recently bought a set of Chineese ER32 collets and I would like to buy a 1.25" straight shank chuck and adapt it to my mills. They have a NMTB 30 taper but since the entire spindle assembly moves in a circle, they don't have a draw bar. Instead, the taper is retained by a nut and it has been modified with two flats on either side. (See picture).
The trouble is, collet chucks are supplied hardened. I've got plenty of carbide inserts and I've even got some Kyon ceramic inserts. I thought maybe I could burn up a bunch of carbide hard turning the shank, but I still need a way to produce the flats.
I suppose I could try to rig up some sort of tool post grinder and grinding jig to get the flats. The flats don't appear to be very precise. Alternatively, I could make the whole thing from scratch using some old axle shaft (4130) and then harden it, but I worry about the dimensional stability of the part through the hardening process. Maybe I should be looking for a NMTB 30 shank collet holder and just grind flats in it more or less by hand? What do you all think?
This is the factory supplied collet chuck which takes their own "Z" collets.
01-21-2011, 01:02 PM
Are you referring to one of these chucks?
I just bought one & turned down the shank plus bored out the through hole to 20mm. It's tough steel but does machine OK with the nuttin' fancy carbide I have. The drilling & boring was done with HSS tooling come to think of it cuz I don't have any big carbide drills. Had to go slow with lotsa oil.
The collets you have appear to cover all the end mill shank diameters you're likely to need; what else do you want to hold?
But "just for the heck of it" is a good enough reason too. I'd lean toward the idea of making what you need from the 4130 and using them as-is. Don't worry about hardening. As long as you're not a total ham-fist when you use them, they ought to stand up okay. If, after 20 years, they wear out, make new ones.
Or use pre-hardened 4140. It's not so hard that you can't machine it.
Here's an E32 collet chuck with NT30 shank http://www.ctctools.biz/servlet/the-60/ER32-NT30-COLLET-CHUCK/Detail
Is that the taper you're looking for?
01-21-2011, 02:09 PM
It sounds like what you have is K&T Die Mills. Those are awesome machines! They are about the next thing to CNC. I think Dickeybird found your answer. I would get one of those and a set of collets and turn down the 1-1/4 shank to fit the spindle. It will turn OK with carbide.
01-21-2011, 04:25 PM
If you need to make wrench flats, an angle grinder works wonders, Reguardless what it is.
Or any other type of abraisve grinder.
The only tricky part is getting it resonabley parallel at the size you want. but its easy enough with some pratice.
01-22-2011, 02:08 PM
If you 2D spindles have drive keys that mate with the keyways in the 30NMTB toolholder flange, you may consider adapting an Erickson 30 Quick Change locknut to your 2D spindles. Then you should be able to use most 30NMTB and any 30 Quick Change toolholders. The threads in the Erickson locknut are 2-3/8-16 pitch and, as I recall, the 2D spindle has a 2-1/4-12 pitch thread.
Kennametal sells the Erickson 30 Quick Change locknut: QC30QCLN and the spanner wrench is HSW30QC.
The NMTB shank was developed for use in the NMTB spindle which uses a draw bar to pull the shank up into the spindle. As a result, small variations in the tool holder flange thickness and the distance from the gage line of the taper to the outward face of the flange were not an issue when selecting one manufacturer of tool holder versus another.
The Erickson Tool Company developed the Erickson Quick-Change spindle to use the NMTB 30, 40, 45 and 50 tool holders already in existence. The Erickson QC system does not use a draw bar, it uses a quarter turn "locknut" to push and hold the tool holder taper up into the spindle. Two "lips" in the nut push against the outer face of the tool holder flange. The key dimension that causes some NMTB holders to not work in an Erickson Quick-Change spindle is the distance between the taper gage line and the outer face of the flange (dimension L4 + L5 in above tables). L4+L5 on some NMTB holders is too large which does not allow the "lips" in the QC nut to engage the outside face of the flange.
The other issue is that the flange diameter (D5) on some NMTB holders (mostly cheaper imports) is too large to fit in the mouth of the Erickson Quick-Change spindle.
All NMTB holders made by Erickson work fine and I've read that Collis and Valenite holders work fine (at least the ones made in the last 15 years or so). I've also heard that Kennametal NMTB 30 holders work well. The compatibility of other holders is in question. However, all is not lost, the flange face and/or flange diameter of the holders that do not fit can be turned or ground down a small amount and then they work just fine. Erickson even put out a procedure to do this very thing (does anyone have a copy of the Erickson procedure ?).
The "tail" of the NMTB shank is not required when mounting in an Erickson Quick-Change Spindle. So 30-Taper and 40-Taper tooling, without tail, work fine as long as the taper and flange dimensions are correct. DO40 and DT50 tooling can also be used in Erickson Quick-Change spindles, but you may need to cut off or grind down the ribbed tail for clearance in the QC spindle.
The "Erickson procedure" as mentioned above:
01-22-2011, 02:14 PM
I got couple ER32 1.250 straigt shank collet chuck made from 17-4PH, let me know if you interested.
01-22-2011, 06:30 PM
The ER collet chucks machine OK with HSS and pipe oil (this based on a sample of two that I've modified so far). I used slow spindle speed, 50 - 60 SFPM, higher might work too, I didn't try it.
01-22-2011, 08:00 PM
I have a different suggestion. The hard part about making ER collet chucks is making the nut. But you can buy those - pretty cheap. Turning the chuck itself is pretty easy. Once you are set up to make one, you can easily make several. You would also have to turn the taper on the rear to match your mill, but you have to do that in any case. I have a document with the drawings for ER collet chucks - I can send it tomorrow afternoon if you are interested. PM me with your email addy if so.
The collet in the holder looks like a universal engineering collet . I could be
wrong i cant see the whole collet . They can be found on e-bay quite easy.
Take a look at these the double angle collets . they come in ranges of WW. ZZ, z and as such . in all decimal sizes. .
Also a carbide end mill running slow 500 rpm are less will machine the flats you need . Cut keys in Thompson shafting all the time and mill flats on it to.
01-22-2011, 10:48 PM
Yep it's a 2D - thanks for all the suggestions, guys. I'm actually looking at a NTMB 30 shank ER32 chuck for about 30 bucks, including shipping. I may do that and see what kind of luck I have. If I can modify it to work, I think I'll make a couple of my own and just buy the nuts as suggested.
Thanks again. We'll see how it goes...