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View Full Version : What type of metal to use for ER collet chuck?



Jon Heron
01-19-2013, 11:17 AM
Hi folks,
I am going to be making an ER-40 collet chuck to thread onto the spindle of my 10x22 lathe.
I am still very foggy on whats what and appropriate for different applications when it comes to the metal to use.
Should I use drill rod, durabar, stainless, cold rolled or what? Should it be hardened?
I am dying of the flue here and have been doing a bunch of reading during my down time, it seems there are many different choices, just wondering what may be the best option?
I haven't been able to realy find any type of "best practice" when it comes to tool steels....
Thanks for any insight or advice!
Cheers,
Jon

Mcgyver
01-19-2013, 11:30 AM
I would want a collet chuck hardened. Unless you have the resources to grind Id and OD afterward, you probably don't want to make it from something you need to harden. Which leaves the obvious choice, a pre hardened chrome moly, say preharded 4140 which is not too difficult to find locally. Its a little tougher to machine than regular mild steel but you want the chuck to be durable.

Not sure if chrome moly prehard is hard enough for the ideal collet chuck...its choice is on the assumption you don't have cylindrical grinding equipment. If you do, tool steel hardened, tempered and ground would give a more durable surface to where the collets mount.

You wouldn't considering buying a chuck and adapting it to the lathe?

Jon Heron
01-19-2013, 11:44 AM
Thanks Mcgyver.
So I guess that means that tolerances change on tool steel when you harden it? That makes sense.
I dont have any grinding equipment either, just the lathe, bench grinder and a drill press.
I have looked at a few of the collet chucks on ebay, I found they either are attached to a MT4 taper which eliminates passing the stock through the head, or chucks on back plates which would take away some of the accuracy compared to machining my own chuck in place on the spindle. Does that sound reasonable?
I am just getting into this as a hobby and I dont anticipate doing any heavy duty work with this thing anyways, not that my crappy lathe could do heavy duty work if I wanted it to. ;)
I will call the metal supplier this week and see if they have any 4140 round stock. Can I machine that with HSS?
I already bought some 2" aluminum round stock to make a copy of my spindle register, thread and a plug gauge and I am looking forward to building my own!
Cheers,
Jon

Boucher
01-19-2013, 11:54 AM
Jeff @ Tools4cheap sells these : http://www.tools4cheap.net/proddetail.php?prod=er40plate Here is a picture of a ER 32 on my lathe. I did a shrink fit installation to the backplate machined on my lathe.
The smaller chuck was the only ground surface available to check the run out. It was less than 0.001
http://i109.photobucket.com/albums/n50/boucherbyron/ER-32Collet.jpg

It is easy and accurate to fit one of these to a chuck back plate on your lathe.
If I were going to make on My choice for material would be 1144 Stressproof.

Boucher
01-19-2013, 12:09 PM
Jon, If you are stuck at home and want to do some reading, take a look at this thread over on PM site
http://www.practicalmachinist.com/vb/gunsmithing/er40-collet-chuck-fixtures-249118/

Down about post #20 he describes the shrink fit technique.

RussZHC
01-19-2013, 01:55 PM
Hey, info you want, info you get.
The link Boucher posted is quite good, lots of info and explanations as to "why fors"
Also:

http://bbs.homeshopmachinist.net/threads/42521-Making-a-ER-32-Collet-Chuck

and

http://www.homemodelenginemachinist.com/f13/building-er-collet-chuck-scratch-myford-ml7-5179/

and

http://www.practicalmachinist.com/vb/members/aametalmaster/albums/er40-collet-chuck/46359-collets-box/ really good photos, never did find the text to accompany if there was

If you need good dimensions (there are a few other ER threads asking about that) go to rego-fix.com (Swiss) and in their technical information they have dimensions for both internal and external nut versions of the ER system.

I am looking at similar projects once it warm up...that Swiss link was helpful in that you can not quite pass 1" stock through the largest common ER 32 (23.5mm is "it") so I need to go to ER 40 etc. [common because in some sizes there are "specials", though not sure what the details are that make them so other than they go fractionally larger than "common"]

PM me if you want more links, ones above were sort of culled/useful in my eyes

Mcgyver
01-19-2013, 02:04 PM
I will call the metal supplier this week and see if they have any 4140 round stock. Can I machine that with HSS?



yup, if you're buying, you want the prehardened not the annealed (else you have to heat treat it). When heat treating, the metal can move or warp slightly and you can't depend on the geometry being the same....but once its hardned you can't turn or mill it. This is why things you get that are hardened are ground.

Jaakko Fagerlund
01-19-2013, 02:20 PM
Other option is to use basic steel and caseharden it. Can be turned in the lathe after hardening, just needs a ceramic insert. But I would prefer ground, especially if ground while mounted to its final destination.

Toolguy
01-19-2013, 03:40 PM
Sometimes pre-hardened 4140 is known as 4142.

JCHannum
01-19-2013, 05:27 PM
Maybe Jan from Tall Grass Tools will chime in. He sells an ER32 collet chuck for 1-1/2-8 spindle noses and has made other sizes as well.

While hardened steel might be nice, I wonder if it is requisite for the occasional use a HSM would expose it to. The 5 C collet adaptor for my lathe is not hardened and the spindle of my Rockwell mill does not appear to be hardened via file test. With an ER collet, the slots in the collet will position randomly, and I doubt they would set up a wear pattern.

I would think the problem would be less with the seat and more with wear or deformation of the threads. This could be possibly overcome by using a larger or different thread design than the standard. If used for work holding, a larger capnut could be used without interfering with the function of the chuck.

Jon Heron
01-19-2013, 06:21 PM
This place is the best!
Lots of good stuff for me to research...
So does tempering 4140 also possibly cause things to go out of spec?
Thanks all for your input!
Cheers,
Jon

ammcoman2
01-19-2013, 06:45 PM
I made one for ER25. Used 1144 and am pleased with the results. Didn't bother with heat treating as I am not in production. After about 2 years of occasional use there is no discernable runout.

I gather that 1144, when heated to red and then dunked in oil, gives good results (about Rc 45). Apparently with neglible distortion but I haven't tried it.

Geoff

Boucher
01-19-2013, 07:44 PM
17-4 PH Stainless is stable enough for most post machine heat treat. I have been told that it is readily available but have never ordered any.

TGTool
01-19-2013, 11:35 PM
Actually my customers might be the best ones to ask. I've got the first one I made of 1018 that I've used for about 10 years of occasional use with no signs of wear. Projecting the current trend it will last my lifetime in home shop use. If I were a production shop using it all day every day it might be different.

The only other piece of data that I can contribute is from a customer who has one or more NC wood routers using an ER-25 collet on the spindle. He approached me because his spindle threads were wearing out and replacement spindles were maybe $3000. I've made several extended nuts for him to take advantage of unused threads on the spindles of the machines. It gives him a second chance at least before the really big overhaul.

So on the question of "will unhardened collet adapters wear out?" I haven't seen or heard of it yet. And remember since it's unhardened, you have the opportunity to skim cut and restore it.


Maybe Jan from Tall Grass Tools will chime in. He sells an ER32 collet chuck for 1-1/2-8 spindle noses and has made other sizes as well.

While hardened steel might be nice, I wonder if it is requisite for the occasional use a HSM would expose it to. The 5 C collet adaptor for my lathe is not hardened and the spindle of my Rockwell mill does not appear to be hardened via file test. With an ER collet, the slots in the collet will position randomly, and I doubt they would set up a wear pattern.

I would think the problem would be less with the seat and more with wear or deformation of the threads. This could be possibly overcome by using a larger or different thread design than the standard. If used for work holding, a larger capnut could be used without interfering with the function of the chuck.

Jaakko Fagerlund
01-20-2013, 04:01 AM
This place is the best!
Lots of good stuff for me to research...
So does tempering 4140 also possibly cause things to go out of spec?
Thanks all for your input!
Cheers,
Jon
I would say that any heat treatment on any metal workpiece will distort it somehow, especially if hardening. All the internal stresses and the direction in which the part is quenched all contribute to getting a banana or propellor out of the oven. Some steels will shrink a little, some steels will grow remarkably in size etc. And the shape of the workpiece also influences how it behaves when heat treated.

So to recap: Always finish machine the workpiece after heat treatment.

JohnAlex141r
01-20-2013, 09:45 AM
Jon;

FYI - the Emco collet chucks I have are not hardened. I don't think the Schaublin (sp?) ER25-MT2 is either.

Ok - for my ER16 for my CNC mill, I just made it out of an MT2 arbour from a local store.

The ER-40, the L00 backplate came from Jeff @tools4cheap.net (shipping via USPS/ Canada Post no problem for him) The metal for the ER-40 chuck came from an old hydraulic piston; did not the mirror finish I wanted on it, but for home use, it's more accurate than I can generally measure, so it's fine for me.

BTW, setting the compound slide to the 8degree angle was actually easy, accurate machined surface in lathe, dial indicator in toolpost, a bit of calculations before hand, and over a compound movement of (say) 25mm, being within 0.02 or 0.01mm is not too bad.

Another JohnS

Jaakko Fagerlund
01-20-2013, 01:58 PM
Another option is to find a used CAT/BT 40-50 collet chuck off ebay, cut off the back end of the taper and machine it to fit your spindle. Some abrasive wheels and small grinding stones will get through the case hardening, where you can then proceed with normal machining techniques.
Don't need grinders to get through the skin on case hardened part, a regular carbide insert works just as good, just needs a push to get through. Sure it wrecks that insert, but it is a lot nicer (especially in the long run) than using angle grinders etc.