ER20 Collet Chuck Modification?

[RJWParticipant @rjw]

I would be interested in opinions and suggestions to help solve a bit of a conundrum I find myself in!

I have a Unimat SL lathe/mill, which has a 12mm x 1mm spindle nose, it also appears to have an MT1 taper, but with no access for a drawbar, there's no joy down that route unless I can bore out the spindle!

I have a virtually unused ER20 collet set with chuck (2MT) which I'd like to use on it, (sans chuck as wrong MT), mainly because I can't afford to stump up for another expensive kit when I've already got something suitable for my needs,

I've searched everywhere for an ER20 flanged chuck or something with a thread size to suit the Unimat but no joy,

There seems to be plenty of ESX 16 / 32 collet sets and flanged chucks around, but ESX 20 doesn't seem to exist, which I believe (I may be wrong) is the same as the ER20!

I'm now pondering the route of buying another ER20 chuck to modify by machining and tapping the end 12mm x 1mm to suit the Unimat, which is where the plot thickens!

I know the chuck material is hardened, but would anyone know if it would be possible to soften the end enough on one to modify and tap it out without knackering the business end for the collets!!

Another slight difficulty is that my Myford will be out of commission for the forseable future, so any machining has to be done on the Unimat or an 8mm Boley!

I'm using the lathe/mill for fairly light duty clock repairs, so it won't ever be chewing off big chunks of material.

Any comments would be much appreciated, or even alternatives I've not thought of!

Many thanks in advance,

John

[RJWParticipant @rjw]

[David LittlewoodParticipant @davidlittlewood51847]

John,

Would you not be better off making the body of the chuck from scratch? You can use the same nut (which would be harder to make) and an M12 x 1.0 finishing tap would make getting a good finish on the holding thread easier. Turning the female taper for the collets need not be that tricky once you get the angle set on the topslide – a test piece might be worthwhile here – and the external thread for the nut is not critical to the accuracy.

One of the main points of using a collet chuck is the guarantee of concentricity; cutting the M12 x 1.0 thread (on any lathe) and then turning the taper on your own Unimat will give you the very best chance of concentricity.

As to material, I think you would find that FCMS would give you decades of use, for anything but the heaviest user.

David

Edited By David Littlewood on 19/08/2012 18:32:20

[AndyfParticipant @andyf]

John,

As David says, making your own ER chuck might not be too taxing. Here's a how-to for an ER25 version to screw on a Myford nose. As you will see, it includes a false start. Obviously, you would need to adjust the dimensions to suit M12x1 and ER20. The dimensions and taper angle (16 degrees included) can be found if you go to Collets > ER Collets and Collet Chucks on Arc Euro Trade's website.

Andy

[RJWParticipant @rjw]

David and Andy, Thanks for the comments and very informative link,

The one problem I'd have making a chuck body, is that I don't have access to anything to cut the thread for the cap nut, or a suitable die which I think would cost a fortune, especially for a 'one off' job,

What I was really after initially was something along these lines to fit onto a suitable faceplate:

http://www.arceurotrade.co.uk/Catalogue/Collets/ER-Lathe-Collet-Chucks

Unfortunately ER20 doesn't exist in this type of chuck, hence my ponderings about modding an ER20 chuck with a suitable shank size, although achieving the concentricity you mentioned was something nibbling away at the back of my head!.

I'll cast around for a die anyway and take things from there,

Thanks again,

John.

[blowlampParticipant @blowlamp]

What about modifying this collet chuck?

Martin.

[speelwerkParticipant @speelwerk]

Once tried to soften a hardened 2mt centre, even after several hours of glowing

it was still too hard to be worked with normal tools.

[MICHAEL WILLIAMSParticipant @michaelwilliams41215]

Hi RJW ,

Before doing any more I suggest you have a rethink . An ER20 collet system is way too big for such a tiny lathe .

Regards ,

Michael Williams .

[blowlampParticipant @blowlamp]

In my experience, these chucks aren't usually hardened, but they are made of quite tough steel and can be worked with HSS or tipped tooling with a little care.

Martin.

[RJWParticipant @rjw]

Martin, that's pretty much what I had in mind, chop the shank off, then bore and tap the body to suit the 12mm x1mm nose, much easier said than done of course, but there's room to do it without anything fouling the collet.

Michael, in a different situation, I'd probably have bought the smaller ESX16 set with a flanged chuck and another faceplate, but as things are, I have to cut my cloth accordingly and adapt what I've got,

The lathe does swing either an 80mm faceplate or a 73mm scroll chuck, (standard Emco Unimat kit)! whereas the ER20 chuck body measures 34mm dia (nut) x 42mm long body overall, and with a collet is both significantly smaller and lighter than either the chuck or faceplate, so i'm not entirely sure why you think it's oversized for the lathe, even my 8mm Boley happily swings a 65mm scroll chuck,

As said earlier, I'm mainly doing light duty clock repair work with it, pivot and wheel repairs and polishing and the like, but I'd prefer to use collets for (small) milling cutters when I eventually use the headstock as a miller, (crossing out brass wheels etc) and it would be more cost effective to adapt the set I already have if possible.

John

[David LittlewoodParticipant @davidlittlewood51847]

John,

I shudder to think what the concentricity would be like if you did it by chopping off a morse taper shank and machining a female M12 x 1.0 on the corpse – even on a larger lathe. That would completely vitiate the advantage of using collets. At least using a backplate and flanged chuck you can turn the backplate on your lathe and have a decent chnce of getting it true.

David

[John Stevenson 1Participant @johnstevenson1]

David, true but the OP is having problems locating a flange mount ER20 collet chuck and he wants that size to suit what collets he has.

[blowlampParticipant @blowlamp]

The spindle nose looks like a similar arrangement to Myford, so getting it to run true shouldn’t be too hard to do.

Martin.

[Ady1Participant @ady1]

You would need to use a myford sized lathe for any hope of reasonable concentricity with a thread

The taper in these tabletop units is closer to MT0 than MT1, like with a Cowells lathe, but unimats are nowhere near as stiff or as well made

The faceplate system sounds like your best chance of success IMO

[Roderick JenkinsParticipant @roderickjenkins93242]

Making your own chuck is definately the way to go – David may even publish my article on making an ER25 to fit the Worden one day. Incidentally, I bought the sort off ER chuck that screws directly on to the Myford nose. The runout was un-acceptable but I was able to re-turn the taper with a nice new tipped tool – so not too hard.

Rod

Edited By Roderick Jenkins on 20/08/2012 09:36:04

[Michael Cox 1Participant @michaelcox1]

John,

Provided the purchased chuck is machinable then I do not think it is too difficult the bore and thread it concentrically. Once you cut off the Morse taper you are left with just the ER25 chuck part. Take a piece of bar in the three jaw chuck of the lathe and turn it down to the largest size that will fit into an ER25 collet. Now mount the ER25 chuck part of the on the turned down bar using a collet and cap nut. Now the chuck part should be concentric with the axis of rotation of the lathe and it can be drilled bored and threaded. I would single point thread the part rather than attempt to use a tap.

I hope this helps

Mike

[David Clark 13Participant @davidclark13]

Hi Roderick

That one does not ring a bell.

Was it by email?

Hi RJW

Why not get a cheap collet attachment to take your collets and mount it on a Unimat faceplate?

The faceplates are often available on Ebay.

A simple turning job would have it running true.

The Unimat does not have a taper, it is something like a parallel hole about 8, 9 or 10mm bore.

ES are different to ER

regards David

[RJWParticipant @rjw]

Thanks again all for the comments,

Rod, I'd be interested in seeing your article when eventually printed,

Mike, thanks for that train of thought, I was pondering how best to get concentricity, and your idea sounds like the best route If I need to go down it,

David, I've hunted all over the shop for an ER20 flange mounted collet chuck that could be mounted into a faceplate, but they don't exist, or at least I've never found one,

You're right about the spindle bore too, it is parallel, I'd never really bothered to check to be honest because the spindle is solid, so no means of getting a draw bar through to hold a chuck anyway.

I think I've found a solution though, not ideal, but as close to a flange mount I'll find, I'll will know better when it arrives, ebay item number 200807183267

I bought the ER20 chuck on eBay yesterday, which has a parallel shank, but it also has a flange which locates against a machine's spindle nose, the flange isn't big enough to drill and tap, but it will set into a faceplate which can take clamping bolts, perhaps allen cap screws, I can drill and tap true for them on my CMD10 mill (which does take the MT2 ER20 set I've got)! and I'm not likely to be chewing big chunks of metal with it, so I'm not concerned about the risk of anything ripping the chuck out of the faceplate, I don't think the Emco would have enough grunt anyway, even if I was stupid enough to try it.

Will keep you posted on progress!

John

[David LittlewoodParticipant @davidlittlewood51847]

Posted by David Clark 1 on 20/08/2012 10:05:04:

ES are different to ER

This is true, and they are not properly compatible – but I don't think anyone mentioned ES collets. John referred to ESX collets, and I believe these are compatible with ER. This page is quite helpful on the subject: **LINK**

David

[RJWParticipant @rjw]

David, many thanks for the confirmation on ER & ESX collet, and especially for the link, I'd completely forgotten about that site, and I already had it bookmarked!

The collet chuck arrived today, a superb bit of kit too!

There'll be a bit more overhang than I'd have liked, but it won't be whirling anything big around, so should be ok, all I have to do now is chop the end off and set the flange into an adaptor!

Also managed to pick up a scrap Unimat, and there's enough there to convert into a dedicated miller, which will save a lot of faffing around!

With the scarcity and price of tooling that is available to fit these things, I'm beginning to regret buying it a tad and that I'd gone for a Unimat 3 instead!

Such is life!

John

[KWILParticipant @kwil]

MSC (J&L) have backplate mounted ER collet chucks from ER16 upwards, not cheap but if need must.

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