ER32 Extension

Anyone know where you might be able to get one of these?
Eccentric Engineering are out of stock.

I'm afraid not; but if I needed another one I would make one (buying in the tricky nut).

Hi Vic, I have one by HBM form RDG some years ago, it is very accurate -- maybe I was just lucky because i think this direct fitting type is problematic regarding accuracy. About 18 moths back I purchased another from RC -Machines in Europe and there were several problems, sort of resolved, accuracy acceptable but not as good as the HBM.

I like this design of chuck but the best way is to make your own, commercial one suffer from too wide a tolerance particularly on the spindle register -- they are made to P fit !!!! I also discovered the RC one had a 60* thread form not 55* Whitworth ! To produce these commercially to the accuracy required would make them far too expensive for many hobby users.

Just my two pennyworth of thoughts.

John

JohnF:

Did you mean to suggest that the thread should be Whitworth form? My understanding is that they are metric (and made a slightly loose fit so that the tapers can work as intended).

PS I couldn't see EE's chuck on their website but I'm sure Gary would answer an email query as to accuracy, availability, etc.

Edited By ega on 09/06/2021 10:38:47

A slightly sideways thought Vic - I have an ER16 extension chuck (on a 20mm straight shaft) that I can hold in my E32 fitted tools to help with access/reach problems. It is obviously limited to 10mm diameter stock/tooling but it is very useful for that odd job where you can't quite reach the work for any reason.

I imagine it might be useable in place of the 'extended' ER32 chuck on your Turnado table (which is what I'm assuming you need it for). It won't hold above 10mm but it's not as expensive and also has other uses.

Regards,

IanT

Hi unless I misunderstood Vic is wanting an ER32 collet chuck to fit a Myford spindle ? - photo here**LINK** If thats what he wants then yes the spindle thread is Whitworth form, the collet nut thread is of course metric.

John

Thanks for clarifying - very surprising to me that anyone would offer a spindle fitting with the wrong thread form even though one wonders how much difference this would actually make.

No, I don’t want an ER chuck for a Myford lathe, I want an ER32 extension as stated in the thread title! It’s for my existing (flange type) ER chuck. Eccentric Engineering list them on their website but as I said they’re showing as out of stock.

If that is what you want, why are you confusing us all by posting a picture of one that is clearly spindle-mounted?

It takes seconds to post a link to the correct item:

https://eccentricengineering.com.au/shop/ER32-Collet-Chuck-M40x1-5mm-Extender-p178489274

For those who have never seen one before, this _replaces_ the closing nut on an ER32 chuck and uses a female M40 x 1.5mm thread.

As this is not an item that is used commercially, or in any other application than the Turnado system, there is a worldwide monopoly supplier of this, Eccentric Engineering. So if it is out of stock, you have to make your own or wait.

DC31k:

Thanks for clearing up the confusion. I must admit that from looking at the EE site I had thought that the "extension" was just an over length ER collet chuck and the same sort of thing that I had made myself - over long to take account of the Myford gap bed.

I suppose that Turnado does not normally require great precision and that the two-part extender approach is defensible; all the same, it seems a shame to risk losing the accuracy of the normal one-piece article.

The link above by DC31k goes to an ER32 Collet chuck extender which screws straight onto a backing plate type ER32 Collet Chuck to extend the length from the lathe head to the work piece.

EE also have one that screws directly onto the spindle shaft of a Southbend 9 lathe (similar to the photo originally posted by Vic)

Both are listed for use with the Turnado freehand turning system so not for precision work. Both are out of stock.

An alternative is to hold an ER collet chuck extension (ER collet holder with a parrallel shank) in the collet chuck which is on the lathe. Lots for sale on ebay. 

(Possibly just an ER collet holder with a morse taper shank as they extends further from the mill head and more compact than a collet chuck mounted directly to the spindle)

Paul

Edited By Paul Lousick on 10/06/2021 11:43:59

Because that’s the only picture I could find. But really, the clue is in The Thread Title ER32 Extension! Locating some bits on the Eccentric website isn’t easy.

Paul, I did think I could mount a C20 ER32 spindle in my Chuck but I lose the ability to pass stock up to 20mm through my headstock. I may buy one at some point though as they are only about £30 on the auction site.

The only option you have if Eccentric Engineering does not have any is to make your own.

I doubt if anyone elso does.

Unless you also have a 5C chuck in which case fitting a 5C/ER32 converter would give you a similar collet position that you could get the Tornado under, but then again may as well just use the 5C

I do not follow your logic. Clearly, you have been able to locate it in order to determine that it is out of stock.

I am not sure what you want it for, but Mr ega's point is worth some contemplation: a _spindle mounted_ version of the device will locate and register on, the aptly-named spindle register. This is a parallel portion of the spindle, concentric with its axis of rotation. This is how concentricity is assured in threaded items: the thread itself plays no part in locating the device.

There is no such parallel portion on an ER32 collet chuck when the nut is removed. At best, you might have a flat face that is perpendicular to the axis of rotation*. So consider how the extension you want might achieve concentricity if the only thing joining the two parts together is the M40 thread.

* Yes, HSK connections use a face contact, but also use a taper.

Maybe you should look at your own link again.

“ER32 Collet chuck extender - screws straight on to a backing plate type ER32 Collet Chuck to extend the length”

To be honest i have one. it is spectaculary made. but!!! i get 20 thou run out off mine and thats without a collet fitted..
I suspect tthat can't be due to the collet holder as it is made so well.. not sure where to look next at improving it but thought I should bring it up. I was going to make one myself but bought this instead.
Just some food for thought.

Holding an ER collet chuck, with a plain shank in another ER collet chuck, will not only have the disadvantage of not being able to pass material through into the spindle, but possibly reduce the concentricity, by virtue of the fact that the shank and the taper for the collets will have a tolerance on the concentricity between the two.

Sod's law says that the tolerances on the original collet and chuck will be increased by the eccenticities coinciding and whatever the eccentricity is between the shank and the collet taper will add to that of the original chuck!

Daft suggestion, which will still, unavoidably, introduce extra tolerances / eccentricities.

Turn up a taper to sut the collet chuck (16 degrees overall) on a hollow extension, and then use an ER nut to clamp it in place.

The outer end of the extension will need to be screw cut and internally tapered to suit the collets and the clamp nut. without disturbing the "dummy" collet and extension assembly, to maximise concentricty.

The difficulty is going to be the means of engaging the nut when the time comes to release the "dummy taper" extension from the original collet chuck.

Maybe a two piece extension, with a groove, into which the nut can be engaged, before the outer part is fitted into position.

The two parts need to be such that when assembled, there is a groove into which the clamp nut has already been engaged.

The outer taper bore and thread need to be machined after the the outer section has been fitted to the "Dummy" collet, inner part.. (Screwed / Loctited / Heat & Freeze )

Since the extension will be hollow, it will be possible to pass longer workpieces into the lathe spindle.

But repeateability will remain to be seen. It may be necessary to mark both collet chuck and extension so that they are always assembled in the same realtive position.

The other drisadvantage will be that the extension will have a smaller bore than the original collet chuck. So an ER 32 chuck may well end up with ER25 collets on the end of the extension. But 16 mm for long pieces will be better than no through capacity.

HTH

Howard

What does ‘spectacularly made’ even mean?

Tony