3 Jaw self centering ER chuck

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3 Jaw self centering ER chuck

This topic has 28 replies, 14 voices, and was last updated 21 February 2019 at 06:26 by Joseph Noci 1.

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19 February 2019 at 14:59 #397011
John McNamara
Participant
@johnmcnamara74883
Hi All

I Stumbled on this web site
An Australian engineer living in Vietnam.
An unusual way of holding an ER collet.

**LINK**

Video Link
**LINK**

Regards
John

Edited By John McNamara on 19/02/2019 15:02:11
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19 February 2019 at 14:59 #19246
John McNamara
Participant
@johnmcnamara74883
An unusual tool
19 February 2019 at 19:16 #397042
Michael Gilligan
Participant
@michaelgilligan61133
Thanks for the link, John

An interesting idea !

MichaelG.
19 February 2019 at 20:58 #397065
mark costello 1
Participant
@markcostello1
EXCELLENT!
19 February 2019 at 23:02 #397077
Nick Hulme
Participant
@nickhulme30114
It's a significant geometrical compromise and not a very clever way to use a dual taper collet.
19 February 2019 at 23:44 #397081
Michael Gilligan
Participant
@michaelgilligan61133
Posted by Nick Hulme on 19/02/2019 23:02:12:

It's a significant geometrical compromise and not a very clever way to use a dual taper collet.

.

Admittedly, ignoring the front taper is a novel way to use a dual taper collet

… I wonder what the internal profile of the soft jaws might be.

It does, however, seem a neat way of holding thin tubes in a hefty 3-jaw.

MichaelG.
19 February 2019 at 23:50 #397082
John McNamara
Participant
@johnmcnamara74883
I beg to differ.

The workpiece is a thin wall tube, while it would be easy to make a special set of soft jaws to hold the part, using this method will allow an easy change to a wide range of sizes.
The chuck itself is fitted to a high end CNC machine, I am guessing that the the hydraulic chuck body is very high accuracy and that the soft jaws were bored in situ dead true.

I have always suspected the ER system's main flaw is that the front taper is centered by a screw cap. I have seen a number of experienced machinists videos that show the cap being given a smart tap with a soft hammer to improve the centering of the cap.

I think this is a good solution, Looking at the other videos on the site it appears the shop produces a lot of differing small parts.
Does it produce parts that are within spec efficiently? that is the only question that needs to be answered.
20 February 2019 at 00:08 #397085
Michael Gilligan
Participant
@michaelgilligan61133
Posted by John McNamara on 19/02/2019 23:50:10:

I beg to differ.

… hopefully from Nick, not me

MichaelG.
20 February 2019 at 00:25 #397086
John McNamara
Participant
@johnmcnamara74883
Yes Michael I was responding to Nick.
20 February 2019 at 01:26 #397090
Paul Lousick
Participant
@paullousick59116
Holding something in a collet has normally been more accurate than using a 3-jaw chuck.

This a 3-jaw holding a collet. How accurate is that ?

Paul.
20 February 2019 at 06:28 #397094
Neil Lickfold
Participant
@neillickfold44316
Hey John, I like it. That is quite a trick setup , especially the fact that the chuck has a limit on the opening.

As for accuracy I am sure it is better than 0.01mm if the collet is a precision collet. For it's application with full contact engagement in the collet looks really good to me.

It would also lend itself to the use of distortion collets as well. Very interesting.

I might have to make up a set of jaws to allow this to happen.

Neil
20 February 2019 at 07:04 #397097
JasonB
Moderator
@jasonb
Michael if you follow John Mc's link to teh FB page you can see the jaws have a tapered cone turned into them and small lip to retain collet via it's groove.

Like Nick I wonder how that can apply an even force all around the collet rather than just give 3 points of contact which would be more so the further the collet was closed down. At best it spreads the load more than using standard 3-jaws and saves having to make dedicated soft jaws for each size.

Edited By JasonB on 20/02/2019 07:26:23
20 February 2019 at 07:53 #397100
Michael Gilligan
Participant
@michaelgilligan61133
Posted by JasonB on 20/02/2019 07:04:15:

Michael if you follow John Mc's link to teh FB page you can see the jaws have a tapered cone turned into them and small lip to retain collet via it's groove.

.

I avoid FaceBook as much as possible … but that ^^^ is exactly what I surmised when responding to Nick.

MichaelG.
20 February 2019 at 08:05 #397101
JasonB
Moderator
@jasonb
Posted by John McNamara on 19/02/2019 23:50:10:

I beg to differ.

The workpiece is a thin wall tube, while it would be easy to make a special set of soft jaws to hold the part, using this method will allow an easy change to a wide range of sizes.

Reading some of the comments and replies he says "it is important that the jaws are machined to the collets CLOSED size" so unless you are only holding work at the upper end of the collets range you would need a rebore of the jaws every time eg if holding 1/4" stock in a 7mm collet so can't see that being any quicker or easier than machining soft jaws.
20 February 2019 at 08:24 #397104
Mike Poole
Participant
@mikepoole82104
It sounds as though this works but in very qualified situation for a very specific purpose. This is not an alternative ER chuck but a special purpose tool utilising an ER collet. Worth filing for reference and may be a seed for other applications. Interesting.

Mike
20 February 2019 at 08:37 #397107
Martin Kyte
Participant
@martinkyte99762
Looks like it would be optimum for a fixed diameter only.

regards Martin
20 February 2019 at 08:47 #397110
Martin Kyte
Participant
@martinkyte99762
Are the jaws air operated ?

Martin
20 February 2019 at 08:49 #397111
Neil Wyatt
Moderator
@neilwyatt
My thoughts are:

For small bore collets which are counterbored, ideally you need more compression at the front.

It prioritises convenience over accuracy. On my lathes changing chucks takes about as long as changing jaws, but that may not be the case for this hefty machine with six mounting screws.

Neil
20 February 2019 at 08:55 #397113
JasonB
Moderator
@jasonb
Again if you read the link he says changing the 3-jaw to a collet chuck takes a long time so quicker for him to swap jaws.
20 February 2019 at 09:15 #397117
Martin Kyte
Participant
@martinkyte99762
I think if you have a cnc machine with an air operated 3 jaw chuck then with the addition of 3 special jaws you have an adaptor to take the full range of ER collets and can safely hold thin walled tube. Not a bad result for not much outlay.

regards Martin
20 February 2019 at 09:40 #397123
jann west
Participant
@jannwest71382
also worth noting that this setup would allow the easy integration of a depth stop through the back-end of the headstock spindle … something typically considered an advantage of the 5c over the ER collet.
20 February 2019 at 09:54 #397126
Joseph Noci 1
Participant
@josephnoci1
Would there not be a chance of swarf, minute or otherwise, penetrating the collet/jaw contact area when the jaws are released to remove the work piece? After all, the swarf flies everywhere inside the cabinet and in the video, the tiny brass shavings might enter the chuck area. Unlike a normal collet holder that is essentially sealed except for the slots at the workface.

I still like the idea though. I also especially like the cnc machine..

Joe
20 February 2019 at 10:01 #397129
JasonB
Moderator
@jasonb
He says he uses through coolant collets so slots are sealed
20 February 2019 at 10:45 #397133
jimmy b
Participant
@jimmyb
I just used to hold an ER collet chuck in some soft jaws.

I really can't see an advantage to how this is shown.

JIm
20 February 2019 at 10:45 #397134
Chris Trice
Participant
@christrice43267
Given the high degree of accuracy with which the chuck jaws are obviously machined, I can imagine that the part of the jaws that fits in the collet groove also contact the bottom of the collet groove and participate in the closing action as well as preventing the collet being squeezed out the chuck..
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