ER32 collets

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ER32 collets

This topic has 17 replies, 9 voices, and was last updated 31 March 2021 at 20:43 by DC31k.

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30 March 2021 at 18:06 #537136
Bo’sun
Participant
@bosun58570
Good evening all,

Any thoughts on the minimum clamping length for an ER32 collet? I would like to hold a length of 3mm.

Will it damage the collet if it's too short?

I did think of another piece the same size towards the back of the collet, but wasn't sure.
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30 March 2021 at 18:06 #20223
Bo’sun
Participant
@bosun58570
Minimum clamping length?
30 March 2021 at 18:36 #537141
Martin Kyte
Participant
@martinkyte99762
I would say the shortest length was the length of the collet but it depends what you are doing and how tightly you wish to hold the piece.

regards Martin
30 March 2021 at 18:36 #537142
old mart
Participant
@oldmart
A backup would be better than nothing, but everything depends on the diameter held, 3mm would be better than larger and clamping 6mm would be risky.
30 March 2021 at 18:37 #537143
Michael Gilligan
Participant
@michaelgilligan61133
Quite simply … it won’t clamp properly unless you do put that extra piece at the back

ER uses a double taper to do ‘parallel’ clamping … leave one end empty, and it doesn’t !!

MichaelG.

Edited By Michael Gilligan on 30/03/2021 18:40:01
30 March 2021 at 20:45 #537170
old mart
Participant
@oldmart
You would think that the parallel clamping feature would mean that the collets always had one diameter right through. I have some er25 collets with only half the length at the nominal size.
30 March 2021 at 21:56 #537178
Michael Gilligan
Participant
@michaelgilligan61133
Posted by old mart on 30/03/2021 20:45:23:

You would think that the parallel clamping feature would mean that the collets always had one diameter right through. I have some er25 collets with only half the length at the nominal size.

.

Well, actually … I wouldn’t

It’s a parallel clamping action, generated by the tapers and the slots

… the internal profile is trivial

MichaelG.
31 March 2021 at 07:32 #537199
Nicholas Farr
Participant
@nicholasfarr14254
Hi Bo'sun, my ER32 collection of collets only go down to 6mm, I use one of these ER11 collet chuck gripped in a 16mm collet to do smaller stuff and these collets are about 18mm long, although my 6mm ER32 collet has only 23mm that actually does the gripping. These collet chucks also give me much more room and easier to see where the tool is, when holding small cutters on my mini mill.

Here's an example of how much easier I find it using a ER11 collet chuck with a small cutter, on my mini mill, the ER11 is held in my normal collect chuck that is used on this mill.

Regards Nick.

Edited By Nicholas Farr on 31/03/2021 08:01:03
31 March 2021 at 08:11 #537201
Sandgrounder
Participant
@sandgrounder
Posted by Michael Gilligan on 30/03/2021 21:56:59:

Posted by old mart on 30/03/2021 20:45:23:

You would think that the parallel clamping feature would mean that the collets always had one diameter right through. I have some er25 collets with only half the length at the nominal size.

.

Well, actually … I wouldn’t

It’s a parallel clamping action, generated by the tapers and the slots

… the internal profile is trivial

MichaelG.

I'm not saying you're wrong it's just that I'm also having trouble visualising it, say a 12mm collet is being closed on a short length of 12mm shaft by the tapers, once the collet clamps onto the shaft it can't be closed further and everything stays parallel, both the internal 12mm diameter and the tapers, even clamping on to a 12mm ball would prevent further closing of the collet in its taper, I do realise that the longer length that is in the collet the greater the holding power will be for milling cutters etc.

John
31 March 2021 at 08:22 #537202
Tony Pratt 1
Participant
@tonypratt1
In theory yes the collet should grip on a short length but in practice the rear portion will continue to collapse & you will get a 'bell mouthed' condition on the collet.

Tony
31 March 2021 at 09:18 #537217
JasonB
Moderator
@jasonb
As Tony says in practice the back of the collet just collapses. For anyone in doubt you can try this at home.

10mm collet, 10mm HSS blank inserted 3mm into collet and just nipped up by hand no spanners, that is a 9.4mm drill sticking out the top which won't enter the back of the collet.

Edited By JasonB on 31/03/2021 09:18:36
31 March 2021 at 09:22 #537218
Bo’sun
Participant
@bosun58570
Thanks all,

I'll use a back-up piece towards the back of the collet as suggested. Clearly it will increase the clamping pressure and life of the collet.
31 March 2021 at 10:03 #537229
Michael Gilligan
Participant
@michaelgilligan61133
Posted by Sandgrounder on 31/03/2021 08:11:54:

Posted by Michael Gilligan on 30/03/2021 21:56:59:

Posted by old mart on 30/03/2021 20:45:23:

You would think that the parallel clamping feature would mean that the collets always had one diameter right through. I have some er25 collets with only half the length at the nominal size.

.

Well, actually … I wouldn’t

It’s a parallel clamping action, generated by the tapers and the slots

… the internal profile is trivial

MichaelG.

I'm not saying you're wrong it's just that I'm also having trouble visualising it, say a 12mm collet is being closed on a short length of 12mm shaft by the tapers, once the collet clamps onto the shaft it can't be closed further and everything stays parallel, both the internal 12mm diameter and the tapers, even clamping on to a 12mm ball would prevent further closing of the collet in its taper, I do realise that the longer length that is in the collet the greater the holding power will be for milling cutters etc.

John

.

I think we may be ‘on different pages’ , John

Tony and Jason have addressed your point nicely … but my comment was a specific response to ‘old mart’

i.e. The internal shape of the collet’s bore is trivial when understanding the closing action of the collet.

…. the ones with stepped bores obviously ‘get away with it’ when there is sufficient length being gripped in the larger bore, but I wouldn’t trust any collet to reliably grip a 3mm insertion length. [which is, I think, what Bo’sun was contemplating] unless the material was less than about 1mm diameter.

MichaelG.

Edited By Michael Gilligan on 31/03/2021 10:11:27
31 March 2021 at 11:51 #537238
Martin Kyte
Participant
@martinkyte99762
Bang on regarding the comments about the closure of the collet. Until the bore is filled it will collapse in a parallel fashion. However the tapers are of different angles the rear being slower than the front. Intuitively you would think that for a full length bore on a cylindrical workpiece/tool that is longer than the collet that it would hold the back portion tighter than the front for any given closing torque. How the dynamics of optimisation to get an even clamping force on the two halve works is beyond me especially when you consider friction and stiction but the parallel length of the rear cone will make a difference. There is also the issue of releasing the collet. Most of mine seem to wedge in place when released and require the active pull out achieved by unscrewing the nut at which point the collet pops out with a bang. The wedging action can only be on the rear cone as the nut taper is no longer in contact at this point. Maybe a releived portion of the bore at the back helps, I don't know really. I've only just begun to think about it.

regards Martin

Edited By Martin Kyte on 31/03/2021 11:52:41

Edited By Martin Kyte on 31/03/2021 11:53:23
31 March 2021 at 16:20 #537262
old mart
Participant
@oldmart
When thinking about clamping a 3mm cutter in an er32 collet, it is unlikely that the shank of the cutter would be as long as the collet.
31 March 2021 at 16:24 #537263
Martin Kyte
Participant
@martinkyte99762
Posted by old mart on 31/03/2021 16:20:30:

When thinking about clamping a 3mm cutter in an er32 collet, it is unlikely that the shank of the cutter would be as long as the collet.

Maybe you should use a more suitable series then.

regards Martin
31 March 2021 at 19:28 #537322
Sandgrounder
Participant
@sandgrounder
Posted by Michael Gilligan on 31/03/2021 10:03:24:

Well, actually … I wouldn’t

It’s a parallel clamping action, generated by the tapers and the slots

… the internal profile is trivial

MichaelG.

I'm not saying you're wrong it's just that I'm also having trouble visualising it, say a 12mm collet is being closed on a short length of 12mm shaft by the tapers, once the collet clamps onto the shaft it can't be closed further and everything stays parallel, both the internal 12mm diameter and the tapers, even clamping on to a 12mm ball would prevent further closing of the collet in its taper, I do realise that the longer length that is in the collet the greater the holding power will be for milling cutters etc.

John

.

I think we may be ‘on different pages’ , John

Tony and Jason have addressed your point nicely … but my comment was a specific response to ‘old mart’

i.e. The internal shape of the collet’s bore is trivial when understanding the closing action of the collet.

…. the ones with stepped bores obviously ‘get away with it’ when there is sufficient length being gripped in the larger bore, but I wouldn’t trust any collet to reliably grip a 3mm insertion length. [which is, I think, what Bo’sun was contemplating] unless the material was less than about 1mm diameter.

MichaelG.

Edited By Michael Gilligan on 31/03/2021 10:11:27

Sorry about that Michael, I should have read the previous posts more closely.

John
31 March 2021 at 20:43 #537338
DC31k
Participant
@dc31k
Posted by old mart on 31/03/2021 16:20:30:

When thinking about clamping a 3mm cutter in an er32 collet, it is unlikely that the shank of the cutter would be as long as the collet.

Rego Fix show up to four different possibilities for the internal arrangement of ER collets. See

https://us.rego-fix.com/system/files/docs/2017-09/RFAG_TD_ER_Spannzangen-Masse_EN_0.pdf
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