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ER32 Collet?

3/4" required

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Bo'sun04/05/2021 17:22:59
621 forum posts
2 photos

Good evening all,

I need a 3/4" ER32 Collet. Can anyone recommend a reliable source? I say "reliable", because some sources seem to think a 19mm collet will suffice, but it's 0.05mm too small.

I had been led to believe that a 20mm collet would close down to 19mm, which in theory may work, but talking to the kind people at ARC, they don't recommend it.

Emgee04/05/2021 17:36:02
2446 forum posts
291 photos


old mart04/05/2021 17:36:34
3912 forum posts
268 photos

This firm advertises imperial er32 collets, they are better than the ebay lottery.

Pipped at the post by o



Edited By old mart on 04/05/2021 17:38:08

Oldiron04/05/2021 17:39:31
997 forum posts
40 photos

Try :-

Gloster Tooling Supplies Limited

Address: 52 Pinewood Road
Fax number:01452-72921
I have bought imperial & Metric colletts from them and had good servise.
I got my oversize ER32 Colletts from them at a good price also.
Bo'sun04/05/2021 17:57:13
621 forum posts
2 photos

Thanks for the info',

Tried Protool yesterday, but they're out of stock. I'll give Gloster a try this evening.

Andrew Moyes 104/05/2021 18:29:58
148 forum posts
23 photos

I have a Vertex set of metric ER32 collets. They are more expensive than the run of the mill Chinese collets and are supposed to be of better quality. The 19-18 collet is also marked 3/4" so they are not worried about the extra 0.05mm. Opening it up that extra small amount will stress the collet less than closing down a 20mm collet almost a full millimetre but in theory that should be okay too.

Mark Rand04/05/2021 19:40:31
1315 forum posts
38 photos

I happily use Rotabroach cutters (3/4" Weldon shank) in a 19mm ER32 collet. The one caveat, in this case is that I made a 3/4" top-hat shaped pin to go in the small end of the collet as the Rotabroach cutters aren't the full length of the collet. This forces the collet to close parallel.

Vic04/05/2021 21:34:13
3092 forum posts
16 photos

Given the amount of spring in the collet I’m pretty sure you’d get 3/4” stock into a 19mm collet. If your 3/4” stock is over size it likely won’t fit either if it’s too far over.

Bo'sun05/05/2021 07:29:01
621 forum posts
2 photos

Tried Gloster Tooling as suggested, but nothing in their Ebay store. Thought I'd ask them anyway, and I'm awaiting an e-mail reply. As it's for an End Mill, I'm tempted to try a 19mm collet.

As Andrew say's, opening up 0.05mm will probably put less strain on the collet than closing it down 1.0mm.

SillyOldDuffer05/05/2021 09:02:10
8906 forum posts
1999 photos
Posted by Bo'sun on 05/05/2021 07:29:01:
.... As Andrew say's, opening up 0.05mm will probably put less strain on the collet than closing it down 1.0mm.

I've read putting anything too big into an ER32 collet damages it and think the danger is real.

Collets fit snugly into a cone inside the chuck and are compressed down from fully open. If 'fully open' is forced wider by ramming an oversized object into the collet, the collet expands and won't fit the cone properly. If the operator squeezes the misfitted collet hard by tightening up with a spanner, he could permanently bend the collet. If that happens, the collet is ruined. Dostorted collets can't grip anything properly.

I doubt the operating range stamped on ER collets is highly accurate. The dimensions are nominal. My metric set accepts maximum size diameters as a light push fit, which means the collet must be slightly oversized. How oversized an ER collet can be doesn't seem to be covered by the specification, so I guess some are more generous than others. All that can be said is that 19mm collets will take 19mm diameter shafts. The latitude would allow a penny conscious collet maker to sell 3/4" collets as 19mm. A 19mm collet might take 3/4" (19.05mm) or not, but if it's been sold as 3/4" it's probably OK.

If a 3/4" shank fits gently into a 19mm collet, it's good to go. If it's unwilling, don't force it.


Circlip05/05/2021 09:45:18
1531 forum posts

Collets? For milling cutters, Autolock or Weldon, For turning, fully adjustable, Rubberflex OR four jaw.

Regards Ian.

Andrew Moyes 105/05/2021 10:06:45
148 forum posts
23 photos

Here is the evidence. It's a nice sliding fit on 3/4" stock.


Tony Pratt 105/05/2021 10:13:36
2033 forum posts
12 photos

Autolock milling cutters are so last year, I used them when we had nothing else but it's now R8 or ER collets for me. For the lathe I use what is most appropriate, depends on the work but mainly 3 jaw or again ER collets, 4 jaw when necessary.


Bo'sun05/05/2021 10:13:52
621 forum posts
2 photos

Thank you Andrew, where did you get it from?

Andrew Moyes 105/05/2021 10:20:42
148 forum posts
23 photos

Bo'sun - Rotagrip in Birmingham sell the Vertex collets.

Mark Rand05/05/2021 11:46:44
1315 forum posts
38 photos
Posted by Circlip on 05/05/2021 09:45:18:

Collets? For milling cutters, Autolock or Weldon, For turning, fully adjustable, Rubberflex OR four jaw.

Regards Ian.

It's a bugger for someone without a surface grinder to put a Weldon slot or Autolock thread on HSS or carbide endmills.


Edited By Mark Rand on 05/05/2021 11:52:15

not done it yet05/05/2021 13:15:11
6889 forum posts
20 photos


I would be interested how you thread with a surface grinder, please.

Bo'sun05/05/2021 13:16:44
621 forum posts
2 photos

Mmm........ I wondered that.

Mark Rand05/05/2021 15:36:53
1315 forum posts
38 photos
Posted by not done it yet on 05/05/2021 13:15:11:


I would be interested how you thread with a surface grinder, please.

The same way that you thread grind with a Quorn grinder:-

Arrange a master thread and follower/chaser. The master thread is on a sliding+rotating mandrel which also holds the workpiece. As the workpiece is rotated, the master thread moves the mandrel+workpiece axially. With a correctly dressed wheel and correct alignment a thread results.

This could be useful if one insisted on using Clarkson Autolock cutters, since the thread for all sizes is 20tpi,#

Note you still need to grind a centre on the endmill if is doesn't already have one. That's a much more specialised bit of kit...

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