That looks like an Autolock-style collet chuck designed to hold only the appropriate screwed-shank cutters – it won't hold a plain shank cutter.

May be wrong – just trying to interpret the images! The body looks as if it has a centre point at the back which is a key part of the holding mechanism.

On the other hand, with the right cutters, these are probably the most secure collet chucks you can get! There is a correct way to install cutters into these chucks, but let's make sure we know what we are looking at first.

The collets have a threaded bore to suit threaded shank tooling. They will not close down on a plain shank tool. You need something like this. The centre drilling fits over the point in the back of the collet holder.

Martin C

I don't think they can be like ER collets as they have a circumferential groove at the point where the front and back tapers join which engages with the eccentric ring in the nut. I agree that it looks more like an Autolock-type. An angled view of the back of a collet showing any internal screw thread would settle the matter.

Right! The thread is needed to make sure the collet is pulled hard against the internal taper. AFAIK Arc don't sell Pozilock though Warco do. Largely superceded by ER I think.

The big advantage with screw loc cutters is that they cannot walk out of the collet and they should self tighten. The disadvantage now is that they are out of fashion compared to fifty years ago and so the selection of cutters one can buy is less. Tracy tools also sell the cutters as do other suppliers.

As the OP has eight collets I assume he has a full set, both imp and metric.

Edited By elanman on 22/06/2023 21:53:19

Edited By elanman on 22/06/2023 21:53:41

It has crossed my mind that If I ever finish the Quorn (that'd be after starting it, of course ), then Prof Chaddock includes the concept of thread grinding. It'd be relatively simple to get a plated diamond Whitworth 20tpi form wheel made. Then parallel shank cutters could be threaded. Still have to put centre holes in them though.

I don't think the thread form needs to be so perfect that a modified angle would be required. I cut the threads until the collet threads on to the part loosely enough to ensure the self screwing action under load. It is important to polish the thread enough to reduce friction as well (a number of passes with Scotchbrite for example). This means that if the angle is slightly wrong you would just be cutting the thread slightly deeper to compensate. The important features are the diameter is correct and the centre drilling in the end is on centre. Mouse could do as I have done for a lot of tooling, modify (or get someone else to supply) an ER parallel shank collet holder to suit a 16mm collet if he wants to make use of this collet holder and collets beyond just buying threaded tooling. I have also centre drilled and cut the required thread onto, amongst other things, the shanks of a Ø16 insert milling cutter, a fly cutter and a set of "Little Hoggers".

Martin C

It occurs to me that threading carbide is probably not going to be as hard as drilling the centre in the end of it. There is also the risk of brittle threads in carbide shearing off. I would put carbide tooling in my modified ER holder or use my standard ER collet holder in the spindle.

Edited By Martin Connelly on 23/06/2023 08:39:55

Mouse, where abouts are you located ? If close to me in the Midlands I could give you a run through of using this type of set up.

Chris.

That nicely confirms what you have been told

MichaelG.

.

Edit: __ that’s probably stating the obvious, by now.

Edited By Michael Gilligan on 23/06/2023 09:49:46