For quick identification, the metric ones have a groove cut round the base.

This is a metric collet

And this is an imperial collet

There are 4 in the metric set 6, 10, 12 and 16 and 4 in the imperial set 1/4", 3/8", 1/2" and 5/8" for the small S type chucks.

Actually there are 5 metric as you can also get an 8mm, but they are rarer than rocking horse sh*t and i've never actually seen an 8mm threaded shank cutter that would go in them.

Hope this helps

Graham

Did you get a copy of the assembly/tightening instructions with the chuck?

They are important and must be followed to get the best out of the chuck/ cutter assembly.

As a side note , I was taught the incorrect method during my apprenticeship at RR Shrewsbury in the late 70's and it was only about 15 years ago that I aquired a copy of the official instructions.

Here thay are (Just incase):-

Edited By Nick Hughes on 04/02/2015 19:47:50

The "Other method" on smaller cutters is almost guaranteed to burst the center hole in the cutter shank when the collar is nipped up!

First post ever, and questioning John Stevenson??? I must be crazy!

Surely the end of the cutter bears against the centre in the Autolock chuck. As the collet self-tightens, doesn't the collet itself move down into the taper in the closing nut, increasing the grip. The cutter doesn't move up, as it is constrained by the centre. No change in tool height.

Am I missing something?

.

My God son you have balls

Basically there is a difference in how tight you can screw a cutter up onto the centre point by hand and how tight cutting forces can screw it up.

On manual machines this is never a problem because usually you take a cut then measure, by which time the cutter is settled.

On a CNC you know the offset hight and expect it to go into the cut a pre programmed depth but when it does tighten up, that changes the depth and that interim cut where you take a measurement to enable the full depth to be applied is lacking as it's under computer control.

It does happen and when Clarkson's came out with their words of wisdom CNC's were either none existent or very rare so it was never a problem.

Once it did become apparent then people used 'the other method' which is not written down but has been achieved by experience.

Now don't get me wrong I'm not rubbishing Clarkson chucks, they are very good and one of the few where it's next to impossible for the tool to work it's way out.

The point I was trying to make is that their instructions cannot logically be applied to modern machining methods required by CNC.

If you are pure manual machining then TBH either way to tighten it works.

Some one mentioned small cutters but again look at this logically what will break first a threaded shank supported in a hardened sleeve or an exposed cutting edge , getting blunter by the rev with a length / diameter leverage of 4+ ?

Edited By John Stevenson on 05/02/2015 00:45:34

I would guess that forcing a 10mm into a 3/8" collet wouldn't do it any favours.

Neil

It's the thread that's the confuser. Most combinations don't fit but if you try screwing the collet onto it's opposite series (metric/imperial) cutter you will find that one size will go on metric and imperial.

As I said it's something to watch out for and not do.

As a user of the Clarkson Autolock system I do find the occational cheaper cutter that will not screw in freely due to badly ground threads. This usually is down to the crests being too sharp. A quick reduction on the offhand grinder with a diamond wheel seems to solve the issue.

regards Martin

Hopefully, the cutters you have will have their sizes marked on them. The metric ones require the metric collets and the inch/fraction ones, the inch size collets. The same rule applies to the Osborn Titanic type of collets.