Clarkson Autolock S Type Chuck

Hello, got a small Clarkson Autolock S type chuck with my recently acquired VM-30.

Clarkson advert says it comes with 4 collets 'to accomodate cutters with 1/4", 3/8", 1/2" and 5/8" (or 6, 10 12, 16mm) diameter shanks'. There were 4 collets in the box with the chuck.

Also came with a cutter marked as 16mm the shank measures 15.98mm which fits well to the largest collet.

My query is, does one set of 4 collets cover the imperial and metric sizes or are there both imperial and metric sets and I just happen to have received the metric set?

Hope this makes sense. Sorry if is an idiot question, cheers, Dave.

There are two separate sets of 4 collets for metric and imperial; looks like you have the metric set.

Andrew

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

Andrew and Graham: excellent replies thank you. The three larger collets are in good order but the 6mm one won't slide easily into the lower part of the autolock chuck; seems to have been damaged somehow perhaps by a 1/4 inch shank being hammered in. However GandM Tools have spares so have ordered a couple today.

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

Only one problem, if you follow the official method, but with a small dia cutter, you may quickly find why the other method is used as well!!

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

Next to last paragraph.

If cutter turns in the chuck under the effect of cutting forces, the split collar 'C' is forced into the taper seating of sleeve 'B', thus increasing the grip on the shank.

And that folks is the reason you will not see Clarkson collet chucks in workshops today and why the ER series has overtaken them.

For one you are not tied down to trying to obtain the cutter of choice in material of choice with a thread on.

Secondly that 'self tightening' will stuff up any tool length off sets you have set in a tool table.

Thirdly many cutters today are made with the shank equal to the cutter diameter 4mm and 5mm are two of the most popular ones to save expensive material but the Clarkson still relies on 4 collets per set.

If you 'have' to use a Clarkson holder for any reason on a CNC then you need to insert the cutter with a slight gap between the nut and keep that gap even after tightening. It's the only way you will be able to keep the depth of cut you program.

Personally I'm glad to see them fall out of use, the ER series if far more popular and adaptable. I do have one holder and that's a 4:1 speed increaser that has a Clarkson chuck built into it and I use it to hold one of the small ER11 collet chucks from ARC with the Clarkson adaptor on the end so I can hold various size drills from 1mm up to 3.2mm for special jobs.

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?

Hello Rod,

I have a Clarkson holder for my Senior mill and three Titanic chucks for my Denford Triac (similar principle), they give me excellent service, I would be sad to lose them.

Regards,

Michael

.

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

It is 'just possible' to fit one size of, I think, imperial shank into the corresponding metric collet which wrecks it by splaying the jaws. I cannot remember the precise combination, but it is important to check like with like and not assume all other combinations are No Go.

regards Martin

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

Neil

Trying to fit a 16mm cutter into a 5/8" (15.875mm) collet is most likely. For those with man size chucks trying to fit a 32mm cutter into a 1-1/4" (31.75mm) collet is also an issue; especially as my larger collets are not Clarkson, but Dormer, and do not have the helpful distinguishing groove on the lugs.

Andrew

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

Rare but occasionally you find one...

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.

You can also get FC3 adaptors. Mine has rarely been used and looks like it's in need of some TLC.

regards Martin