John,

I have only used the S type, but … a few seconds searching on Google located this thread from 2006, on another forum.

MichaelG.

John – my Centec came with a Clarkson Autolock chuck – but after close to 20 years of owning the mill, and never using the Clarkson chuck, I gave it away, and use ER 25 collets almost exclusively. ("over here" at least, the screwed shank end mills are very hard to find and pricey, and I try and do everything in metric, so the autolock chuck was of no use to me)

Sorry, no help I'm afraid!

Another John.

I used these older Clarkson chucks during my apprenticeship (1958/1964),procedure was as follows and everyone in the factory worked this way, slip the collet in the sleeve,push sleeve and collet into the chuck body ,screw cutter into the collet until the the screwing action starts to push the sleeve out of the body,the sleeve should move by about 1/32 on an inch,then screw the nut on by hand.do not use spanner. everyone was warned to let the sleeve move out a little and do not use a spanner or will be a b—— to remove the cutter,these instructions are not the same as the later auto locks and thats where the confusion and disagreements started over how to use the later types. The modern ER collets are good I have some to hold taps in the tailstock,but a ER will slip if pushed too hard particularly on the bottom end of the 1 mm range,,a Threaded Clarkson will not pull out or slip,essential when machining say a keyway in tough material,and the keyway must have constant depth.

I've heard this concern from others, but I've personally never had an ER slip.