Clarkson Autolock – Excessive Runout

[Graham WhartonParticipant @grahamwharton]

Hi,

I have got 2 Clarkson Autolock Chucks (One S Type Small, and One S Type Large). They are both on an MT3 taper.

They were both from ebay, and I didnt really pay much for them. I dont use them as my primary chuck, I use an ER32 collet chuck for that.

I got them for a few reasons, to allow me to mill using larger cutters than my ER32 will hold, and also as a second chuck in the mill, if I am workholding in the rotary table using the ER32.

So, the question. What are other peoples experience on the accuracy of Clarkson Autolock Chucks. I measured runout on the Large chuck of 0.3mm !!!!!!. Its so bad it makes my mill vibrate. Runout on the smaller one is 0.1mm. If I make the same measurement on my ER32 chuck I get no needle movement on a 0.01mm DTI. The same applies for spindle runout on the MT3 taper about 1cm up inside the spindle taper from the base, no movement on the needle.

I have done the usual tricks of making sure the spindle taper is clean, and also ran fine emery over the morse taper shanks on the two clarkson chucks.

Have I just been really unlucky here and managed to pick up two aweful examples from two different sellers that have taken some serious abuse?

What was the quoted accuracy on these things when new?

Is there any way to salvage these chucks. Straighten them somehow?

Or maybe reverse chuck them in a 4 jaw in the lathe and centre according to the chuck head, and then re machine the taper? Would there be a better way of holding these for remachining of the taper….. I'm thinking of using some sort of extended female centre in the headstock that mates with the centre inside the chuck, but then what about the tailstock end….. I'm just thinking aloud here. Would love peoples comments.

It seems a shame to bin these, when I have a full set of imperial and metric collets for them and a large number of threaded shank cutters.

[Graham WhartonParticipant @grahamwharton]

[KWILParticipant @kwil]

Have you clocked the innner ground surface of the collet holder and measured the run out there?

[Graham WhartonParticipant @grahamwharton]

Yeah, I was measuring on the inside ground surface, and also on the shank of a cutter installed in the chucks. Same runout measured give or take a few thou.

[KWILParticipant @kwil]

As you have a ER32, lock a suitable piece of ground steel in the Clarkson, say 0.625" dia. and then hold that in the ER32, Clock the taper. If the collet and Clarkson head are OK then you should only have the taper error?

Edited By KWIL on 14/04/2012 18:52:09

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