I have a Clarkson Autolock type S chuck which I aquired when I bought a secondhand Senior milling machine.  I couldn’t understand why small cutters weren’t revolving in a straight line until I found out that the HSS centre in the chuck had been badly mutilated, in fact about 1/8″ of the tip was broken off.  I have managed to remove the centre but have been unable to trace a spare one.  These centres are in solid HSS and the main problem with trying to make one is that the shank is conical so there has to be a fairish amount of precision during the manufacture, in other words it should be ground to fine limits.

So anyone know of a source of one of these, or another way around the problem?  The chuck is otherwise in good condition and I have a complete set of collets so would prefer not to have to “chuck it” away.

Hei Dave,

                     Thank you for the information.  I ordered a center yesterday!  I found out that the center cone is MK0 and obtained a lathe centre thinking that it would probabaly do the job.  It fitted Ok but then I realised that the flat seating was the stop point for the colletts and thereby critical lengthwise.  The MK0 protruded too much and I was intending to grind a little off the perifery such that the collets would sit properly against a shoulder, but time has been against me I’m afraid.  As Ian mentioned I could have produced one in silver steel and fiddled about to fit it properly, however, not having a piece of s.steel with a large enough diameter stopped the process, as trying to source this in Norway and obtaining a short piece is very difficult unless you want to buy 4 meters!   Anyway  – looks as though we have a good solution which is very pleasing.

Kind regards and thank you again – Antony

Hei Ian,

               I am actually very much aware of the Drill rod or sølvstål/kullstål as we say.  Unfortunately I don’t have anything suitable to “butcher” for this job, otherwise I would have started a long time ago.  There are however some little quirks to get by as you are probably aware of.  As the taper is MK0 then you really have to make an MK0 socket to fit in the collet chuck of the lathe (this just has to be concentric. It helps immensely if you have a MK0 lathe center to hand. I have tried to obtain an MK1 to MK0 adapter to remove some of the problems, but no go).  From here you can produce your MK0 taper to fit in the socket from the piece of material you have chosen. You can of course hone beforehand, but it is perhaps sensible to wait until you have the rest of the body finished, which has to be produced by holding it in the socket you have just made. It is also sensible to turn the part which the collett will back onto at the same time as turning the taper in order to have a method for testing trueness (that it doesn’t wobble!) when inserting it in your new socket.   The new center should maybe be made a little longer than necessary (it’s ok to take off a shaver, but putting on is a little more difficult).  When the center is finally finished you can take measurements in the body of the chuck after insertion.  A collet can be used to gauge the amount to be removed, because if you have made the center a little too long then the collett will protrude, and this can be precisely measured.  The it’s back to the socket you have made, insert the new center and turn to size.  I imagine that I would have used a couple days on this job, not because of it’s complexity but because my eyesight is getting rather poor, and even when using a head magnifier I get problems after a relatively short while.  SO, when the opportuniy comes up to buy one which fits instantly then I jump at it, as this saves a lot of hassle.

 

As a by the way, it used to be possible for me to hunt around in the metal collection bins at our lokal scrapyard (the council one).  This is now strictly forbidden and you risk a severe fine if you are caught.  This is of course another steback introduced by teh EEC. Norway isn’t a member but follows all of the rules and regulations religiously.

Regards – Antony