Old lathe, chuck accuracy

Edited By Chris Trice on 19/04/2010 00:38:17

Hi. I think that it was geometers articles published in ME some years ago that gave details on how to true up the chuck jaws (they can be found on this site and the internet), anyway I trued up my worn Bernerd chuck useing his method, which shows how to clamp the jaws.

My chuck has three extra holes at the front which I drilled right through and spotted on to the back plate then drilled and tapped these, then locked a small piece of hardwood in the jaws 20mm diameter which is about the average size.

Put threaded rod through the three holes and then clamped the jaws solid with three pieces of steel plate, you could use engineers clamps instead, that, kept the jaws in the right position, so that I could drill out the wooden block,  then useing a cheap Dremel grinder SLOWLY rotated the chuck by hand, I used the largest grinding wheel I had, BUT the collet holder in these cheap grinders is rubbish it let go.!!!!! I never found the wheel again as it bounced around the workshop, Good workshop practice or what ????.  I only took off the minimal of the most worn jaw but had to take off 5-6 thou off the others, the wear was mostly at the front. Now at 20mm diameter the DTI shows virtualy no run out, as previously mentioned old worn chucks give different readings at other sizes, you can get them refurbished but its cheaper to buy a new one.

Swarf is good swearing at it is not.

John Holloway

Edited By NJH on 09/10/2011 18:47:40

Edited By NJH on 09/10/2011 18:48:31

I thought that was the case Norman but as a beginner I just wanted it confirming by somebody more experienced. My suspicions were raised after reading quite a few articles by Harold Hall where after turning in the 3 jaw, any swapping round and the workpiece was then transferred to the 4 jaw and clocked.

Edited By David Littlewood on 09/10/2011 19:36:23

Edited By mick H on 09/10/2011 19:53:03