I have this decent (Rohm) 5/16" keyless drill chuck. A few weeks ago I put it on the mill and found that it had developed highly noticeable runout …. the kind of runout that I couldn't have missed previously. I'm careful with this chuck and certainly don't recall any serious accidents. I just checked the runout as follows:

The runout on the spindle and on the arbor shank (point A) was negligible. The runout on the chuck at point B (measured with a centre drill installed) was 0.02" TIR.

The chuck is tight (very) on it's Jacob's Taper arbor and in the absence of any severe handling – which I swear it hasn't had – I don't really know what would cause this to suddenly occur.

– notwithstanding the tightness of the fit on the Jacobs Taper I'd like to remove/refit it (and perhaps check the runout of the JT vs the shank) does anyone have a recommendation for getting these apart (without being rough on the chuck of course).

– Any other suggestions as to what might have caused this?

Edit: just noticed that the leader-line from The 'B' label seems to have gone walkabout. Just imaging a horizontal line from 'B' to the chuck body.

Edited By Bandersnatch on 15/04/2017 01:03:14

Spurry – they look handy. I'll look around on this side of the pond …. or perhaps I could make something.

Roy – yes, I probably should have done – and would have done if I'd been looking for a precise value – but I was only after a ball-park.