Drill Chuck Runout

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

Hmm - always the way - having posted that and looked closely at my own picture, it looks to me as if that spline at the top has moved out. I thought at first that was its normal position but having checked some pics at the Rohm site I think it may have shifted. I'll try pressing it in tomorrow.

To break the taper just get yourself some Chuck Removal Wedges, sized for the taper.

One example from Arc

**LINK**

Pete

For the B measurement I would have gripped something in the chuck rather than use the chuck body

Roy

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.