Thanks Chuck for the reply.
There is enough room for 6mm of keep plate and the heads of the socket screws, so I suppose it would be possible to have two 3mm plates and grub screws with locking nuts to apply pressure as per the slide gibs¡
The other idea I had was to mill a very shallow rebate in the new keep plates (as you did, leaving the portion that makes contact with the bed) and then shim them back up with feeler gauge material until the fit is good. Metric feeler gauges have a useful range going from 0.05 mm (I¡¯ve just ordered four!).
It did strike me (while I was lying in bed of course) that the other thing that could cause this was if the bed was bent, slightly arched - the middle of the carriage would be pressed down on the bed but there could be a gap (and thus play) at the outer edges. So I¡¯m assessing the beds of my two U3s. One (in bits already) is flat but ever so slightly twisted according to my surface plate. I can just get the 0.05 mm feeler gauge under the corner. I don¡¯t think that¡¯s enough to cause an issue.?The other U3 is being dismantled.
