I decided yesterday to fit a new chuck that had been sitting around for some while to a spare backplate, and reduced the backplate diameter and register to fit the recess in the back of the chuck. At this point, as this chuck is of the kind that has 3 blind threaded holes at the back for the mounting bolts, the question arose as to how to (quickly) mark out the backplate for the 3 holes. Marking out the first was easy enough, move a sharp lathe tool to 1/2 of the PCD, use it to lightly score a PCD circle on the backplate, centre pop and drill the first hole, easy peasy. But short of messing with a rotary table (still not sure which box to look in since the move!), what about the other 2? At this point, as has happened often over the years, I remembered a tip that came from one of my many phone conversations with John. Machine a sharp point on a short length of threaded rod (or a length cut from a spare matching bolt) and thread it into one of the threaded holes in the back of the chuck, leaving the point sticking out and enough thread to grab onto to remove it later. Offer up the backplate, sight through the first hole to one of the empty threaded holes in the chuck, give the backplate a light tap where it touches the pointy bit, rotate the backplate 1/3 of a turn to sight through to the other empty hole, another light tap. You now have a rather blunted pointy bit but enough of a mark on the backplate in the other 2 drilling positions so you can make decent pop marks and drill the last 2 holes.