In GHT's book, page 198, Fig 21.1 he shows the disc held to the faceplate by that stepped spigot with nut and stud arrangement. It necessitates having drilled and bored the hole in the middle of each plate beforehand. Plus each plate would need to be set up to run concentric using a dial gauge. The wood is held to the faceplate by screws, although he says they are not necessary. This all seemed a bit dodgy to me so I also drilled the three countersunk screw holes in the centre of each plate plus a forth indexing hole he specifies and made an arbour to mount the plates on, using the little plug/ring jig he illustrates on page 190. I made that jig by direct indexing with the spring loaded plunger engaging with the teeth on the 60T gear. The arbor was held in the chuck on the VDH. No faceplate involved.

From memory I drilled the first plate with 60 holes using direct indexing on the 60T gear teeth, although I may have used his method and made a one-hole plate first and used one full turn of the handle for each division.

Either way, I shall never forget drilling all 811 of those holes, then deburring both sides of them.

Almost as much fun as trepanning the three discs out of flat plate from the local builder's supply yard. Just like parting off — only on a curve.

So it was faced, bored and then trepanned in one setting so I had the hole in middle for mounting on the arbor above.

Edited By Hopper on 17/02/2021 06:33:25