Colin,
I've split your post into Q) and A), easier for me.
Q) Is the main support pillar 1.25" diameter or is it reduced to a smaller diameter above the boss with the downwards projecting pin (pin used for adjusting radial position of the arm).
A) It tapers from 1.29/32 at the base down to 1.9/16 at the top where the 7/8"Ø bar fits into.
Q) Is the roller one piece with bearings and the conical shaped machined into it, or is it two loose cones (with or without bearings).
A) One piece, without bearings, the 1/2" shaft turned down to 1/4" for the roller.
![Excel Filing Machine Excel Filing Machine](data:image/gif;base64,R0lGODlhAQABAAAAACH5BAEKAAEALAAAAAABAAEAAAICTAEAOw==)
Q) What size bolts are fitted and are they in counterbores in the main boss.
Large boss – 3/8" Whitworth C'bored Small boss – 1/4" Whitworth not C'bored
Q) What is length of short boss that pressure finger or roller arm are fitted into.
A) 1.3/32"
Q) Is it just an optical illusion that the finger arm looks to be at an angle.
A) It's at 90° to the shaft.
Geoff – Audiobook next me thinks 🤔