In his book on wheel and pinion cutting, Mr. Wild uses some very interesting and useful tools.
I have started to replicate some of them, adapted for use on a Sherline.
Here is a support tool that fits in the adjustable tailstock holder.
It can be locked with the screw for milling or cutting or left free to revolve (with lube) for turning. Take the tommy bar out first though!

This is it partly disassembled.

I will post pictures of other tools as I make them.
Steve