Warning, rank amateur level construction ahead!
I made a simple detent for my old mini-lathe, which proved pretty handy for marking out holes on a circle in the absence of fancy gear, so decided to make one for the 'new' lathe:
1 Chose a 60 tooth gear (as it will give index positions for 2,3,4,5,6 holes) and loctited it onto a stub of steel (with a through hole) such that it can be removed if required in future 😀
2 Slid a rubber washer over the stub to create some friction against the adjacent spindle wheel
3 Cut a piece of metal to clamp to the square shaft that the changewheel cover slides onto. Chamfered the edge of the plate so it fits better between the teeth.
4 Turned up another stub of steel with a shoulder and through hole, to fit inside/against the mandrel nose.
5 Grabbed a piece of studding and a couple of nuts for either end

In use:
This is a manual operation so disconnect lathe from electricity supply!

Assemble the bits and mark off teeth to give the required number of positions (use tippex – shows up well and easy to remove). Clamp plate below first marked tooth, scribe using a scriber (set to centre height) in the tool-post. Unclamp, rotate chuck by hand to next position and repeat as required.
Add washers for a proper job and don't over-tighten the nuts.
