This is a simple jig, you set the adjustable legs to the height of insert required and lock insert in place on the bolt & screw. I remove material from the non-lead end of the insert.
Run this across a metal file and once all the legs touch the base it should be the correct size.
I did try this with sandpaper but it needs to be harder than the sandpaper.
There are 4 holes, 1 each for M3, M4, M5 and ¼-20 threaded inserts.
To use you need;
4 x M5 threaded inserts
4 x M5 Hex head bolts
5532943_Handles_for_M3_to_M6_bolts_and_screws from Thingiverse (Remi-Rafael)Optional
All or whichever one you need, 1 of each of
M3 thread insert
M4 thread insert
M5 thread insert
¼-20 thread insert
The author marked this model as their own original creation.