A few general workshop machinery and other gadgets I have made over the years.
1 - The "sticky pin" made from a sketch in GHT´s MEWM.

Works beautifully.
2 - A lathe tool height setter, also from MEWM ...

Currently set for the MJ-189 but is easily adjusted to the C3. The underside of the pins are set at correct height, and by slanting them from above I get a scriber on center height as well.
3 - A pump center GHT style;

Only the spring left to do.
4 - A small micro tap handle. I found that especially small threads get better if they are cleaned up after initial threading using the same taps as for threading. It seems that the "swarf" sort of clogs the threads, and to work them I found that a small finger grip will ease this.

A simple alu turning with two M3 set screws to hold the tap (M2 in this case).
BR
/Peter