Core One INDX Tool Holder Tapping Helper

While waiting for my Core One INDX conversion kit (non-FE) to arrive, I've been reading the forum and noticed that quite a few people have broken the tool holder whilst tapping the two holes. One possible reason for this is not making sure that the screw is square onto the holder whilst tapping the holes.

This is a small jig to fit onto the tool holder to ensure that the holes are tapped square.

When assembling the Core One Tool Holder, assembly instruction 5.68 has you use M3x12cT screw to tap the two holes on the holder. When using this jig, use M3x25 screw and tighten it the full length of the screw making sure not to over tighten.

I have only confirmed this on 'replacement' tool holders that I have printed while waiting for my INDX conversion kit to arrive.

EDIT:  22/07/2026: For those of you with the FE version that have a rough surface in the screw hole, I have added a new version where the protrusion is 1mm smaller. Hopefully this will give a better fit. Please let me know if this is better or still needs to be smaller.