Scratch building often requires assembly and disassembly of parts, initially to check fit and function, then for painting. Bolts screwed directly into plastic are risky because the plastic threads are weak. In circumstances where assembly/disassembly may be needed several times, or where a tight assembly is required, threaded brass inserts glued into the plastic are preferable.

Click on the button to download a two page PDF document that describes how to make inserts for 1.0 mm, 00-90, 0-80, 1-72 and 2-56 bolts.