There may be better ways, but after destroying half a dozen nozzles recently i needed a way of restoring them
I'll post some pictures later but briefly
Acetal seems to stick to the original nozzles Ok with Loctite 410 instant adhesive
The adhesive glued a No 2 nozzle back together after the whole cylindrical part was knocked off, and was back in use within 30 minutes.
where the damage was more extensive, I machined some 6mm bosses on some 8mm black Acetal
I drilled 6mm holes in the end of what otherwise would be scrap nozzles and glued the plugs in (with about 7 or 8 mm of 8mm Acetal projecting)
When it was et ( about 30 minutes) I chucked them up on my lathe (big Taylor chuck !) and machined them down
I didn't have a tailstock chuck that would take a 0.5mm drill, so I mounted the drill in a pin vice and put that in the tailstock chuck
A bit heath robinson, but the resulting nozzles work fine
I do have a little injection molding machine, and I'm very tempted to make a die to make them from scratch .. but have more pressing things to get on with ..