I've never had any success with plastic threads. If there's room to tap it out to a larger size, I do that - it typically takes about 2 minutes, if conditions are favourable. If there's not enough surrounding metal or the machine would have to be dismantled to do the job, I look for alternatives. Still, I don't mind wasting time when I feel in the mood. When I bought my 1976 Victa the tiny stamped-steel bracket that holds the speed control cable to the governor base was missing, and rather than go buy one from my local mower shop I designed a better one and milled it out of a solid block of steel.
