You can find the opening sizes for heat sets on McMaster Carr's site. This is from memory, however I utilize a 5.2mm opening with a 4mm profundity for a standard M3 heat set embed, and a 7.3mm opening with a 5mm profundity for a M5 I think. The more M3 and M5 ones require a smaller opening with more profundity.

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Tasmania - M3 Heat Insert

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