Draper expert 41mm cobalt twist drill for helicoil thread repair kits draper expert 76093 expert quality a selection of metric sized high speed steel straight shank drills with 5 cobalt for specifically drilling out damaged threads prior to insertion of a helicoil174 insert the addition of cobalt to hss adds strength and wear resistance for longer life for use with unc and unf helicoil174 thread repair kits display packedmanufactured to din338 and iso2351 specifications draper