Oversize taps cut a slightly enlarged pitch diameter (specified as a plus tolerance, e.g. +0.05/+0.1 mm), to compensate for thread shrinkage after tapping, to keep fit accuracy after plating/painting/heat-treatment, or to repair slightly undersized threaded holes. Common where a looser fit or coating allowance is needed. Mainly HSS. Specify the oversize amount (tolerance class) and thread spec so the fit class with the mating bolt is correct; too much oversize reduces thread contact and strength.