This International Standard specifies the characteristics of half-length centre grooved pins made of steel or austenitic stainless steel which have three equally spaced grooves impressed longitudinally on their exterior surface, with nominal diameter, d1, from 1,5 mm to 25 mm inclusive. The displaced material to each side of the grooves forming an expanded diameter, d2, which is larger than the nominal diameter d1 will cause a non-positive locking fit when these grooved pins are forced into a drilled hole equal to the nominal diameter d1 (see clause 4).