Forage des roches — Matériels pour forage percutant de longs trous — Équipements à filetage à butée inverse 1 1/2 à 2 1/2 in (38 à 64 mm)

Specifies the basic dimensions for equipment. Gives a list of components; tabulates together with figures: size of drill-steel in bar form; lengths of extension rods; coupling sleeves; bit diameters (four-wing bits); reverse-buttress threads; hollow hexagonal bars for extension rods.