GRAFF drill bit 20,5 mm with a grooved shank is designed for drilling alloyed and unalloyed steels with a tensile strength of up to 800 N/mm2, metal ceramics, cast iron and non-ferrous metals. They are made of high-quality rapid steel HSS 4241 with finishing by steam oxidation, which increases durability and service life. Angle of sharpening at the apex is 118 degrees.
The peculiarity of these drills is that they have a grooved shank, which makes it possible to use drills of bigger diameters in regular drills with a small holder-adapter.
Parameters of a GRAFF drill bit 13 mm with a grooved shank: D = 20,5 mm – drill bit diameter, d = 13 mm – shank diameter, L1 = 140 mm length of the working part, L2 = 205 mm – total length.