DescriptionGRAFF drill bits, Set of 10 are made of HSS steel by rolling (screw-rolling) method with ground edge according to DIN338 standard. Drill bits have a cylindrical shank for a drill. Angle at the apex of 135 degrees and cross undercutting provide excellent drilling of metal without pre-drilling. Drill bits are used for drilling bores in alloyed and unalloyed steels, malleable and gray cast iron.  Diameter, mm  Totallength, mm  Workingpart, mm   Recommended rotationsper minute, rpm      1     34     12     5740     2     49     24     4780     3     61     33     3820     4     75     43     2870     5     86     52     1910     6     93     57     1720     7     109     69     1530     8     117     75     1340     9     125     81     1150     10     133     87     960