Twist Drill of 8. 5 diameter in mm X Length aas IS: 5101- 1991 & 5099- 1983, HSS Twist Drill parallel Shank L. H. generally confirming to IS: 5101- 1969 & 5099- 1983 size 8. 00 mm di, HSS Drill 4 mm with Flute length 15 mm to 20 mm ( after grinding ) point angle 170 degree & spiral ang