Reaming
Spot facing
Counter boring
Counter sinking
.
Reduce chattering
Remove more metals
Increase the efficiency
Increase the life of the tool
Prevent rough holes
Prevent over size holes
Prevent unequal angle of cutting edges
Prevent friction of drill behind the cutting edges
75 Degree
80 Degree
90 Degree
120 Degree
Drill held not correctly
Work is not rigidly he
Clearance angle is incorrect
Flutes are clogged with chips