Choosing The Proper Length Drill:
Always select the shortest drill possible for an application. The increased rigidity will dramatically enhance
the number of holes per grind, as well as hole concentricity and location.
Drills over 1" diameter have reduced shanks:
- 1 1/16" to 1 1/4" sizes have 1" shank
- 11 5/16" to 1 1/2" have 1 1/4" shank
- 11 9/16" to 2" have 1 1/2" shank
Choosing Between 118° And 135° Drill Points:
118° point angles are used primarily in softer materials such as mild steels and cast irons.
135° split points should be used to cut harder steel materials and especially in deep holes over 4 times the
drill diameter. With a 135° drill point, cutting harder materials will produce thicker chips, minimizing
work hardening of the cavity. The length of the lips on a 135° point drill, measured from the axis to the
outer corners, is relativity short. This enables quicker penetration into the workpiece and reduces thrust
and abrasion along the cutting edges.