Description

Bordo HSS Black Stub Drill Bit - 2021

HSS Black Stub Drill.
Stub drills (screw machine twist drills) have a shorter overall length than Twist drills for maximum rigidity and longer tool life.
135° Split Point (crankshaft point).
Split point is self centering and the short distance from the drill axis to the outer corners results in faster penetration, reducing the need for end thrust.
They are designed primarily for machining operations in lathes (screw machines) but can also be used in manual hand held drills.
Bordo Stub Drills have two helical flutes with 30 degrees of helix angle. This provides fast chip ejection and very stable drilling operation.
Black Finish Stub Drills (also called blue finish) achieve their distinctive colour by steam tempering, a thermal process resulting in a porous tool coating.
Black finish tools are generally recommended for ferrous applications where the oxide layer aids chip flow and heat dissipation.

About 135° Split Point (crankshaft point)

The split point is self centering and the short distance from the drill axis to the outer corners results in faster penetration, reducing the need for end thrust.
The 135° point should be used to cut harder steel materials especially in deep hole applications. In these situations, it will produce thicker chips minimising work hardening of the cavity.
Faster penetration reduces abrasion and friction along the cutting edges.