4mm HSS Black Stub Drill

About this item:

• 4mm 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.