As shown in the table below, it is possible to select the most suitable cutting edge geometry for different applications. If the most suitable cutting edge geometry is selected then higher machining efficiency and higher hole accuracy can be obtained.
Cutting Edge Shapes
Grinding name
Shape
Features and effect
Application
Conical
The flank is conical and the clearance angle increases toward the centre of the drill.
General Use
Flat
The flank is flat.
Easy grinding.
Mainly for small diameter drills.
Three flank angles
As there is no chisel edge, the results are high centripetal force and small hole oversize.
Requires a special grinding machine.
Surface grinding of three sides.
For drilling operations that require high hole accuracy and positioning accuracy.
Spiral point
To increase the clearance angle near the centre of the drill, conical grinding combined with irregular helix.
S type chisel edge with high centripetal force and machining accuracy.
For drilling that requires high accuracy.
Radial lip
The cutting edge is ground radial with the aim of dispersing load.
High machining accuracy and finished surface roughness.
For through holes, small burrs on the base.
Requires a special grinding machine.
Cast Iron, Aluminium Alloy
For cast iron plates.
Steel
Centre Point drill
This geometry has two-stage point angle for better concentricity and a reduction in shock when exiting the workpiece.