Advanced Drilling

Point angle and cutting edge

The point angle is an important factor that influences chip disposal, cutting resistance, burr formation and the surface roughness of a drilled hole. High-speed steel twist drills, usually have a point angle of 118° to achieve a combination of both long tool life and stable drilling. Additionally the flute geometry is designed to have a straight cutting edge with the optimal 118° point angle.


The image shows the effects on the cutting edge when changing the point angle during regrinding. When changing the point angle to 140° the actual cutting edge becomes concave, this improves the chip breaking properties. When the point angle is changed to 90° the cutting edge becomes convex, this will assist in burr prevention. However, changing the point angle of a high-speed steel drill to the above may reduce the cutting edge strength. This can make the cutting edge prone to chipping and fracturing.