HSS drill: The top angle is generally 118 degrees, sometimes greater than 130 degrees; the blade is sharp; the requirements for precision (edge height difference, symmetry, 

circumferential runout) are relatively low. There are many ways to repair the chisel edge.

HM drill: The top angle is generally 140 degrees; straight groove drills are often 130 degrees, and three-edge drills are generally 150 degrees. The blade and tip (on the edge) 

are not sharp, often blunted, or called chamfered edges and chamfers; high precision requirements. The chisel edge is often repaired into an S-shape to facilitate chip 

breaking.