Výroba kruhových otvorů

This thesis deals with the problem of machining circular holes. The subject of the study is to trace down changes in the condition of cutting tool parts - in particular, twist drills from dif-ferent materials and of various geometries depending on the number of drilled holes. Ma-chined material was a constructional steel sheet with a thickness of 25 mm. Drills were from four types of material - high speed steel, high speed steel with titanium nitride coating, high speed steel 5% cobalt and steel drill with brazed cutting inserts made of sintered carbide. Measured and compared parameters were: changes in the electric power input, hole diameter changes and changes in surface roughness