Holes of machine
No machine can make it without holes. To connect the parts, you need a variety of screw holes, pin holes or rivet holes. In order to fix the transmission parts, you need a variety of mounting holes. Process holes, weight reduction holes, etc.).  The operation of machining holes to achieve the required holes is called hole machining.
The inner hole surface is one of the important surfaces that make up mechanical parts. In mechanical parts, parts with holes generally account for 50% to 80% of the total number of parts. There are various types of holes, including cylindrical holes, conical holes, threaded holes, and shaped holes.