If ‘D’ is hole diameter, then general value for a compulsory approach for through hole can be taken as

Drilling is a cutting process that uses a drill bit to create a hole with a circular cross-section in solid materials. The drill bit is usually a rotary cutting tool that is pressed against the work-piece and rotated at high speeds.

Some common types of drilling methods are: Percussion drilling, Auger drilling, Rotary drilling, Jetted drilling, Downhole drilling.