Tap drill size = Major dia ? (2 x depth)

Tap drill size = Major dia + (2 x depth)

Tap drill size = Major dia ? (2 + depth)

Tap drill size = Major dia + (2 + depth)

Too fast feed rate

Too slow feed rate

More cutting speed

Too slow spindle speed

Rule

Centre head

Square head

Protractor head

Provide flatness

Prevent distortion

Provide squareness

Support the machined surface

Up to 1.2 %

Up to 1.7 %

Up to 1.9 %

Up to 2.1 %