Knockout punch

[2] First a pilot hole is drilled slightly larger than the screw of the knockout punch.

A manual knockout punch can handle holes from 0.5 to 1.25 in (13 to 32 mm).

This type of system has a mechanical advantage of approximately 220:1 and can punch holes up to 3 in (76 mm) in diameter in 10 gauge mild steel.

It is a two piece system where the dies are attached to the ram which is connected to the hydraulic unit via a flexible hose.

Other shapes include square, hexagonal, and special shapes for thing such as holes with key tabs and D-sub connectors[7] Special shapes often use bolts that are square or keyed and a separate nut on the punch end to ensure alignment of the punch and die.