A knockout punch is a set of hardened punches and dies pulled together by a threaded draw stud, turned with a wrench, ratchet or hydraulic driver, to shear a clean hole in an enclosure for a conduit connector. Sizes are marked by conduit trade size rather than actual diameter, so the half-inch punch cuts the 7/8 inch hole a half-inch fitting needs. A pilot hole for the draw stud is drilled first, usually with a step bit.
Bring the hydraulic knockout punch up, we need four two-inch holes in the top of that switchboard.
Plenty of crews call the whole kit the Greenlee, after the brand that dominates it.
Also heard as
- KO punch
- KO set
- Greenlee
Related terms
KO
Knockout: a partly punched disc in a box or panel that is removed to make a hole for a conduit or cable fitting.
Slug
Metal disc knocked or punched out of a box or panel, which ends up underfoot and in the bottom of every panel.
Unibit
Stepped cone drill bit that cuts several hole sizes in sheet metal boxes and panels, named for its brand.