Electrical Box Punch Out Sizes

Notes to the table above.

Electrical box punch out sizes.

The outlet addition methods we show here are based on the most common wiring 14 gauge wire on a 15 amp circuit and an 18 cu in. The 3 4 inch 1 9 cm trade size is a 1 1 8 inch 2 9 cm opening. Electrical trade sizes and plumbing trade sizes are equal and are based on pipe sizes. It houses a single electrical switch or outlet and comes in metal or nonmetallic units.

The shape of an electrical box can help you identify its purpose. Box typical inside dimensions are about 2 in. A pilot hole is drilled into the box as needed then a draw bolt and die are inserted into the hole and a punch is threaded onto the draw bolt. A screw type or manual knockout punch is tightened with a wrench to knock out the hole.

Temco th0390 manual knockout punch driver kit set for inch to 2 inch electrical conduit hole sizes 1 2 2 conduit size 4 7 out of 5 stars 56 84 95 84. Mophorn 10 ton 1 2 to 2 hydraulic knockout punch driver tool kit electrical conduit hole cutter set ko tool kit with 6 dies hole complete tool knockout punches by mophorn 71 99 71. If you punch out too big of a hole you can use reducing washers. First knockout punched inward for removal.

To determine the actual opening for this size you need to add 3 8ths of an inch which is 7 8ths of an inch opening. First determine the size of the missing knockout hole and subtract 3 8 to figure out what size knockout plug you ll need. Bx cutters after cutting out some concentric knockouts. A standard rectangular shape is the most common electrical box.

Different electrical box sizes fit varying installation needs. If you punch out the wrong hole you can fill it with a knockout seal. An example is 1 2 inch 1 3 cm trade size. The draw bolt is turned by a wrench to pull the punch through the metal making the hole.

In the electrical panel above the inner 3 4 knockout was the easiest to punch out first. Codes also limit the number of wires that can enter an electrical box or electrical receptacle depending on the inside volume of the box and the gauge of the wires.