Electrical Box Punch Out Sizes

First determine the size of the missing knockout hole and subtract 3 8 to figure out what size knockout plug you ll need.

Electrical box punch out sizes. The national electrical code article 314 contains complete details and tables of electrical box sizes in dimensions and cubic inches and should be consulted for complete accuracy because the actual size of the box required in cubic inches depends on the number of wires that will be within that enclosure. The shape of an electrical box can help you identify its purpose. Bx cutters after cutting out some concentric knockouts. In the electrical panel above the inner 3 4 knockout was the easiest to punch out first.

Notes to the table above. 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. The 3 4 inch 1 9 cm trade size is a 1 1 8 inch 2 9 cm opening. Standard piece makertm punch and conduit size actual punched hole diameter in 1560.

If you punch out too big of a hole you can use reducing washers. First knockout punched inward for removal. Electrical trade sizes and plumbing trade sizes are equal and are based on pipe sizes. Box typical inside dimensions are about 2 in.

A screw type or manual knockout punch is tightened with a wrench to knock out the hole. 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.

A standard rectangular shape is the most common electrical box. The draw bolt is turned by a wrench to pull the punch through the metal making the hole. 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. For example if you have a 7 8 hole you ll need a 1 2 knockout plug.

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. It houses a single electrical switch or outlet and comes in metal or nonmetallic units.