Things You'll Need
10/3 SJ-cord (length determined by you)
1 Male cord plug cap
1 Female cord plug cap
Never use an extension cord as a permanent source of electric in your home. They should only be used for temporary purposes.
How to Make Your Own Extension Cord. Are you tired of having to connect multiple extension cords when performing a job that requires electricity--and there is no outlet nearby? Not only can that get frustrating, but it can be dangerous as well. One way you can solve that issue is to simply make your own custom extension cord. Not only will it serve your purpose better, but it will actually be higher quality than one you can purchase at the hardware store. Here is how to make your own extension cord.
Determine how long of an extension cord you will be needing. If you have a location where you typically perform your work, just measure the length and add a few feet for slack. Typically, the extension cord shouldn't be longer than 24 feet.
Head to the hardware store and purchase the 10/3 SJ-cord and the two plug caps. The 10/3 SJ-cord is a thick, black cord that houses a black, white and green set of wires. It typically costs around $1.50 per foot.
When you return home, take one end of the 10/3 SJ-cord and make a small slice in it with your knife. Take the split ends and pull the outer sheath apart to reveal the individual wires inside. Expose about an inch and a half of the inside wires.
Carefully cut away the excess outer sheath and the strips of paper insulation that are wrapped around the interior wires. Be very careful not to nick any of the wires.
Use your screwdriver and loosen the two screws holding the female plug cap closed. Then, pry the female plug cap open to reveal the wire terminals. You should notice a green terminal, a silver terminal and a copper terminal. Use the screwdriver to loosen each screw on the terminals.
Next, use the wire strippers to strip about half an inch of insulation from each of the exposed wires in the SJ-cord.
Take the green wire and tightly twist the exposed copper wire so that no strands are standing out. Then slip the green wire into the green terminal and tighten the screw down to secure it.
Take the white wire and twist it in the same fashion and secure it under the silver terminal. The black wire gets secured under the copper terminal.
Double-check each wire for any strands that may have escaped. If you notice any, loosen the terminal, retwist the wire and resecure it. Once you are sure there are no stray strands, close the female plug cap and tighten the two screws to complete the plug. The cap should close securely over the black sheath of the SJ-cord. If the individual wires are exposed outside of the cord cap, then disassemble and shorten the wires. The cord cap should close OVER the black outer sheath.
Carefully follow Steps 3 through 9 with the other end of the SJ-cord and the male plug cap. Once you are finished, plug the male end into a powered outlet and test the female end with a voltage tester. If the tester reads 120 volts, then you are good to go!