What's the best way to make or buy one of these? I was thinking something like a 15' one for my plasma cutter.
Depending the max amp draw of whatever you want to make a cord for its fairly simple. Made a 50 footer for my mig welder (Max draw 50 amps) and a 15 footer for my compressor. Both are 220 volt...The compressor is single phase so I only needed a 2 wire cord.(It only pulls 25 amps on statup) The cable I used was 10 AWG 3 wire loose strand Outdoor...Has a rubber sheath.( For the welder) I used (12 AWG outdoor for the compressor) That and the proper plugs for your set up and Bobs your uncle...Good luck Mo!!!
it's very simple to make them..and cheaper just make sure you get the proper rated wire and 15' or whichever length, don't forget about your voltage drop that will occur, going a little larger will reduce or stop that, less resistance. forgot to answer your question, best way to make it is by going to your closest electrical wholesaler..or maybe home depot depending on what price. and get them to cut you a length off of a spool, that stuff they should have no problem cutting, they even may have thicker insulation if there will be heavier things on it or hitting it..just depends what you are looking for. from there you just buy the appropriate plug ends and they are super simple to put together.
Go to the electronics department at your local Lowe's, Home Depot, Ace Hardware, etc. They will cut you the proper wire to length and hand you the proper plugs. Ask nice and they will explain how to assemble. It is fairly easy, you just cut wire, bare ends, and tighten screws.