The cheap way to make one is to buy the two ends that you need and then buy a 25 foot 10/3 110 volt extension cord. (they are cheaper than the wire is) and cut the ends off of it and put yours on. Don't make it any longer than 25 feet or it will get warm (HOT) in use.
After searching the local box stores for any kind of heavy duty wiring, Paul's idea is still the best one. I have a 6 foot cord that my grandpa made for his stick welder, but I'd have to wire in a new receptacle (I think he used an old dryer cord) and it still wouldn't be long enough. These home improvment stores are crap. Unless you're building a deck, they're pretty much so worthless. Between Lowes and Tractor supply, I can normally cobble something together. I miss my old hardware store out in the country...
That is why I stay away from the new chain stores and support the old hardware store. They have been around for the 57 years that I have and more. I can get a replacement element for a stove built in the 40's and plumbing repair kits for the new ceramic seal faucet I bought last year from them. They sell springs, cable, rope and chain by the foot and screws and nails by the pound. If it is hardware related and they don't have it, I don't need it!
i made mine outta 10/3 and its 50 ft. no heat problems. runnin a 180 mig all day on it. use twistlocks, youll appreciate them. cost me about 75 clams total in the end.
Wages, you are only running about 20 amps through that extension cord... My mig uses a bit more than that. You could actually use 10 gauge wire to 75 feet using 20 amps - according to THE BOOK.
