Welder extension cord

[spider]

Ok folks this is a bit confusing but bare with me.

I recently purchased a Lincoln Mig Pak 15 on sale. it's a 220V welder.
I figured that my Dryer plug would be the same type of plug but I was incorrect.
The dryer outlet has 4 prongs, this welder has three, so I spoke to a few electricians and they said I could make an extension cord but a conversion mod would have to be done to make a 3 prong work with a 4 prong.
So here's a drawing of wha I plan to make. So all you master electricians out there let me know what you think, if it's safe or not. Thanks.

[kbaillie]

Yes that would work fine, You really could drop the box size down to 4x4 shallow. I would make sure you pigtail the ground though. If you want a better cordwithout the box, go to a electrical supplier and buy a dryer "cord end",just the end not with cable which you can take apart and wire up without the neutral. The end will cost you more money but then you wont have the jb in the cord.

[spider]

~I would make sure you pigtail the ground though.
~The end will cost you more money but then you wont have the jb in the cord.

What do you mean by pigtail the ground? I was just going to screw the ground wires to the box.

The dryer plug end... thought about that and almost went that route but 65 bucks for the end compared to the cord and plug that goes for 10 bucks.

Thank for the info kbaillie, I appreciate it.
Regards,
Plasma

[spider]

Ok it's all complete, thanks to all who helped out.
Got some pics of the completed cord, sorry for the crappy images , they were taken with my camera phone.

Welder recepticle wired up


Welder recepticle complete


Jbox half way complete


neutral wire from dryer cable capped off


Cord complete

[Sberry]

That will work.

[Sandy]

What do you mean by pigtail the ground? I was just going to screw the ground wires to the box.

What is meant by that is to make sure that the bare ground is also spliced through in some sort of method close to code. Generally that would be the crimped splicing ring/sleeve or wire nut. Coarse threaded screws on copper aren't famous for staying tight.

[Sberry]

I think what he meant was to wirenut the grounds together and add a 3rd one in to ground the box.