It seems really easy to find the opposite (how to plug a 4 prong plug into a 3 hole outlet) but I actually need the reverse (I need to plug a 3 prong plug into a 4 hole outlet) and not sure if it even exists.
...which includes a 240, 3 prong plug. It's the kind that looks like your standard plug (two parallel prongs and a ground). It's not the kind dryers use where you have 3 angled prongs.
On the wall-side, I have a 40amp, 4-wire outlet (2 hot, neutral, ground).
Is there a way to use this welder with this outlet? If so, is there an off-the-shelf adapter for this? If not, could I wire up my own using a 4 prong plug wired into a box with a 3 prong outlet. If I can do the latter, what's the proper way to do that?