i bought a welder that needs 3 phase 1 or 2 legs it says.how do i go about converting the 220 thats already there?

mt short, May 2009

You need a single to 3 phase convertor. That can be either a solid state device that does it using electronics or a rotating machine - i.e. a single phase motor driving a 3 phase generator.
You really need to check how many kVA your 3 phase welder requires. If its 3 phase its likely to be a big unit. Your domestic (assumed) single phase supply can only deliver a limited kVA and if the new welder needs more than that, converting your single phase to 3 phase will be a waste of time anyway and you will need to apply for a proper 3 phase supply.

J, May 2009