I have a lincoln 225 welder and when you plug a grinder or band saw into it and you lay the band saw on a metal table beside the welder after your done using it it arcs on the table, and a grinder does the same thing.

The first thing with this situation is be vary careful this can KILL,
insure that the ground contact to your welder is of good quality, you might have a voltage induced in the metal frame of your welder by the large transformer(inductor) used to modify the voltage/current to a value you can weld with, with a good ground this will not happen, if the ground contact is poor, and you repair the contact, plug it in and it trips the barker, your welder is faulty by way of the primary coil in the inductor contacting the metal body of the welder, this is not worth repairing, also look for any wires that may have worn off its insulation and are contacting the mettle frame of the welder, a good ground will save your life, insure that all your power tools that have a 3 wire cord have a ground contact. good luck and always be safe