Dad has just phoned, and the welding rods are just a smidge over 3/32" he said its about 4 thousands of an inch too big, which is 0.00635mm i believe, so this could easily be sanded down with some emery (so) paper. If you want one let me know and i'll send one over to you when i'm back next week,

JB

(ps it is def. mild steel)