Solid wire is fed by a smooth V-groove roller squeezing it. Flux-cored wire is a folded metal tube filled with powder, and the same pressure flattens it — after which it jams in the liner or feeds erratically.
A knurled roller grips the surface instead, so the tension can be set lighter for the same feeding force.
The questions welders ask
Can I run solid wire on a knurled roller?
It works and it shaves the wire, leaving copper dust that ends up in the liner and the tip. Machines usually ship with a reversible roller carrying a V-groove on one side and a knurl on the other, and turning it over takes a minute.
Last reviewed 2026-08-14