Miller Feed Rolls FAQs
Answers to common questions about choosing, fitting and looking after MIG wire feed (drive) rolls.
Which groove type do I need: V, U or knurled?
The groove is chosen to suit the wire. A smooth V-groove is normally used for hard solid wires such as mild and stainless steel. Knurled (toothed) rolls grip flux-cored and metal-cored wires, which are a thin tube filled with flux or metal powder, so they are softer than solid wire. A smooth, rounded U-groove is used for soft wires such as aluminium, which deform easily.
The wrong type either slips or marks and shaves the wire. Check what your machine's manual recommends for the wire you plan to use, as a few designs differ from the usual pattern.
How tight should the feed roll pressure be?
Use the lowest pressure that feeds the wire steadily. Too little pressure and the rolls slip. Too much pressure flattens or deforms the wire, wears the rolls and liner faster and can make the wire tangle at the rolls if something downstream holds it up. Tightening the pressure to cure a feed problem is a common mistake.
Start with the maker's guidance for your wire type, then adjust a little at a time until the wire feeds smoothly. Soft wires such as aluminium and some flux-cored wires need particular care.
Can I use steel feed rolls to weld aluminium wire?
Usually not. Aluminium wire is soft, and the choice of drive roll is a major cause of feeding problems with it. Rolls with a rough or sharp-edged groove, or rolls that are misaligned, shave fine particles off the wire, and these build up in the groove and liner.
For aluminium, use rolls made for soft wire, normally with a smooth U-shaped groove, set to the lowest pressure that feeds the wire. Many users also fit a liner made for aluminium. Follow the machine and wire makers' instructions.
My wire feeds badly or tangles at the rolls. What should I check?
Do not assume the rolls are the cause. Check the groove type and size against the wire, then the roll pressure. Then look downstream: a worn or blocked contact tip, or a dirty, kinked, wrong-size or wrongly trimmed liner, stops the wire while the rolls keep pushing, and the wire piles up at the rolls.
The liner should be a little larger than the wire and cut to the correct length. Replace it when buildup causes erratic feeding. Also check that the rolls line up with the inlet guide.