How to mig weld part 6: Drive rolls / feed rolls

Your feed roller or drive rolls however you like to call them are there to push the wire through the liner and gun cable all the way up to where you need to weld.

They are little wheels with grooves in them. Some machines will have the one feed roller and an idle bearing on top. Other machines will have two drive rolls, and other will have four drive rolls. The simple fact is the more feed rollers there are means more surface area, which means more traction.

You need to make sure that you use the correct size feed roller for the wire being used. So if you are running a 0.8mm (.030") wire you need to use feed rollers that are stamped on the side with the same numbers. Usually there are two places that you can put the wire in. The deal is that one side is for a smaller wire and the other side is for a lager wire. This way all you have to do is turn the feed rollers around when you want to run bigger or smaller diameter welding wires.

There are also different types of feed rollers that you can get. They are designed for different to be used with different welding wires.

Standard groove rollers

Called V groove rollers these are what you need to use when you are welding with a solid mig wire. The slot that is in the drive roller has been machined on a lathe and has a small V shape cut made in it.

Knurled drive rolls

When you are welding aluminum though, because it is much softer a standard V roller will not work that well. If at all, I've never tried. Mig welding aluminium is renowned for having wire feeding issues. The biggest issue is that you can get the wire to feed up the gun smoothly. This is why you need to use U groove rollers. These ones have a machined grove that is in the shape of the letter U. By having this nice smooth curve at the bottom it will allow the wire to have more surface area contact. This extra contact means more grip and traction. Perfect for feeding soft bendy aluminum wires.

Aluminum feed rollers

Knurled drive rolls are used with flux cored welding wire. They have a series of slits machined in the grove of the roller so that they sort of have rough, teeth like grip. Gasless mig wire and flux cored wires are also very soft, therefore you need to use this type of drive roll.

Note: You really should use a U groove drive roll for flux cored wires as the rough edges of the feed roller will slowly eat away the wire and send bits it down the liner. This over time will cause it to block up and cause wire feeding issues. In Asia where there is an awful lot of welding done they don't like knurled feed rollers for this reason.

How to mig weld. Part 7. Gas regulator.