BenchWeld's welding references are built for the moment the arc stops cooperating — wire that won't feed, a fault light you can't read, a bead full of porosity. Every guide is tied to a specific machine and names the exact consumable the fix needs, because the part that fits a Lincoln Magnum 100L gun is not the part that fits a Miller M-100 or a Hobart H-series.
When a MIG welder won't feed wire, the instinct is to suspect the machine — but the cause is almost always mechanical, in the path the wire travels from the spool to the contact tip. Work it in order: drive-roll tension first, then the groove size and type, then the liner, then the tip. Set tension by backing it off and tightening only to about a half-turn past where the wire stops slipping; over-tightening shaves the wire and packs the liner with debris, which causes the very birdnesting people are trying to stop. Get that sequence right and you've solved the large majority of ‘won't feed’ calls without ever opening the case.
Three things have to agree: the drive-roll groove (a smooth V for solid steel, a U for soft aluminum, a knurled V for flux-cored wire), the contact-tip bore (sized to the wire diameter), and the liner (sized to the wire and cut to the gun’s length). Get any one wrong and the wire feeds badly. This is also why our guides are per-machine rather than one generic article: the tip, liner, and drive roll that fit a Lincoln Weld-Pak’s Magnum 100L gun differ from a Hobart Handler’s H-series, a Millermatic’s M-100, or an ESAB Rebel’s Tweco Fusion — and ordering the wrong one is the most common way a ‘simple’ fix stalls.
Modern inverter machines tell you what’s wrong: a Millermatic 211 blinks a status code (three flashes for a wire-drive fault, two for a thermal trip), and an ESAB Rebel surfaces feed-roll and brake remedies in its manual. Older transformer machines stay quiet — a Hobart Handler 140 that quits mid-weld is usually a thermal cutout protecting the transformer, not a dead feeder, and it resets itself after a cool-down. Knowing your machine’s particular tells saves you from tearing down a gun that was never the problem.