The rule that works
The electrode diameter should be close to the workpiece thickness, without exceeding it. Amperage comes from the diameter, not the thickness: roughly 35 to 45 amps per millimetre of electrode.
| Electrode | Inches | Amperage | Thickness |
|---|---|---|---|
| Ø 1.6 mm | 1/16" | 40-70 A | 0.8-2 mm |
| Ø 2.0 mm | 5/64" | 50-90 A | 1.5-3 mm |
| Ø 2.5 mm | 3/32" | 70-110 A | 2-5 mm |
| Ø 3.2 mm | 1/8" | 90-150 A | 3-8 mm |
| Ø 4.0 mm | 5/32" | 130-200 A | 6-14 mm |
| Ø 5.0 mm | 3/16" | 180-270 A | 10-25 mm |
Start mid-range and adjust. Our welding calculator also applies the correction for material and position.
Correct for position
Vertical and overhead call for 10 to 15% less amperage. The puddle is heavy and will drop on you if you run too hot.
Which electrode for which job
- E6013: general use, easy strike, tidy bead. The one you want for sheet and everyday work.
- E6011: real penetration, forgives paint, rust and damp. The site and dirty-repair rod.
- E7018: low hydrogen, for structure and parts that will take load. Needs a clean joint and a dry rod.
- E308L / E316L: stainless. Lower the amperage and avoid overheating.
- ENi-CL: cast iron. Short beads, peen between passes and let it cool slowly.
Read the bead and correct
- Heavy spatter and the rod sticks: not enough amperage.
- Burn-through and a sunken bead: too much amperage.
- Tall narrow bead with poor fusion: travelling too fast or running too cold.
- Wide flat bead with the rod burning off on its own: too hot or too slow.
The detail nobody mentions
Keep your electrodes dry. An E7018 left overnight in a damp shop welds badly and brings porosity, no matter how well you set the machine. Use a rod oven or, at the very least, a closed box with the packet properly sealed.
