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Heavy steel angle iron is within reach of many shop plasma cutters, but thickness, duty cycle and the cut’s fit-up matter more than a headline amperage figure. For ordinary structural angle up to about 1/2 inch thick, a quality 40- to 50-amp machine is usually the practical range. For frequent cuts in 5/8-inch or thicker stock, look at a 60- to 80-amp cutter—and check its rated cut capacity, not just its maximum severance claim.
What heavy angle iron demands
Angle iron has two legs, and cuts often cross a corner or require separating both legs. That puts more demand on the cutter than a short, straight cut through a flat plate. Rust, mill scale, paint and a poor ground connection can also make an otherwise capable machine sputter or lose its arc. Clean a small patch to bare metal for the ground clamp, and remove coatings near the cut; painted or galvanized material can produce hazardous fumes.
Manufacturers commonly list a clean-cut thickness and a maximum severance thickness. The first is the useful buying figure: it describes a cut made at a workable speed and quality. Severance means the cutter can part the metal, often slowly, with a rough edge. If you regularly cut 1/2-inch angle, don’t buy a machine whose clean-cut rating is only 1/2 inch and expect easy production. Leave headroom.
Which cutter category fits?
| Category | Best fit for angle iron | Trade-off |
|---|---|---|
| 30–40 amp, 120V or dual-voltage | Occasional cuts in lighter angle, roughly 1/4 inch or less | Portable and often inexpensive, but slower and less comfortable on thick legs or corners |
| 40–50 amp, 240V or dual-voltage | Regular shop work through roughly 3/8–1/2 inch, depending on the machine | Good balance of capacity and cost; needs a suitable 240V circuit for full output |
| 60–80 amp, 240V | Frequent heavy cuts, thicker stock, or faster work | Higher cost, larger power demand and often more air consumption |
These are screening ranges, not guarantees: torch design, air pressure, travel speed and the maker’s test method affect results. Verify the machine’s rated cut at the thickness you actually use.
Best picks by job type
For occasional repairs and lighter angle: A compact 30- to 40-amp cutter can be the sensible choice when most work is under 1/4 inch and cuts are short. It may run from 120V, though output is typically limited on that supply. A dual-voltage unit offers flexibility, but don’t assume a standard household outlet will deliver full rated power. Check the required breaker and plug. Browse dual-voltage 40-amp plasma cutters if portability matters more than sustained heavy cutting.
For a general-purpose fabrication shop: A 40- to 50-amp machine on 240V is the best starting point for many users cutting angle, plate and brackets. Look for a published clean-cut rating above your normal thickness, a decent duty cycle and consumables that are easy to source. This category usually avoids paying for capacity you rarely use while cutting substantially more comfortably than small 120V machines. Compare 50-amp 240V plasma cutters against your shop’s circuit and air setup.
For repeated cuts in thick stock: Choose 60 amps or more when production speed and a cleaner edge on heavy material matter. A larger machine is not automatically better if the compressor cannot keep up or the circuit is undersized. Check the manual for input amperage, recommended breaker, air pressure, airflow and duty cycle before buying. A 60-amp 240V plasma cutter can be a better fit than repeatedly pushing a small unit at its limit.
Air supply and duty cycle are not optional details
Most air plasma cutters need clean, dry compressed air. Match the compressor to the cutter’s stated cubic feet per minute (CFM) at the specified pressure, not its tank size alone. A small tank may support a short cut but run out during a long one; a compressor that cannot maintain flow causes arc instability, excess dross and shortened consumable life. Add a suitable water separator or filter, drain the tank, and keep the hose and fittings large enough to avoid starving the machine.
Duty cycle tells you how long a cutter can run within a 10-minute period at a stated output. For example, a 40% duty cycle means about four minutes of arc time followed by six minutes of cooling at that rating. Frequent starts, long cuts and high amperage build heat quickly. If you cut several long pieces in a row, prioritize a stronger duty cycle over a flashy maximum-thickness number.
Cutting angle iron cleanly and safely
Clamp the work securely and plan the cut so the torch can travel without the tip striking the opposite leg. For a corner cut, approach steadily and keep the torch square to the face; slowing dramatically at the junction can leave a heavy dross bead, while rushing can leave an incomplete cut. Use the manufacturer’s recommended standoff or drag shield, and replace a worn electrode or nozzle when the arc wanders or the kerf gets wider. Don’t compensate for worn consumables by turning up air pressure beyond specification.
Use a welding helmet or plasma-rated face protection, safety glasses, gloves, hearing protection and nonflammable clothing. Plasma cutting throws hot metal and sparks; clear combustibles well beyond the immediate work area, and never cut a closed or contaminated container. If the job is a few cuts in thick angle and you lack 240V power or adequate compressed air, paying a shop to cut it may be cheaper than buying an oversized setup.