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Before You Cut

Expanded metal cuts easily with a plasma torch, but its open pattern creates a different problem from cutting solid plate: the arc repeatedly crosses from metal to air. That can interrupt the cut, widen the kerf, and leave small uncut bridges at the ends of each diamond. A steady hand, clean work support, and the right consumables matter more than simply turning up the amperage.

Identify the material first. Mild steel is the simplest case. Stainless steel and aluminum also cut with plasma, but they need clean, dry compressed air or the gas specified by the cutter manufacturer. Painted, oily, galvanized, or zinc-coated expanded metal can produce hazardous fumes. Remove coatings where practical, improve ventilation, and use suitable respiratory protection based on the coating and local requirements. Never cut indoors without controlling smoke and sparks.

Tools and Safety Equipment

Use a plasma cutter rated comfortably above the thickness of the expanded metal’s strands. The nominal sheet thickness is not the whole story: expanded metal may have thin ribs but a thicker edge where several strands meet. A machine with a 40-amp cutting rating is usually more versatile than a small 20-amp unit, but the cheaper option is fine for occasional cuts in light-gauge mild steel if it has reliable pilot-arc starting and enough duty cycle.

You will also need a dry air supply, an air filter or water separator, a solid work clamp, and a nonflammable cutting surface. Wear a properly rated plasma-cutting helmet, leather gloves, long sleeves, hearing protection, and leather boots. Plasma arcs emit intense ultraviolet light, and the open mesh can scatter sparks in unexpected directions. Keep flammable materials well beyond the spark range, not just directly below the cut.

For a helmet, an auto-darkening plasma cutting helmet with a shade range that includes the amperage you use is more convenient than a fixed-shade shield. A fixed shield is perfectly serviceable for occasional work if its shade is correct and you can see the layout.

Choose the Setup

Check the manual for input air pressure, flow, and maximum clean-cut thickness. Many compact machines operate around 60–70 psi, but the correct setting is the one printed for your cutter. Excess pressure can make the arc unstable; too little pressure overheats the torch and damages the electrode. A plasma cutter air filter and water separator is inexpensive insurance, especially with a shop compressor that produces condensate.

Mark and Support the Metal

Mark the cut with a paint marker or scribe. A chalk line can disappear under the arc and sparks. Place the expanded metal flat on a steel cutting table or on sacrificial supports that leave an air gap below it. Do not lay it directly on a valuable table if you need to protect the finish or prevent the work from sticking to the grate.

Clamp the sheet so vibration does not make the torch bounce. Keep the ground clamp on clean bare metal, as close to the cut as practical. Expanded metal can have poor electrical contact at its edges, particularly when it is painted or rusty. If the arc starts and stops as you move, stop and improve the ground rather than forcing the torch forward.

Cutting Procedure

Install the correct nozzle, electrode, and shield cap for the amperage and cutting mode. Inspect the consumables before starting. A badly pitted electrode, enlarged nozzle hole, or cracked shield cap will produce a wandering arc and angled cut.

Set the amperage according to the machine’s chart, then start slightly slower than the rated maximum speed. For a hand cut, hold the torch perpendicular to the sheet. If your torch is designed for drag cutting, let the tip lightly contact the material; otherwise maintain the specified standoff, commonly about 1/16 to 1/8 inch. Do not drag a non-drag torch directly on the mesh.

Start at an edge or use a short lead-in outside the finished line. Pull the torch in a smooth motion rather than pushing it. The sparks should exit through the underside. If they spray back toward you, the travel speed may be too fast, the amperage too low, or the torch angle wrong. On expanded metal, pause briefly as the arc crosses each heavy intersection, but do not dwell so long that you enlarge the holes or warp the sheet.

When cutting an interior opening, pierce only where the small starting hole will be hidden or trimmed away. Keep the torch moving as soon as the arc transfers. A high-quality plasma cutter cutting guide can improve circles and repeated shapes, although freehand cutting is often faster for rough utility panels.

Troubleshooting and Finishing

Large bottom-side dross usually means the cut is too slow, the amperage is too low, the air is wet, or the consumables are worn. A narrow, incomplete cut usually points to excessive speed, inadequate amperage, poor grounding, or losing the correct standoff. If the arc goes out in the open spaces, reduce speed slightly and keep the torch centered over the next strand instead of sweeping across empty air.

Let the piece cool before removing it. Knock off light dross with a chisel or wire brush, then use a flap disc only where necessary. Grinding every edge can round the diamond pattern and remove more material than intended. Inspect for sharp points and uncut bridges, particularly at corners and where the cut crossed overlapping strands. Deburr those areas with a file or abrasive pad before handling or welding the piece.

For repeated production work, a larger cutter with a machine torch and a proper cutting table will give more consistent results. For one-off repairs and light fencing or guards, a compact hand torch is usually enough—provided you control the air, ground, speed, and sparks.