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Expanded metal is harder to cut cleanly than a solid sheet because the cutter repeatedly moves from metal to open air. With a plasma cutter, that can make the arc drop out, sputter, or restart across the diamond-shaped openings. A grinder avoids arc problems but creates more heat, noise, and abrasive dust. The best method depends on the mesh size, thickness, and how much edge distortion you can accept.
Why Expanded Metal Challenges an Arc
Expanded metal is slit and stretched from one sheet, leaving raised strands and open spaces. As a plasma torch travels along a strand, it can suddenly reach an opening. The cutting arc then has no conductive workpiece directly below it. Some plasma cutters maintain the pilot arc, but the main cutting arc may extinguish. Others restart slowly enough to leave a notch or oversized gap.
Raised strands create a second problem. The torch may be at the correct height over one part of the mesh and too far away over the next. A handheld plasma cutter is forgiving, but excessive stand-off reduces energy transfer and widens the cut. A drag shield or a small guide wheel can help keep the torch moving at a consistent height.
Clean the material first. Oil, mill scale, paint, and galvanized coatings interfere with electrical contact and produce unpleasant fumes. On galvanized expanded metal, remove the coating several inches around the cut or use strong local extraction and suitable respiratory protection. Never rely on a welding helmet alone for coating fumes.
Choose the Cutting Method
| Method | Best use | Main advantage | Main drawback |
|---|---|---|---|
| Plasma cutter | Medium and heavy expanded metal | Fast, low mechanical force | Arc can drop across openings |
| Angle grinder | Thin mesh, short cuts, rough edges acceptable | Works through open areas without arc loss | Dust, sparks, and slower long cuts |
| Reciprocating saw | Installed material or awkward access | Little electrical setup | Teeth catch and bend fine mesh |
| Air nibbler | Thin sheet and light expanded metal | Minimal heat and clean control | Limited thickness and compressed-air demand |
A plasma cutter is normally the best choice for thicker carbon-steel mesh, especially when you have many cuts to make. For thin expanded metal under roughly 1.5 mm, a grinder with a thin cut-off wheel can be cheaper and more predictable. If you only have one small cut, buying a plasma cutter is not economical; use a grinder, nibbler, or metal-cutting saw instead.
For plasma work, look for a machine with a reliable pilot arc, adjustable amperage, and a drag shield. A plasma cutter with pilot arc is more useful on mesh than a basic contact-start unit because it can cross small gaps without forcing the tip against the work.
Prepare the Workpiece and Ground
Support the expanded metal on a nonflammable table or a pair of steel sawhorses. Do not lay it flat on a solid steel table if the table blocks the openings and causes reflected heat and slag to build up. A slatted cutting table is better. Keep the mesh flat; warped material changes torch height and encourages the arc to stretch across gaps.
Clamp the sheet at several points, but leave the cut line accessible. A single clamp can allow the panel to vibrate, which causes a rough edge and intermittent arc. Put the work clamp directly on clean bare metal, preferably close to the cut. Expanded metal may have limited electrical contact between strands, so do not assume a clamp attached at the far end will provide a stable path.
If the mesh is painted or galvanized, grind a small clean patch for the ground clamp. Check the torch lead, ground lead, and air supply before starting. Most handheld plasma cutters need dry air at approximately 60 to 100 psi, but use the pressure and flow specified by the machine. Water in the air line causes inconsistent cutting and shortens consumable life.
Plasma-Cutting Technique That Holds the Arc
Set the amperage for the actual material thickness, not the overall thickness of the expanded pattern. For example, a 2 mm strand is still 2 mm steel even if the finished panel is much heavier. Start near the middle of the machine’s recommended range and make a test cut on scrap. Too little current leaves an incomplete underside; too much current makes a broad kerf and destroys tips quickly.
Use a slow, steady travel speed. On expanded metal, rushing across a strand can leave an uncut bridge, while slowing dramatically over every opening can produce excessive dross. Keep the torch approximately 90 degrees to the surface and maintain the manufacturer’s stand-off, commonly around 1 to 3 mm for a drag-shield torch. Do not let the tip ride on the metal unless the shield is designed for dragging.
When approaching a large opening, do not pause at the edge. A pause dumps heat into the strand and can enlarge the end of the cut. Instead, keep moving across the opening and let the pilot arc bridge it. If the main arc goes out, release the trigger, move back onto solid metal, and restart rather than dragging the torch while the machine is repeatedly trying to relight.
For long cuts, make a paper or plywood template and mark the path with a paint marker. Follow the same direction through the diamond pattern instead of zigzagging from strand to strand. A plasma cutter drag shield or guide attachment can make a noticeable difference on thin mesh, but it will not correct a poor ground or wet compressed air.
Consumables, Safety, and Edge Cleanup
Inspect the electrode and nozzle after a few test cuts. A deeply worn electrode, oval nozzle hole, or nozzle packed with spatter can make the arc wander and drop out. Keep spare plasma cutter electrodes and nozzles matched to your torch. Generic consumables may cost less, but poorly fitting parts often create more trouble than they save.
Wear a welding helmet rated for plasma cutting, leather gloves, hearing protection, nonflammable clothing, and safety boots. Fine expanded metal throws hot, sharp fragments in several directions. Shield nearby surfaces from sparks, and check behind the sheet for insulation, wiring, fuel, or other combustible material.
After cutting, knock off dross with a chipping hammer or wire brush. Dress sharp points with a flap disc, but avoid grinding away so much material that the remaining strands become weak. If the edge will be welded, remove paint, zinc, and abrasive residue first. For a structural or load-bearing panel, inspect every strand along the cut; one partially severed strand can be easy to miss and may matter more than a cosmetically rough edge.