Plasma Cutting Guide: Which Metals Can Be Cut (Mild Steel, Stainless, Aluminum, Galvanized) & Maximum Thicknesses

Plasma cutting is a highly efficient thermal cutting process that uses an ionized gas (plasma) to cut through electrically conductive metals with precision and speed. It offers significant advantages over traditional methods such as grinding or oxyacetylene torches, including faster operation, narrower kerf, and reduced heat-affected zones in many cases. However, optimal results depend on selecting appropriate materials, understanding machine limitations, and following best practices for each metal type.

Materials Suitable for Plasma Cutting

Plasma cutting is effective on any electrically conductive material, though it performs best on common metals such as mild steel, stainless steel, and aluminum. Other conductive metals (e.g., copper or brass) can be cut but may require specific gas types or produce suboptimal edge quality.

Mild Steel

Mild steel remains the most frequently plasma-cut material due to its widespread use, cost-effectiveness, and ease of processing. Standard plasma settings—typically referenced from the machine’s manual or cut charts—yield clean cuts with minimal dross when parameters such as amperage, gas type (often oxygen for mild steel), and travel speed are correctly applied.

For galvanized mild steel, which features a zinc coating for corrosion resistance, additional precautions are essential. Cutting galvanized material generates zinc oxide fumes, which can cause metal fume fever—a flu-like condition with symptoms including fever, chills, nausea, and fatigue. In severe cases, prolonged exposure may lead to more serious health issues. Compliance with safety regulations, such as those from OSHA, typically requires respiratory protection like a Powered Air-Purifying Respirator (PAPR) or equivalent, along with effective fume extraction systems.

Galvanized cuts often produce more dross and accelerate consumable wear compared to uncoated mild steel. Many operators prefer to grind away the zinc coating in the cut zone beforehand to improve cut quality and reduce fume hazards, though this partially removes the protective layer and requires dust precautions during grinding.

Stainless Steel

Plasma cutting excels with stainless steel, delivering clean edges when the machine’s capacity matches the material thickness. Nitrogen or argon-based gases are commonly recommended to minimize oxidation and achieve superior cut quality. For precision work, CNC plasma systems are frequently used due to stainless steel’s higher cost and the need for accuracy. Handheld cutting is viable for less demanding applications.

Follow the manufacturer’s recommended settings for stainless steel, as they may differ from those for mild steel. Safety measures mirror those for welding stainless steel: use appropriate ventilation and respiratory protection to avoid inhaling fumes, which may contain hexavalent chromium and other potentially hazardous compounds.

Aluminum

Aluminum’s lightweight, corrosion-resistant properties make it increasingly popular, but its high thermal conductivity requires careful technique to prevent warping or distortion. Excessive heat input can cause rapid expansion in the heat-affected zone, leading to buckling—particularly in thinner sheets.

The key is to maintain a high travel speed while ensuring sufficient heat for penetration. CNC systems simplify this by allowing precise speed control. For handheld operations, practice is essential: test on scrap material to establish a consistent, rapid pace that produces clean cuts without excessive heat buildup. Using a straightedge guide (e.g., a wooden or metal ruler) can improve accuracy and speed during freehand cutting.

Nitrogen or air is often used as the cutting gas for aluminum to reduce oxidation and enhance edge quality.

Cutting Thickness Capabilities

The maximum thickness a plasma cutter can handle depends entirely on the machine’s power output, design, and configuration. Manufacturers specify two primary ratings:

• Recommended (or clean) cut capacity: The thickness at which the machine produces high-quality cuts with minimal dross, good edge finish, and reasonable speed. For example, the Hypertherm Powermax45 SYNC is rated for a recommended clean cut of 16 mm (5/8 inch) in mild steel at approximately 500 mm/min (20 ipm).
• Severance capacity: The maximum thickness the machine can penetrate, though the cut will be rougher, slower, with increased dross and requiring more post-processing. The same Powermax45 SYNC has a severance capacity of 29 mm (1-1/8 inch) for handheld use.

Higher-amperage or industrial systems can handle greater thicknesses—up to 50 mm or more for quality cuts in some cases, and beyond for severance—while handheld units typically max out at lower ranges (e.g., 12–38 mm depending on the model). Always consult the specific machine’s cut charts for material-specific ratings, as performance varies by metal type, gas selection, and torch configuration.

Plasma cutting has established itself as a versatile and practical tool in metal fabrication, often outperforming grinders in speed and oxyacetylene torches in cleanliness and precision. Selecting a reliable machine from a reputable manufacturer ensures consistent performance and longevity. For detailed comparisons of popular models and their capacities, refer to manufacturer specifications or specialized resources.

Plasma Cutting Thickness Chart: Guide to Capacities for Mild Steel, Stainless Steel, and Aluminum

A plasma cutting thickness chart helps determine the suitable material thicknesses a plasma cutter can handle based on its amperage output, material type, and whether you’re aiming for clean (recommended/best quality) cuts or severance (maximum penetration, often rougher with more dross). Ratings vary by manufacturer, consumables, gas type (e.g., air, oxygen, nitrogen), and setup (handheld vs. CNC/table). Always refer to your specific machine’s operator manual or official cut charts for precise settings, including amperage, gas pressure, travel speed, pierce delay, and arc voltage.

General Plasma Cutting Thickness Guidelines by Amperage (Air Plasma, Approximate for Mild Steel)

These are typical ranges compiled from industry sources (e.g., Hypertherm Powermax series, general CNC plasma tables, and fabricator guides). Mild steel generally allows the highest quality thicknesses; stainless steel and aluminum often have reduced clean-cut capacities (slower speeds, more heat sensitivity) when using air plasma.

• ~45 A machines (e.g., entry-level like Powermax45):
  Best quality clean cut: up to ~3/8”–1/2” (10–12 mm)
  Typical pierce: up to ~3/8”
  Severance/max: near ~1” (25 mm)
• ~65 A machines (e.g., Powermax65 SYNC):
  Best quality clean cut: ~1/2”–5/8” (12–16 mm)
  Typical pierce: up to ~1/2”
  Severance/max: ~1”–1-1/4” (25–32 mm)
• ~85 A machines (e.g., Powermax85 SYNC):
  Best quality clean cut: ~5/8”–3/4” (16–19 mm)
  Typical pierce: up to ~3/4”
  Severance/max: ~1-1/2” (38 mm)
• ~105 A machines (e.g., Powermax105 SYNC):
  Best quality clean cut: ~3/4”–1” (19–25 mm)
  Typical pierce: up to ~1”
  Severance/max: ~1-3/4” (45 mm)
• Higher power (125–130 A+):
  Best quality clean cut: ~1”–1-1/4” (25–32 mm)
  Severance/max: up to ~2” (50 mm) or more with industrial systems.

Note: For stainless steel and aluminum, expect 10–30% reduced clean-cut thickness compared to mild steel due to higher reflectivity, thermal conductivity, and oxidation risks. Use nitrogen or specialized gases for better edge quality on non-ferrous metals.

Example Thickness Capacities for Common Machines (Mild Steel Focus)

From Hypertherm Powermax series production cut examples (approximate; check official charts):

• Powermax65 (65 A):
• 1/4” (6 mm): ~116 ipm (high speed)
• 1/2” (12 mm): ~40 ipm
• 5/8” (16 mm): ~26 ipm (clean cut limit)
• Powermax85 (85 A):
• Higher speeds and capacities than 65 A, often up to 3/4” clean with good edge quality.

For thinner materials (e.g., gauge steel), lower amperage modes like FineCut provide finer cuts with less distortion.

Key Factors Affecting Thickness Performance

• Clean vs. Severance: Clean cuts prioritize speed, edge quality, and minimal dross; severance allows thicker material but requires slower speeds and cleanup.
• Material Differences:
• Mild Steel: Easiest and fastest; oxygen plasma boosts performance.
• Stainless Steel: Use nitrogen to reduce oxidation; slower than mild steel.
• Aluminum: High travel speeds to minimize warping; nitrogen or air common.
• Setup: CNC/tables enable consistent speeds and better results on thicker material than handheld.
• Safety & Best Practices: Test cuts on scrap, use proper PPE (especially for galvanized or stainless), and ensure adequate ventilation/fume extraction.

For detailed, machine-specific charts (including speeds, voltages, and consumables), download from manufacturers like Hypertherm (e.g., Powermax SYNC series guides) or consult resources from brands such as Miller, Lincoln, or generic CNC plasma suppliers. View our full line of welding supplies.