Your plasma cutter can handle different materials at different thicknesses. But the settings that work for 1/4-inch mild steel will not give you a clean cut on 16-gauge stainless or 1/8-inch aluminum. Switch materials without adjusting your setup and you get heavy dross, rough edges, slow cutting, or arc blowout.
This guide gives you a single reference for starting settings across the most common materials hobbyists cut. You get approximate amperage, cut speed, air pressure, and torch height starting ranges for mild steel, stainless steel, aluminum, galvanized steel, and copper or brass. Each table gives a starting range only. Compare it with your machine chart, then test on scrap and fine-tune from there.
A note up front: these are starting ranges, not universal settings. Your machine’s manufacturer cut chart is the final authority for your specific torch, consumables, power supply, air supply, and duty cycle. Use this guide as a cross-reference, then test on scrap before you trust any number in production.
If you are looking for how thick your machine COULD cut: clean cut versus severance capacity. See our article on how thick can a plasma cutter cut. This guide is about the right settings to USE for each thickness and material.
Quick Answer: Plasma Cutting Settings by Material and Gauge
Every material and thickness combination needs a different starting range for amperage, cut speed, air pressure, and torch height. The five tables below give you starting ranges only. Check the chart that shipped with your machine, confirm the consumables and air supply, and test on scrap before you trust any number in production.
Before you use the tables below, confirm the machine chart, consumables, air supply, and duty cycle. Treat the numbers as a first pass only.
Mild Steel: Recommended Starting Settings
| Material Gauge | Thickness (in) | Amperage Range | Starting Speed (approx) | Air Pressure (PSI) | Torch Height |
|---|---|---|---|---|---|
| 24 ga | 0.024 | 15-20A | Fast; steady hand motion | 60-70 | Drag / 1/16″ |
| 22 ga | 0.030 | 15-20A | Fast; steady hand motion | 60-70 | Drag / 1/16″ |
| 18 ga | 0.048 | 20-25A | Moderate-fast | 60-70 | 1/16″ standoff |
| 16 ga | 0.060 | 20-30A | Moderate | 60-70 | 1/16″ standoff |
| 14 ga | 0.074 | 25-35A | Moderate | 65-75 | 1/16″-1/8″ |
| 12 ga | 0.105 | 30-40A | Moderate | 65-75 | 1/16″-1/8″ |
| 11 ga | 0.120 | 35-45A | Moderate-slow | 65-75 | 1/16″-1/8″ |
| 10 ga | 0.135 | 35-45A | Moderate-slow | 65-75 | 1/16″-1/8″ |
| 3/16″ | 0.188 | 40-50A | Slow | 70-80 | 1/8″ standoff |
| 1/4″ | 0.250 | 40-55A | Slow | 70-80 | 1/8″ standoff |
| 3/8″ | 0.375 | 50-65A | Very slow | 70-80 | 1/8″ standoff |
| 1/2″ | 0.500 | 60-80A | Very slow | 75-85 | 1/8″-3/16″ |
| 3/4″ | 0.750 | 80-100A+ | Slow traverse | 75-85 | 1/8″-3/16″ |
Caveat: Amperage ranges assume a quality inverter plasma cutter with a fine-style consumable setup. Budget machines may need settings at the higher end of each range. Always check your machine’s settings chart first. Starting speed is approximate; the correct speed produces a 10-20 degree trailing arc (sparks exiting below the cut at an angle) and minimal dross.
Stainless Steel: Recommended Starting Settings
| Gauge / Thickness | Amperage Range | Speed vs Mild Steel | Notes |
|---|---|---|---|
| 22 ga (0.030″) | 20-25A | ~10% slower | Reduce heat input to minimize discoloration |
| 18 ga (0.048″) | 25-30A | ~10% slower | Clean edges achievable with proper speed |
| 16 ga (0.060″) | 30-35A | ~10% slower | Watch for bottom-edge dross buildup |
| 14 ga (0.074″) | 35-40A | Similar to mild | Dross is harder to remove from stainless |
| 12 ga (0.105″) | 35-45A | Similar to mild | Consider nitrogen for cleaner cuts on thicker stock |
| 1/4″ (0.250″) | 45-60A | Similar or slightly slower | Heavy dross zone; slow speed worsens it |
| 3/8″ (0.375″) | 60-70A | Similar or slightly slower | Clean cut possible at full amperage |
Caveat: Stainless steel retains heat and discolors more easily than mild steel. Avoid pausing during the cut. For cosmetic edges, consider a nitrogen or H35 gas mix if your machine supports it; air plasma works but produces a slightly darker, more oxidized edge.
Aluminum: Recommended Starting Settings
| Gauge / Thickness | Amperage Range | Speed vs Mild Steel | Notes |
|---|---|---|---|
| 18 ga (0.048″) | 25-30A | 20-30% faster | Aluminum dissipates heat quickly; faster speed needed |
| 16 ga (0.060″) | 25-35A | 20-30% faster | Use higher amperage than steel at same thickness |
| 14 ga (0.074″) | 35-40A | 20-30% faster | Clean oxide layer before cutting |
| 12 ga (0.105″) | 40-45A | 20-30% faster | Dross sticks harder to aluminum |
| 1/8″ (0.125″) | 40-50A | ~20% faster | Starting point for most 40-50A machines |
| 1/4″ (0.250″) | 50-70A | ~20% faster | Requires more amperage than steel; heavier machines only |
| 3/8″ (0.375″) | 70-80A | ~20% faster | May hit duty-cycle limits on smaller consumer machines |
Caveat: Aluminum’s high thermal conductivity means it needs 20-30% more amperage than mild steel at the same thickness to maintain the arc. Cut speed must be faster; if you go too slow, the arc extinguishes or produces extreme dross. Clean the oxide layer (aluminum oxide melts at 3,700 degrees F versus the base metal at 1,200 degrees F). For aluminum over 1/4 inch, a high-frequency or pilot-arc torch is strongly recommended.
Galvanized Steel: Recommended Starting Settings
| Gauge / Thickness | Amperage Range | Special Considerations |
|---|---|---|
| 22-16 ga | Use mild steel settings + 5A | Zinc coating can gum up consumables faster |
| 14-10 ga | Use mild steel settings + 5A | Expect more spatter; ventilate well |
| 1/8″-1/4″ | Mild steel settings + 0-5A | Zinc vapor is toxic; use appropriate respiratory protection |
Caveat: Galvanized steel cuts similarly to mild steel at the same thickness, but the zinc coating creates toxic fumes (zinc oxide fever). Always cut in a well-ventilated area or with local exhaust ventilation. The zinc coating may also cause increased spatter on the nozzle and reduce consumable life; clean the nozzle more frequently.
Copper and Brass: General Guidance
| Thickness | Amperage Range | Notes |
|---|---|---|
| Up to 1/8″ | 40-60A | Possible with air plasma but expect high dross and slow speed |
| Over 1/8″ | Not recommended with air plasma | Copper’s thermal conductivity extinguishes the arc; consider mechanical cutting |
Caveat: Copper and brass are notoriously difficult to cut with standard air plasma due to their high thermal and electrical conductivity. Thin material (up to roughly 1/8 inch) is possible with high amperage and fast speed but edge quality will be poor. For anything thicker, a different cutting method (abrasive saw, bandsaw, or laser/waterjet for precision) is recommended.
How to Read This Guide: The Four Settings Explained
Before you use the tables above, it helps to understand what each parameter does and how they interact. You control four main settings: amperage, cut speed, air pressure, and torch height. Each one affects cut quality in a different way.
| Parameter | What It Controls | Too Low | Too High |
|---|---|---|---|
| Amperage | Arc power / penetration | Won’t cut full thickness; heavy low-speed dross | Wide kerf; excessive consumable wear; may blow through thin material |
| Cut speed | How fast the arc moves through the material | Heavy low-speed dross that is hard to remove; wide heat-affected zone | Arc “loses” the cut; high-speed dross (fine, feathery residue on bottom edge); bevel angle increases |
| Air pressure | Arc stability and cooling | Arc flickers or extinguishes; poor cut quality; rapid consumable wear | Arc blows out or becomes unstable; consumes more air than needed |
| Torch height / standoff | Arc voltage / standoff distance | Nozzle contact with work (fine for drag cutting, may cause double-arcing on thicker material) | Arc loses focus; cut becomes wider; bevel increases; dross on bottom edge |
Rule of thumb for speed: The correct cut speed produces a spark stream exiting the bottom of the cut at a 10 to 20 degree angle trailing the direction of travel. Sparks exiting straight down means too slow. Sparks spraying forward or barely coming through means too fast.
The General Rule: Amperage per Thickness
When the tables above do not cover your exact situation, this benchmark gives you a starting point. For mild steel, the rule of thumb is roughly 4 amps per 1/16 inch of thickness.
Mild steel rule of thumb:
- 1/16 inch: roughly 15-20A (or as low as your machine goes for thin sheet)
- 1/8 inch: roughly 30-40A (sweet spot for 40A-class machines)
- 1/4 inch: roughly 40-55A (the rated cut zone for most hobbyist machines)
- 3/8 inch: roughly 50-65A (pushing into upper range of consumer machines)
- 1/2 inch: roughly 60-80A (requires a higher-amperage machine or multiple passes)
Material adjustment factors:
- Stainless steel: Same amperage as mild steel, slightly slower speed
- Aluminum: 20-30% more amperage than mild steel at same thickness, 20-30% faster speed
- Galvanized: Same amperage as mild steel plus 0-5A, same speed
- Copper or brass: 50-100% more amperage (if possible); generally not recommended with standard air plasma
What rated cut versus severance cut means:
- Your machine’s rated cutting thickness (from the manual) is the maximum thickness it can cut cleanly at reasonable speed with standard consumables.
- Severance cut or maximum cutting thickness is the absolute max it can physically cut through, but edge quality will be poor, dross will be heavy, and speed will be very slow.
- The tables in this guide target rated or clean cut settings. Use the upper end of the amperage range for severance cuts and expect to grind.
Fine-Tuning by Cut Quality: What to Adjust When It Is Not Right
No starting point is perfect for every machine and every consumable condition. Read the cut quality and adjust accordingly. This diagnostic table helps you match what you see on the metal to the right fix.
| What You See | Likely Cause | Adjustment |
|---|---|---|
| Heavy dross on bottom edge (hard, lumpy) (low-speed dross) | Travel speed too slow | Increase speed 10-15% |
| Fine, feathery dross on bottom edge (high-speed dross) | Travel speed too fast | Decrease speed 10-15% |
| Heavy bevel on cut edge (one side) | Torch not perpendicular; or torch height wrong | Check torch square to work; adjust standoff |
| Arc flickers or goes out mid-cut | Air pressure too low or inconsistent; consumables worn | Increase pressure by 5-10 PSI; check consumables |
| Cut is wide with rounded top edge | Standoff too high (torch too far from work) | Reduce standoff to 1/16-1/8 inch |
| Excessive spatter on nozzle | Air pressure too low; or consumables at end of life | Increase pressure; replace nozzle or electrode |
| Won’t pierce or initiate cut | Amperage too low for thickness; or air pressure wrong | Increase amperage; verify air supply |
| Edge discoloration (stainless) | Too much heat input | Increase speed; reduce amperage if possible |
| Arc blows out on corners | Speed too slow at corner | Increase corner speed or pause less at corners |
For deeper troubleshooting on dross and edge quality, see our plasma cutter dross troubleshooting guide and our guide on how to get a smooth edge on plasma cut steel.
Duty Cycle Considerations When Pushing Thickness
Cutting thick material at high amperage strains your machine more than most hobbyists realize. Duty cycle is a limiting factor that changes as you push thickness limits.
A machine rated at 60% duty cycle at 40A may drop to 20-30% at 60A. If you exceed duty cycle, the thermal overload cuts power, potentially mid-cut.
Key duty cycle facts for plasma cutting:
- Duty cycle is expressed as a percentage of a 10-minute period (for example, 60% at 40A means 6 minutes cutting, 4 minutes resting).
- Duty cycle decreases as amperage increases. Pushing thickness means more amperage, which means less cutting time before the machine needs to cool.
- At or near maximum rated thickness, expect the duty cycle to drop by half or more compared to the machine’s mid-range rating.
- A machine that can cut 1/2-inch steel at 60A may only sustain 2-3 minutes of cutting before the thermal switch trips.
- For long cuts in thick material, plan cooling breaks or cut in shorter segments.
What to do about duty cycle limits:
- Check your machine’s duty cycle rating at the amperage you plan to use. Most manuals publish a curve or chart.
- If the machine trips thermal overload, let it cool for 10-15 minutes before resuming. Do not keep trying to restart.
- Consider a lower-amperage rough cut pass followed by a cleanup pass if the machine cannot sustain a single full-depth cut.
- Upgrading consumables (fine-cut versus standard) can improve cut quality at a given amperage, potentially letting you cut at slightly lower amperage for the same result, reducing strain on the machine.
Material-Specific Tips for Better Cuts
Each material behaves differently under the plasma arc. These tips help you avoid common mistakes that make settings look wrong.
Mild steel: the baseline
- Most forgiving material for plasma cutting.
- Drag cutting works well up to about 1/8 inch. Beyond that, standoff cutting gives better edge quality.
- Rust and mill scale increase dross. Clean the cut line for best results.
- If you see heavy dross on one side only, your torch is not perpendicular to the work.
Stainless steel:
- Retains heat and discolors easily. Keep moving, do not pause.
- Dross on stainless is harder to remove than on mild steel. A light tap with a chipping hammer works better than grinding.
- For thin stainless (22 ga and thinner), reduce amperage to avoid warping. Use the lowest stable setting.
- Consider a nitrogen or H35 gas upgrade if you cut stainless frequently and need cosmetic edges.
Aluminum:
- The oxide layer is the enemy. Just 0.0001 inch of aluminum oxide acts as an insulator. Clean with a stainless wire brush or chemical cleaner before cutting.
- Aluminum needs more amperage but also faster speed. If you hear the arc struggling, you may be going too slow.
- Dross on aluminum sticks like glue when it cools. Remove it while the cut is still warm if possible.
- Thicker aluminum (1/4 inch and up) creates significant heat in the workpiece. Allow cool-down between cuts to maintain consistent arc behavior.
- For a full deep-dive on this material, see our dedicated aluminum plasma cutting guide.
Galvanized steel:
- Zinc fumes are toxic. Always cut with adequate ventilation. Wear a P100 respirator for extended cutting sessions.
- The zinc coating can deposit on the nozzle face, causing double-arcing. Clean the nozzle more frequently when cutting galvanized.
- The cut edge loses its galvanized coating for about 1/4 to 1/2 inch on either side of the cut. Plan for this if corrosion resistance matters.
- Accept that there will be more spatter. It is normal with galvanized.
Copper and brass:
- Keep expectations realistic. Air plasma is not ideal for these materials. If you must cut them, use the highest amperage your machine can deliver, cut fast, and expect poor edge quality.
- Cutting copper thicker than 1/8 inch with a standard 40-50A air plasma cutter is impractical. The arc extinguishes because copper’s thermal conductivity pulls heat away faster than the arc can deliver it.
- For thin brass sheet (up to 16 ga) you can get acceptable results with a fine-cut consumable set and high amperage.
Air Quality: The Hidden Variable in Plasma Cutting Settings
Dirty or wet compressed air is one of the most common causes of poor cut quality and short consumable life. And it makes your settings look wrong even when they are correct.
Signs your air quality is degrading cut quality:
- Consumables (nozzle, electrode) wearing out faster than expected.
- Arc instability even with correct amperage and pressure.
- Pitting or roughness on the cut edge.
- Green or black deposits on the nozzle.
Minimum air system requirements for plasma cutting:
- Clean, dry air. A refrigerant or desiccant dryer is ideal. At minimum, use a water separator and filter at the machine inlet.
- Adequate flow rate. Check your machine’s CFM requirement at your operating pressure (typically 4-8 CFM at 60-80 PSI for hobbyist machines).
- Proper hose size. Use 3/8-inch ID or larger for runs over 25 feet. Undersized hoses cause pressure drop at the torch.
Choosing the right consumables for your material is covered in our how to select the right plasma cutting consumables guide.
When to Check Your Machine’s Settings Chart Instead
The tables in this guide are cross-machine starting points. Your machine’s manufacturer spent thousands of hours testing their specific torch, consumable geometry, and power supply. Their settings chart is more accurate for YOUR machine.
Where to find it:
- Your machine’s manual.
- A sticker on the inside of the power supply cover.
- The manufacturer’s website or app.
What to do if you cannot find it:
- Search for “[your machine model] cutting chart” or “[brand] plasma settings guide.” Many manufacturers (Hypertherm, Miller, Lincoln, PrimeWeld, Eastwood, Lotos) publish PDFs.
How to use both together:
- Start with the manufacturer’s recommended settings for your machine at the target thickness.
- If you are switching between materials (for example, steel to aluminum), use this guide’s material-specific adjustments to modify from that baseline.
FAQ
Can I use the same settings for all materials at the same thickness?
No. Aluminum needs more amperage and faster speed than steel at the same thickness. Stainless cuts similarly but may need slightly slower speed. Copper and brass are completely different. Each material’s thermal and electrical conductivity changes how the arc interacts.
My machine has a cut chart on the side; should I use that instead of this guide?
Use the manufacturer’s chart as your primary reference and this guide as a cross-check and material-switching aid. The manufacturer tuned their chart for their specific consumables and power supply. If your machine’s chart does not list the material you are cutting (many only list mild steel); use this guide’s adjustment factors to extrapolate.
Why does my 40A machine struggle with 1/4-inch aluminum when it cuts 1/4-inch steel fine?
Aluminum’s thermal conductivity pulls heat away from the cut zone roughly 5 times faster than steel. A 40A arc puts enough heat into steel for a clean 1/4-inch cut, but aluminum needs about 30% more amperage to maintain the arc and enough speed to stay ahead of the heat dissipation. Your 40A machine may still cut 1/4-inch aluminum but expect much slower speed and heavier dross. It is operating at its practical limit.
Conclusion
Keep this guide at your workbench. The key to consistent plasma cutting quality is straightforward.
First, know your machine’s rated capacity from its manual. Second, start with the material-and-thickness settings from this guide. Third, fine-tune by reading cut quality. Fourth, respect your machine’s duty cycle when pushing thickness limits.
No guide replaces your machine’s settings chart. Use this as a cross-reference for material switching and a starting-point generator.
Save or print the reference tables. Check your machine’s duty curve before attempting a long cut in thick material.
For a deeper understanding of plasma cutting capacity, see our guide on how thick can a plasma cutter cut. For troubleshooting dross and edge quality issues, see our dross troubleshooting guide and smooth edge guide. For consumable selection, see how to select the right plasma cutting consumables. For a deeper look at the speed-quality tradeoff, see our cutting speed versus cut quality guide.
