Material Thickness Guide: What Your Plasma Table Can Cut

The Five Variables That Determine Thickness

1. Amperage & Power Source Class
   Higher amperage increases energy density at the arc, enabling thicker pierces and sustained travel speed. Think in common classes: ~45 A, 65 A, 85 A, 105 A, 125–130 A.

2. Process Gas & Consumables

• Air (general purpose): economical, good on mild steel, acceptable on stainless/aluminum with some nitriding/discoloration.

• O₂ (steel): cleaner edges and faster speeds on mild steel.

• N₂ / F5 / Mixed (stainless/aluminum): improved edge appearance and dross control.
  Consumables (nozzles/electrodes) must match amperage and gas.

3. Torch Height Control (THC) & Standoff
   Accurate pierce height, cut height, and arc voltage sampling keep kerf consistent across plate warp and small heat movement.

4. Machine Mechanics
   A rigid frame and true linear guidance reduce vibration, improving edge smoothness and hole roundness—especially noticeable on thicker plate.

5. Air Supply Quality
   Dry, oil-free air preserves consumables and keeps the beam stable. Wet or dirty air shortens life and degrades edges.

Quick Reference: Typical Air Plasma Ranges (General Guidance)

Notes: Values below are typical, not brand-specific. “Best quality” = routine production with consistent edges and reasonable cleanup. “Sever” = occasional separation cut at slow speed with heavy cleanup.

Stainless & Aluminum: Expect slower speeds and slightly reduced best-quality thickness versus mild steel when using air. With optimized gas (e.g., N₂ or mixed gases), edge quality can improve.

Material-Specific Guidance

Mild Steel (A36 and similar)

• Best value in air or oxygen for speed and cost.

• For <1/4″ sheet, even a 45 A class source can cut very quickly with fine features.

• For 1/4″–1/2″, 45–65 A covers most general fabrication.

• For 1/2″–3/4″, consider 65–85 A for better pierce reliability and throughput.

• For 3/4″–1″, 85–105 A keeps speeds reasonable and edges consistent.

• >1″ is possible with 105–130 A, but plan for lower speeds and more heat input.

Gas tip: O₂ on steel improves speed and edge appearance vs. straight air, but follow torch manufacturer guidance on gas kits and consumables.

Stainless Steel (304/316)

• Air plasma works, but edges can show nitride tint.

• N₂ or specialty mixes improve edge color and reduce dross on thicker sections.

• Derate “best-quality” thickness by a small step vs. mild steel when using air.

Aluminum (5052/6061)

• Air is acceptable; N₂ can help on thicker plate.

• Heat input and expansion are higher—watch pierce delay and lead-in strategy.

• Expect slightly lower best-quality thickness and slower cut speeds than steel at the same amperage.

Choosing a Power Class for Your Work Mix

Ask three questions:

1. What thickness do you cut every day?
   Size the system to make your daily thickness fast and clean—not the rare job.

2. What’s your max routine thickness?
   Pick a class that can pierce and traverse that thickness without crawling.

3. Do you need headroom?
   If you occasionally hit heavier plate, verify the occasional sever capability, but budget time for slower speeds and extra cleanup.

Simple rule of thumb: If your routine parts live at the top end of a power class, move up one class to improve pierce reliability, hole quality, and consumable life.

Piercing vs. Edge-Starting

• Piercing is the limiting factor on thicker plate because it concentrates heat and ejects molten metal toward the nozzle.

• Edge-starting allows you to separate thicker stock than you can pierce, but it’s not practical for nested production parts.

Protect the torch: Use correct pierce height/time and a lead-in that keeps spatter away from the nozzle. Replace worn consumables early—waiting too long costs more in scrap and rework.

Setup Details That Move the Needle

• THC setpoints: Keep pierce height higher than cut height; verify arc voltage sampling on straight segments.

• Lead-ins/outs: Use longer, outside lead-ins on thick plate; employ bolt-hole routines for holes under ~1.2× kerf.

• Kerf compensation: Calibrate by thickness; don’t reuse thin-sheet kerf on 3/4″ plate.

• Cut speed: Listen for a steady arc; too fast leaves top bevel, too slow builds bottom dross and wide kerf.

• Air quality: Dryer + filter. Moisture is the silent consumable killer.

Practical Thickness Targets by Shop Type (Examples)

• General fab / ag / repair: Daily cuts ≤ 3/8″, frequent 1/2″ → 45–65 A.

• Structural brackets / off-road / job shop: Daily 1/4″–1/2″, frequent 5/8″–3/4″ → 65–85 A.

• Heavy fab / plate: Daily 1/2″–1″, frequent 3/4″–1″ → 85–105 A.

• Occasional 1–2″ separation with routine sub-1″ work → 105–130 A, plan for slow severing on the thickest jobs.