Plasma Cutting Thickness Guide: Steel, Aluminum & Stainless

In the world of metal fabrication, the plasma cutter is the "Swiss Army Knife" of the workshop. Whether you are a hobbyist working in a garage or an industrial engineer overseeing a CNC production line, the question remains the same: "Will this torch cut through my material?"

Understanding the relationship between amperage, gas types, and material conductivity is vital for clean, dross-free cuts. In this ultimate guide, we break down the cutting capacities for the three most common metals: Carbon Steel, Stainless Steel, and Aluminum.

1. Understanding Plasma Cutting Fundamentals

Before we look at the charts, we must understand why different metals require different power levels. A plasma torch works by passing an electric arc through a pressurized gas (like air, nitrogen, or argon), creating a "plasma" state that melts metal and blows it away.

The Role of Amperage

Amperage is the primary driver of cutting capacity.

• Low Amperage (15–30A): Ideal for thin sheet metal and HVAC work.

• Mid-Range (40–80A): The "sweet spot" for general fabrication and maintenance.

• High Amperage (100A+): Required for heavy industrial plates and thick structural steel.

Rated Cut vs. Severance Cut

When looking at manufacturer specs, you will see two terms:

1. Rated Cut: The thickness the machine can cut at a high quality (10 inches per minute or more) with a clean edge.

2. Severance Cut: The absolute maximum thickness the machine can push through. The cut will be slow, messy, and require significant grinding afterward.

2. Carbon Steel: The Gold Standard for Plasma

Carbon steel is the easiest material to cut with plasma. Because it is highly conductive and has a relatively low melting point compared to its structural integrity, plasma torches perform at their peak efficiency here.

Thickness Capacities by Amperage (Carbon Steel)

Why Carbon Steel is Easier

Unlike aluminum, carbon steel doesn't dissipate heat as quickly, allowing the plasma stream to stay focused. Most entry-level 110V/220V dual-voltage cutters are optimized specifically for 1/4" to 1/2" carbon steel.

3. Stainless Steel: The Heat Challenge

Stainless steel is a different beast. It has a higher melting point and a chemical composition (chromium/nickel) that makes the molten metal "stickier."

Thickness Capacities by Amperage (Stainless Steel)

The "Dross" Factor

When cutting stainless, you will often notice dross (hardened slag) on the bottom of the cut. To achieve the maximum rated thickness on stainless, professionals often switch from compressed air to Nitrogen or an Argon-Hydrogen mix to prevent oxidation and ensure a "silvery" finish.

4. Aluminum: The High-Conductivity Hurdle

Aluminum is notoriously difficult for plasma cutters. Because aluminum is an incredible conductor of heat, it sucks the energy away from the plasma arc faster than steel does.

Thickness Capacities by Amperage (Aluminum)

Pro-Tip for Aluminum

To cut thicker aluminum, you need more speed. If you move too slowly, the heat dissipates into the surrounding plate, causing the edge to melt and deform. Always aim for a machine that is "over-specced" by 20% for your aluminum needs.

5. Factors That Affect Cutting Performance

The "rated thickness" on the box isn't the only thing that matters. Several external factors can reduce your cutting capacity by up to 30%.

Air Quality and Pressure

If your compressed air contains moisture or oil, the arc will flicker, and your consumables (nozzle/electrode) will burn out instantly. Using a dedicated air dryer is mandatory for thick-plate cutting.

Consumable Condition

A worn-out nozzle will create a "wandering" arc. If your torch is rated for 1/2" but struggles with 3/8", check your orifice. A perfectly round hole is required for maximum penetration.

Standoff Distance

For manual torches, maintaining a consistent 1/16" to 1/8" distance from the plate is crucial. Using a drag shield or a standoff guide ensures that the arc stays concentrated on the metal.

6. How to Choose the Right Plasma Cutter for Your Needs

For the DIYer / Artist

If you are cutting 16-gauge sheet metal or the occasional 1/4" bracket, a 30-40 Amp inverter-based cutter is sufficient. These are portable and often run on standard household outlets.

For the Fabrication Shop

For heavy-duty bumpers, trailers, or machinery repair, look for a 60-80 Amp unit. This ensures you can cut 3/4" steel all day without hitting the "Duty Cycle" limit.

For CNC Industrial Use

High-definition plasma systems (130A to 400A) are required for automated tables. These systems use sophisticated gas consoles to switch between Oxygen (for steel) and H35 (for thick stainless/aluminum).

Conclusion: Matching Power to Projects

The thickness of the metal you can cut is a direct reflection of your machine’s amperage and the type of material. While a 50A cutter handles 1/2" Carbon Steel with ease, it will struggle with 1/2" Aluminum. Always choose a machine based on your frequent cutting thickness, not your maximum severance thickness.

Ready to upgrade your workshop? Whether you're looking for precision or raw power, choosing the right torch starts with understanding your materials.