All You Need To Know About Plasma Cutting And Gauging

All You Need To Know About Plasma Cutting And Gauging

Plasma is a state of matter formed by ionizing gas and making it electrically conductive.

What is Plasma Cutting?

Plasma cutting is a method being increasingly used in industries to cut various types of metals. The plasma for cutting is created by adding energy to an electrically neutral gas like compressed air. When energy in the form of electricity is passed through compressed air, the gas is electrically imbalanced and can thus conduct electricity like wire. Plasma is formed as a result of this process and it gets hotter as more energy is passed through it.

By controlling the plasma and concentrating it into a smaller area, then adding air pressure and intensifying with higher voltage Miller Welders have created an arc that does more than just melt metal. They have created an arc to blast through and blow away the cuttings.

By adding compressed air and electrical power to the plasma torch, electrical conductive materials can be cut or pierced very precisely and quickly as no pre heating is required. Metals like aluminum, stainless steel, brass and titanium can be cut individually or even stacked together if needed.

Air Plasma Cutting



Air plasma cutting uses air instead of other expensive gasses. However, it requires a special electrode containing hafnium or zirconium mounted in a copper holder. At Millers they use hafnium in a copper holder for an electrode.

Equipment Needed

The various equipments required for air plasma cutting are:

  • A power source designed for plasma cutting. Typical models range from 12 Amps systems which is used to sever a quarter inch mild steel. While heavy duty industrial models range from an output of 100 Amps or more, with an ability to cut an inch and a quarter of material.
  • Input power requirement may vary from a regular household wall outlet to a 3 phase Ac power.

Plasma Torch

Development of a plasma cutting torch is the key to the success of this process. The components used shape and constrict a high pressure air stream to a very small diameter. When ionized, this stream will become the plasma that conducts electricity at voltage level required to cut metal. The various components used are, a tip and an electrode, a swirl ring, an epoxy cup to enclose the parts and a standoff or a drag shield.


When the torch shield is depressed, the arc starts as either as a

  1. High frequency arc where a brief high frequency pilot arc jumps the gap between the torch tip and electrode
  2. Pilot Arc which is created when both the internal components of the arc come into a brief contact, thereby causing a very brief short circuit

Pilot arcs maintained as electricity flows between the tip and the electrode, start the air stream ionization process and plasma is created. Now the plasma arc emanates from the electrode and current is conducted between the work piece and the electrode through the hole in the torch tip, thus transferring the heat to the work piece. At the point of contact, the metal is liquefied, melted and blown away. A regulated supply of compressed air at a fixed pressure is required for this process. The pressure may vary from 50-90 psi, depending on the torch lead length and the plasma system in use.


  • Use full face helmets or face shields to protect your eyes
  • While using the plasma torch, point it away from the body as the heat from the arc can cause severe burns
  • A complete electrical circuit is present from the power source and torch, through the arc while cutting, through the piece, work piece clamp and cable and back to the power source. Plasma cutting requires higher voltages than wielding, hence requiring more caution
  • Always switch off the power before removing the work piece clamp or dismantling the torch
  • Plasma cutting produces extremely hot molten metal, hence make sure there are no flammable material close-by and allow the tip to cool before touching


  • First check if all the parts of the torch are assembled properly and free of debris. Also check the air pressure and set the power source controls as instructed in the user manual
  • Switch on the power and if your amperage is above 40 Amps, position the tip of the torch above and at the edge of the material to be cut, at the distance recommended by the manufacturer. If amperage is below 40 Amps, the tip may be set in contact with the work piece
  • Press the trigger to start the pilot arc and when the cutting arc begins, pull or push the torch, across the arc slowly to make the cut. Make sure to maintain the required gap between the tip and the metal throughout the procedure
  • If the sparks go through the metal and to the bottom of the kerf, your cutting speed is correct. If the sparks splash back, you are going too fast.
  • If the arc does not penetrate the metal or if your speed is low, make necessary amperage adjustments only after extinguishing the arc by releasing the trigger
  • Make sure the work clamp is secure and close to the cut
  • At the end of the cut, pause briefly and allow the pieces to separate before releasing the trigger

Air Plasma Gauging

Gauging can be performed using the same power source and torch but the parts of the torch need to be changed. Replace the drive shield and the standing tip must be replaced with a special gauge tip and a gauge shield.

Tilting the torch at 40-45 degrees to the work piece will start the gauging process. Twist the torch into the gauged area while blowing the material out of the gauge. Any electrical conductive material can be easily gauged.


Plasma cutting saves you a lot of time and is safe as there are no flammable gases used. It is a simple solution to most of your metal cutting needs.

See Also:

The Choice for a CNC Plasma Cutter

Tips in using a plasma cutter

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