Therm-x Model 300 Welder with Holder

Model 300 is a TIG (tungsten-inert gas) welder that operates in conjunction with a bottle of argon gas and a pressure reducing valve. The energy from an electrical arc flowing through two thermocouple wires raises the temperature of the two wires to their melting point. At the arc's termination, the molten wires cool to form a perfectly welded thermocouple. Since this is not a gas welder, there is no contamination from a third metal used in making the junction nor do air-borne particles or gasses contaminate the weld. The two different wire compositions are completely alloyed in the junction and exhibit less than 0.01°C variation from one thermocouple to the next at the same temperature.

- Easy to use
- Reliable
- Portable
- Repeatable
- Economical

- Wide Range

Dimensions and Specifications

Width: 8 3/4"; Height: 6 1/4", Depth: 6 3/4"

Weight: 10lbs

Power: 115VAC, 60Hz

Lead Time

5 Business Days from Date of Approved Order

For expedited service, please contact Sales Department at (510) 606-1012

Therm-x Model 300 Welder with Holder is available to buy in increments of 1

Product Attachment


The welding of the thermocouple is done by placing the two wires into the wire holder, inserting the holder into the weld cavity, and pressing the WELD push button, starting the following sequence of events:

  1. Argon purges the weld cavity and flows continually.  The Argon flows into the chamber automatically or can be admitted into the weld chamber by pushing the PURGE push button.
  2. A high-frequency field is generated inside the weld cavity, ionizing the argon.
  3. A heavy current (about 12 amps) flows from the tungsten tip to the thermocouple wires starting the welding process.  The start of current flow terminates the high-frequency field.  The argon remains ionized because of the current flow.
  4. The 12-amp welding current continues for about 0.1 second and is terminated by a timing circuit initiated at the start of current flow.

The Model 300 operates equally well with wire from 20 to 40 gauge with the time adjustment on the front panel.  In all cases, a firm, shiny weld is made.  In the case of lighter wire (i.e. 40 gauge), the excess energy contained in the arc is dissipated as heat in the wire holder. The holder acts as a heat sink and as an electrical conduit for the arc. The jaws are made of copper for high thermal conductivity.  The holder must be held against copper weld cavity during the welding period to ensure a return path to ground for the arc.

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