Miller 320A/BP Welder

The Miller 320A/BP is a legendary, heavy-duty, industrial AC/DC TIG and stick welder. Built like a tank in the 1970s, it is primarily used for precision aluminum and stainless-steel fabrication. Known for its smooth arc and reliability, it uses traditional transformers and spark-gap high-frequency (HF) technology.

Core Specifications

• Rated Output: 320 Amps
• Duty Cycle: 60% duty cycle at 200 Amps
• Primary Input Power: Usually requires heavy 208/230/460V 3-phase power, though some are wired for single-phase.
• Weight: ~850 lbs (massive transformer-based unit)

Key Features

• AC/DC Capability: Features AC for aluminum/magnesium and DC for mild steel, stainless, and other alloys.
• Spark-Gap High Frequency: Uses mechanical spark-gap points for arc starting and stabilization in TIG mode.
• Mechanical Post-Flow Timer: Adjusts how long the shielding gas continues to flow after the arc stops, protecting the tungsten.
• Remote Foot Pedal: Compatible with remote pedals for amperage control during the weld.