186W59 - CGA-320 Regulator Inlet Nut for CO2

Get Your MIG Welder Back Up and Running

If you are setting up a MIG welder for solid wire welding on mild steel, you are likely using 100% CO2 or a CO2 mix. The ESAB C-59 Nut is the specific part you need to connect your gas regulator to a standard CO2 shielding gas cylinder. We've all been there—you go to swap out a tank, and the nut on your regulator is either rounded off from using the wrong wrench, or the threads are looking a bit chewed up. A compromised nut can lead to gas leaks, which not only wastes expensive shielding gas but can also cause porosity in your welds due to insufficient coverage. Replacing a worn nut is a cheap and easy fix that ensures your welding setup remains airtight and efficient.

This nut is built to the CGA-320 standard, which is the dedicated fitting for Carbon Dioxide. It is made from solid brass, so it stands up to the wear and tear of the shop environment. It features a standard hex shape that fits your cylinder wrench perfectly, allowing you to get the leverage you need to crush that sealing washer just right. Remember, unlike Argon fittings (CGA-580) which seal metal-to-metal, CO2 fittings (CGA-320) require a small plastic or fiber washer to create the seal. This nut acts as the clamp that holds everything together. It slides over the tailpiece of your regulator and screws directly onto the external threads of the tank valve.

Don't let a stripped fitting stop your project. Keep a spare C-59 nut in your toolbox or parts bin. It is compatible with most major brands of regulators, including Victor, Harris, Miller, and Lincoln, provided they are set up for CO2 service. Whether you are a hobbyist working in your garage or a professional welder on the line, having the right fittings ensures safety and quality. This simple brass nut is the bridge between your gas supply and your machine, playing a small but crucial role in laying down perfect beads.