How to Change the Liner on a MIG Welder: A Comprehensive Guide

Changing the liner on a MIG welder is a crucial maintenance task that ensures optimal wire feeding and welding performance. This comprehensive guide will walk you through the advanced steps to replace the liner in your MIG welder, providing in-depth technical details and expert-level insights to help you tackle this task with confidence.

Preparation: Ensuring a Smooth Liner Replacement

Before you begin, it’s essential to properly prepare your MIG welder for the liner replacement process. Start by ensuring the power supply is turned off and the gun is removed from the feeder. Next, remove the nozzle, contact tip, and gas diffuser. Depending on the type of power pin your welder uses, you’ll need to either loosen the liner set screw using a 5/64 inch Allen wrench or turn the thread-in liner collet counterclockwise with a 10-mm wrench to free the liner from the power pin.

Removing the Old Liner: Careful Extraction

how to change the liner on a mig welderImage source: Mig weld example

With the necessary components removed, it’s time to extract the old liner. Straighten the gun and grip the conduit liner with a pair of pliers, then gently pull it out. Be cautious during this step to avoid kinking or damaging the liner.

Installing the New Liner: Precision Feeding

Now, it’s time to install the replacement liner. Feed the new liner through the gun, using short strokes to prevent kinking. If necessary, twist the liner clockwise as you feed it through. Depending on the power pin design, you’ll need to either:

  1. Liner Set Screw: Seat the liner retainer with o-ring to the shoulder inside the bore of the power pin, then secure it by tightening the liner set screw. Avoid overtightening.
  2. Thread-in Liner Collet: Use a 10-mm wrench to turn the thread-in liner collet in a clockwise direction and tighten it in the power pin.

Trimming the Liner: Achieving the Perfect Length

With the new liner in place, it’s time to trim it to the correct length. Push the liner back into the gun and hold it in position. Use a Liner Gauge to trim the conduit liner, ensuring a 3/4″ (20 mm) stick-out. If you’re using a 154 or 454-1 retaining head, the liner should be trimmed to a 1/2″ (13 mm) stick-out. After trimming, be sure to remove any burrs that could obstruct the wire feed, especially on flat wire type conduit liners.

Reassembling the Gun: Putting It All Back Together

The final step is to reassemble the MIG gun. Replace the nozzle, contact tip, and gas diffuser onto the neck, ensuring a secure and proper fit.

Advanced Tips for Liner Maintenance

To keep your MIG welder running at its best, consider the following advanced tips:

  1. Replace the Liner Proactively: Replace the liner when you start experiencing wire feeding problems, as this can indicate wear or damage.
  2. Avoid Liner Abuse: The quickest way to ruin a liner is by running dirty or rusty wire through it, which can lead to premature wear. Additionally, be mindful of kinking the liner or dropping objects on it, as these actions can also cause damage.
  3. Proper Liner Storage: When not in use, store the liner carefully to prevent kinking or other forms of damage that can occur during transportation or job site conditions.

By following these advanced steps and incorporating the expert-level tips, you’ll be able to effectively change the liner on your MIG welder, ensuring optimal wire feeding and welding performance for your projects.


  1. How to Install or Replace a Conventional Liner
  2. MIG Welder Liner Replacement
  3. How to Replace a MIG Welder Liner