993843 - ESAB Tweco ST-21M Steel Liner for 3/64-1/16 Wire

Precision Wire Delivery for Industrial Welding

The ESAB 993843 (Model LINER ST-21M S 3/64 1/16) is a premium replacement component designed to maintain the operational efficiency of high-performance MIG welding systems. Specifically engineered for the ST-21M series of MIG guns—often associated with the Tweco Spray Master line—this liner is critical for the smooth transport of welding wire from the feeder to the contact tip. It is calibrated to handle heavier wire diameters ranging from 3/64 inch to 1/16 inch, making it an essential part for heavy fabrication and structural welding applications where larger wires are standard.

Constructed from high-tensile wound steel, the liner provides the necessary rigidity to prevent collapsing while maintaining enough flexibility to navigate the cable assembly's curvature. The internal surface is finished to minimize friction coefficients, which is vital when pushing thicker wires over long distances. High friction in a worn liner is a leading cause of motor strain, inconsistent wire feed speeds, and burn-back issues. By replacing the liner at regular intervals or when feeding resistance is detected, operators can ensure that the welding parameters set at the power source are accurately delivered to the workpiece.

This component is manufactured to strict tolerances to ensure concentricity with the gas diffuser and contact tip, preventing wire shaving and micro-arcing inside the gun. The 993843 liner is supplied ready for installation, requiring only standard trimming to match the specific length of your gun cable. It is compatible with standard steel wires and flux-cored wires within the specified diameter range. For industrial environments where downtime equates to lost revenue, maintaining a stock of these liners ensures that equipment remains in peak condition and production schedules are met without interruption caused by feeding failures.