8-1340 - Tweco 8-1340 Switch Shaft for No. 4 MIG Gun

Technical Overview of the Tweco 8-1340 Switch Shaft

The Tweco 8-1340 (also referenced as 1340-1134) is a specialized replacement switch shaft designed for the trigger mechanism of Tweco Classic Series MIG guns, specifically the widely used No. 4 model. As a critical component of the gun's actuation system, this shaft serves as the mechanical interface that engages the electrical switch when the operator depresses the trigger. Manufactured by ESAB under the Tweco brand, this part meets strict OEM dimensional tolerances to ensure smooth operation and prevent binding within the handle assembly.

Over time, the mechanical components within a MIG gun handle can suffer from wear due to repetitive thermal cycling and mechanical stress. A worn switch shaft may lead to inconsistent contact closure, resulting in arc stutter or failure to initiate the weld cycle. Replacing the shaft with a genuine Tweco 8-1340 unit restores the mechanical integrity of the trigger assembly. This component is engineered from durable materials capable of withstanding the harsh environment of industrial welding, including exposure to heat and shop debris.

Installation of the 8-1340 requires disassembly of the MIG gun handle case. It is designed to fit precisely into the molded guides of the Tweco No. 4 handle, aligning perfectly with the trigger blade and the electrical switch block. Maintenance personnel and tool crib managers should verify the specific gun model before ordering, as trigger geometries can vary between Tweco product lines (e.g., Spray Master vs. Classic No. 4). This SKU represents a single unit.