KP2035-4B1 - Lincoln Electric Long Back Cap for 9 and 20 Series TIG Torches

Product Overview

The Lincoln Electric KP2035-4B1 Long Back Cap is a critical consumable component designed for precision TIG welding applications. Engineered to fit the Lincoln Electric Pro-Torch™ series, specifically the PTA-9, PTA-20, and PTW-20 models, this back cap serves a dual purpose: it secures the tungsten electrode within the collet body and seals the back of the torch head to prevent shielding gas leakage. The 'Long' designation indicates that this cap is hollowed out to accommodate full-length (7-inch) tungsten electrodes, allowing welders to use new electrodes without the need for cutting them down, thereby reducing material waste.

Technical Specifications

Manufactured from high-grade, heat-resistant phenolic or polymer materials, the KP2035-4B1 is built to withstand the radiant heat generated during the gas tungsten arc welding (GTAW) process. It features precision-molded threads that ensure a smooth, secure engagement with the torch body. The integrated O-ring is essential for maintaining the integrity of the inert gas shield (typically Argon), which protects the molten weld pool from oxidation and atmospheric contamination. Failure of a back cap O-ring is a common cause of porosity in TIG welds, making the reliability of this genuine Lincoln part a key factor in quality control.

Compatibility and Usage

This back cap is compatible with industry-standard '9' and '20' style torches, which are among the most common configurations used in light-to-medium duty fabrication and pipe welding. It is not compatible with 17, 18, or 26 series torches, which utilize a different thread size and cap diameter. The KP2035-4B1 is ideal for shop environments where space constraints are not a primary concern, as the long cap extends from the back of the torch. For tight spaces, welders would typically switch to a medium or short button cap, but for general bench work, the long cap is preferred for its ability to house standard tungsten lengths.