PTA Surfacing Tunnel Shield Blades Tunnel shield inserts are critical components in the tunnel boring industry. The cutter rings are designed to withstand high loads and vibrations while maintaining precise cutting performance. To ensure that tunnel shield blades operate efficiently and extend their service life, it is essential to properly maintain and replace cutting tools and worn cutter heads. PTA Surfacing Tunnel Shield Blades is a very effective maintenance method that is cost effective, efficient and has excellent performance compared to other repair methods. Shield blades can be welded using automated PTA surfacing, equipped with a real-time monitoring system.