This paper describes an on-line computer supported tactile sensor that can recognize complex industrial objects, identify a seam location, and track a three-dimensional seam trajectory for an arc welding robot. A one finger tactile sensor with two degrees of freedom is used. The supporting microcomputer system organizes and reduces the useful sensor data from digitized tactile information to a compact symbolic representation which is matched to a knowledge network. A beam search algorithm is used. The hierarchical organization provides that simple features are first detected on the object, and more complex features are examined later. Pruning of the search tree is based on a likelihood function.