Abstract: The apparatus includes a frame structure and a combination grinding and polishing mechanism mounted for horizontal travel thereon. The frame structure includes a bed for supporting welded sheets thereon with the face of the welded seam to be ground and polished facing upwardly. The grinding and polishing mechanism is mounted for horizontal travel on an overhead support beam positioned directly above the bed on which the welded sheets are positioned. The grinding mechanism is comprised of an endless grinding belt rotatably supported between a support wheel at one end where the belt contacts the welded seam and a roller at the other end. The support wheel is mounted for rotation on a pivotally mounted arm and is connected to a drive motor for driving the belt. The motor is mounted with its rotational axis in alignment with the pivot point of the arm. The grinding mechanism further includes a retract mechanism for raising and lowering the grinding belt into and out of its seam grinding position.