A mechanism for clamping and holding an elongated workpiece in a machine includes a fixed support, and a longitudinally extending conveyor for supporting the workpiece relative to support. A pair of longitudinally extending clamping members are slidably mounted on the support and are retrained for transverse movement relative to the conveyor. A camming mechanism is actuated by power cylinders to move the clamping members into clamping engagement with opposite sides of the workpiece.