Abstract: A guard barrier in front of the exposed portion of the blade of a band saw is raised or lowered responsive to the elevation of the portion of the non-planar workpiece which is approaching the blade to be cut so that the varying length of exposed blade is continuously guarded without interfering with the cutting operation. A pneumatic cylinder controls the position of the guard barrier. Cam followers at the bottom end of the barrier ride along the uneven surface of the workpiece acting as a cam and follower movements operate a throttle valve which controls the pressure in the pneumatic cylinder to cause the barrier to move to and hover at its guarding location. An auxiliary valve is provided for rapid raising of the barrier to accommodate a steep rise on the workpiece, to broaden the range of useful operation in relation to workpiece profiles, and for manually controlled lifting of the guard.An electric system is coordinated with the pneumatic system to provide control and safety features.