A sheet metal bending brake having a frame with a planar work supporting surface and a plurality of spaced frame members extending over the work support surface. Each frame member has a throughbore and these throughbores are aligned with each other. A plurality of elongated pivot arms are pivotally secured at one end to the frame for movement toward and away from the work supporting surface. Each pivot arm also includes a generally rectangular opening aligned with the frame member throughbores. A block is longitudinally slidably mounted in each pivot arm opening and this slide block is constrained against movement in a direction perpendicular to the work support surface. Each block furthermore includes a trapezoidal opening with spaced apart and parallel top and bottom surfaces and outwardly flared side surfaces. An elongated shaft extends through and is rotatably mounted to the frame member throughbores and this shaft also extends through the trapezoidal openings in the pivot arms. A plurality of eccentric cams are secured to the shaft so that one cam is associated with and positioned within each trapezoidal opening. This cam is dimensioned so that the cam contacts the outwardly flared side surfaces of its associated slide block regardless of the rotational position. Pivotal movement of the shaft thus displaces the pivot arms in a direction generally perpendicular to the work support surface due to the coaction of the eccentric cams with the side surfaces of the slide blocks.