An adjustable rotary dado blade assembly of the type designed to be mounted for relatively high speed rotation on an arbor or the like and including mounting means in the form of at least two cam assemblies movably engaging one another and the blade itself so as to position the blade in engagement with a positioning surface, the configuration of which defines the angular orientation of the plane of the blade relative to the axis of rotation of the blade. The blade means includes a disc having a plurality of cutting elements formed about the periphery in unequal spaced relation to one another and located so as to position the cutting edge of the cutting elements at different radial distances from the center of the blade disc so as to provide a substantially level dado.