Abstract: A high speed rotary cutter assembly for cutting sheets of elastomeric materials wherein a rotary blade is affixedly mounted on one end of a spindle and rotates therewith at a rotational speed greater than 2000 rpm. The rotary blade includes a generally planar cutting surface and a tapered back surface to provide a clean cut and minimize abrasion of the cut surface. The rotary blade further includes between 4 and 40 peripheral lobes, each having an attack surface and a trailing surface. The trailing surface is cut more sharply than the attack surface to provide relief to the cut elastomeric material. The spindle includes a spindle bore which communicates cooling air to the rotary blade. The rotary cutter assembly also includes preloaded, permanently lubricated, angular contact ball bearings and a labyrinth seal to provide high speed operation without heat build-up.