Dewalt #646495-00 Eccentric & Bearing, Fits Model #D28605 Fiber Cement Shear.  Replacement Eccentric Bearing assembly for Motors with a 3/8" Shaft.  Designed for cutting fiber cement Siding & backer board. If the back of your center blade is shaped like the one in the last photo AND your motor has a 3/8" shaft, this is the eccentric bearing you need.