A kit and method of abrading grain provides multiple components to improve the threshing operation within an agricultural combine. The kit includes a unique concave design, open valley rasp bars, and restrictor plates. The method of abrading grain allows threshing operations for large grains such as corn and, also, for small grains such as soybeans. For example, the kit can be used to facilitate construction of a harvesting system that comprises: a drum of a rotary combine; a straight bar concave in a first position, wherein the straight bar concave utilizing intersecting bars, wherein at least some of said intersecting bars including a sharp leading edge, wherein the sharp leading edge abrades harvested materials and separate grain therefrom when the rotary drum rotates; and a plurality of round bar concaves in at least a second and a third position.