the location of the resin compression layer 42 and the rock 14 surrounding the bore hole 12 likewise with reduced annulus dimensions less resin is required for bonding the bolt 10 within the bore hole 12 with concomitant reduction in the size and quantity of shredded resin packaging film that remains after mixing in one embodiment of the invention the elongated rod 16 is a smooth rod and the polymer coating is produced by molding to create the ridges 52 and spiral threads 50 typically the thickness of the coating is sufficient to minimize the annulus between the resin compression layer and the bore hole wall at less than u215b inch or less than 1 16 inch this reduces the overall weight of the mine roof bolt 10 particularly if the coating is a polymer of low density such as about 2 0 g ml or less referring to fig6 and 7 in accordance with the present invention the mine roof bolt 10 may be installed in a mine roof to provide support to the rock formation 14 in one embodiment of the method of supporting a mine roof the mine roof bolt 10 is installed by inserting a frangible resin cartridge 58 into a bore hole 12 and inserting the mine roof bolt 10 into the bore hole 12 the mine roof bolt 10 includes an elongated rod 16 having a threaded end 18 onto which an expansion assembly 32 is threaded and a drive end 22 extending out of the bore hole 12 a resin compression layer 42.