An orthopaedic surgical instrument (10) including a polymer 4-in-1 femoral cutting block (12) having a chamfer cutting slot (36) defined therein, and a chamfer cutting guide assembly (50) secured within the chamfer cutting slot. The chamfer cutting guide assembly includes a first planar surface (52), a second planar surface (76) spaced apart from, and extending parallel to, the first planar surface, a third planar surface (80) connected to the second planar surface and extending at an angle relative to the first planar surface and a fourth planar surface (54) connected to the first planar surface and extending parallel to the third planar surface. The first planar surface and the second planar surface define a first metallic planar cutting guide, and the third planar surface and the fourth planar surface define a second metallic planar cutting guide. The chamfer cutting guide assembly may include a pair of metallic bushings (56, 58).
