Online Parts Store › Phillips Machine Screw - Flat Head, 5/16"-18 x 1-1/4" Image 1 of 1 Phillips Machine Screw - Flat Head, 5/16"-18 x 1-1/4" $28.28 18-8 Stainless Steel. Add To Cart Added! 18-8 Stainless Steel. You Might Also Like Lag Screw, 3/8 x 3" $41.46 Stainless Cotter Pin 1/16" x 3/4" $17.76 Phillips Tapping Screw - Truss Head #10 x 1" $33.32 Flat Washer, 1/2", .078" Thick, OD 1-3/8" $74.51 Stainless Countersunk Finishing Washer, #6 $13.10