Online Parts Store › Phillips Machine Screw - Flat Head, 5/16"-18 x 1-1/2" Image 1 of 1 Phillips Machine Screw - Flat Head, 5/16"-18 x 1-1/2" $30.99 18-8 Stainless Steel. Add To Cart Added! 18-8 Stainless Steel. You Might Also Like Socket Set Screw 10-24 x 1/4" $22.63 Nylon Insert Locknut - Stainless 10-32 $25.51 Phillips Tapping Screw - Truss Head #8 x 1-1/4" $39.30 Stainless Countersunk Finishing Washer, #12 $18.89 Phillips Tapping Screw - Pan Head, #14 x 3/4" $49.38