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 Phillips Wood Screw - Flat Head, #14 x 3" $73.50 Seachoice Hex Nut, 5/16-24 $58.82 Phillips Tapping Screw - Pan Head, #8 x 3/4" $19.21 Square Tapping Screw - Flat Head,#8 x 1-1/4" $28.68 Stainless Countersunk Finishing Washer, #4 $13.29