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 Lock Washer, M5 $10.83 Phillips Tapping Screw - Pan Head, #8 x 1/2" $13.86 Phillips Tapping Screws - Oval Head, #10 x 1-3/4" $26.77 Nylon Insert Locknut - Stainless 7/16-14 $21.10 Socket Set Screw 1/4"-20 x 1/4" $26.96