Online Parts Store › Phillips Machine Screw - Flat Head, 5/16"-18 x 2-1/2" Image 1 of 1 Phillips Machine Screw - Flat Head, 5/16"-18 x 2-1/2" $16.00 18-8 Stainless Steel. Add To Cart Added! 18-8 Stainless Steel. You Might Also Like Phillips Tapping Screw - Pan Head, #12 x 1" $40.94 Nylon Insert Locknut - Stainless 12-24 $75.96 Nylon Flat Washer #6, 0.32" Thick, OD 3/8" $17.45 Square Tapping Screw - Oval Head #10 x 1-1/4" $57.05 Phillips Tapping Screws - Flat Head, #12 x 3" $42.89