Online Parts Store › Phillips Machine Screw - Flat Head, 5/16"-18 x 3" Image 1 of 1 Phillips Machine Screw - Flat Head, 5/16"-18 x 3" $18.14 18-8 Stainless Steel. Add To Cart Added! 18-8 Stainless Steel. You Might Also Like Phillips Tapping Screw - Pan Head, #8 x 5/8" $18.01 Stainless Cotter Pin 1/8" x 1-1/2" $55.55 Flat Washer, 5/16", .062" Thick, OD 7/8" $21.67 Stainless Cotter Pin 1/16" x 1" $17.13 Lock Washer, M5 $10.83