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 Flat Washer, #6, .032" Thick, OD 3/8" $8.19 Stainless Fender Washer 1/4", .062" Thick, OD 1-1/2 $103.98 Phillips Tapping Screw - Pan Head, #10 x 1-1/4" $32.56 Lock Washer,1/2" $24.75 Phillips Wood Screw - Flat Head, #10 x 1-1/2" $44.84