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 Screws - Flat Head, #8 x 1" $18.01 Nylon Flat Washer 3/8", 0.62" Thick, OD 1" $57.19 Flat Washer, 5/16", .062" Thick, OD 9/16" (A/N Style) $10.20 Phillips Tapping Screw - Pan Head, #10 x 5/8" $24.31 Phillips Self Drilling Screw - Pan Head #10 x 3/4" $36.40