Online Parts Store › Phillips Machine Screw - Flat Head, 5/16"-18 x 1-1/4" Image 1 of 1 Phillips Machine Screw - Flat Head, 5/16"-18 x 1-1/4" $28.28 18-8 Stainless Steel. Add To Cart Added! 18-8 Stainless Steel. You Might Also Like Nylon Insert Locknut - Stainless 5/16-24 $46.35 Phillips Tapping Screws - Flat Head, #12 x 3" $42.89 Nylon Insert Locknut - Stainless 1/4-20 $27.84 Phillips Tapping Screws - Flat Head, #8 x 5/8" $12.41 Socket Set Screw 10-24 x 1/4" $22.63