Patent ID: 8702364

Claim:
An improved screw fastener for fastening a workpiece to a fixed member, comprising: a screw having a head and a stem, wherein the head is circumferentially provided with knurling and the stem is provided with a first stem portion abutting the head and a second stem portion abutting the first stem portion, the first stem portion being provided with a smooth surface whereas the second stem portion is provided with a threaded surface; a fixed member having a countersink bore section and a threaded bore section for engagement with the threaded surface of the second stem portion, wherein the countersink bore section has a first diameter that is larger than a second diameter of the threaded bore section; and a plastic washer having a hole with an inner diameter that allows the plastic washer to engage with the threaded surface of the second stem portion of the screw and an outer diameter that is larger than the first diameter of the countersink bore section of the fixed member; wherein the second stem portion passes sequentially through the workpiece to be fastened, the plastic washer, the countersink bore section and is engaged with the threaded bore section of the fixed member.