Opposite threaded stud

A fastening assembly for a plastic workpiece comprising in combination a double ended stud with a coaxially aligned upper and lower shank portions and an outwardly extending flange intermediate said shank portion, said flange having substantially planar upper and lower surfaces, said upper shank portion being threaded in one direction and said lower shank portion being threaded in the opposite direction from the upper shank portion, said lower shank portion thread being provided with a cutting edge and extending from substantially the end of the lower shank to the flange, said lower shank portion being threaded in a blind bore in a workpiece, the depth of the bore in said workpiece being substantially equal to the length of the lower shank portion so that the end of the lower shank abuts the end of the blind bore when the stud is fully secured in said workpiece with the lower surface of the flange abutting the threads of the workpiece bore, a structure mounted on the upper surface of said flange and defining an aperture therein through which said upper shank portion protrudes and fastening means mounted on said upper shank and threadably engaging said upper shank with the lower surface of said fastening means engaging said structure to hold said structure against said flange, the initial back off torque of said fastening means when rotated to remove it from said upper shank after engaging said structure tightening said lower shank in said workpiece.

A method of fastening an apertured structure to a plastic workpiece with a plurality of performed bores and later removing the structure from the plastic workpiece comprising the steps of:

• (a) rotating a plurality of threaded studs each of which is formed with oppositely threaded upper and lower shank portions and a laterally extending flange therebetween into the plastic workpiece bores until said flange contacts said plastic workpiece,
• (b) placing a structure defining a plurality of apertures over said upper shank portions so that said structure covers the adjacent surface of said flanges and abuts the surface of said flanges with said upper shank portions extending through said structure and beyond said structure,
• (c) threading a plurality of nuts onto the upper shank portion in an opposite direction from the direction in which the lower shank portion was threaded into the plastic workpiece until each nut fits snugly against said structure and holds said structure together against the upper surface of said flanges, and
• (d) rotating said nuts in an opposite direction than the direction in which they were threaded on said upper shank portion to transmit the starting torque forces to said flange and tighten said lower shank portions in said plastic workpiece.

A fastening assembly for a plastic workpiece having a plurality of performed bores comprising in combination at least two double ended studs, each of said studs comprising coaxially aligned upper and lower shank portions and an integral outwardly extending flange located substantially intermediate said shank portions, said flange having substantially planar upper and lower surfaces and an outer surface forming drive means, said upper shank portion being threaded in one direction and said lower shank portion being threaded in the opposite direction, said shank portions being threaded from the outer end to the flange, said lower shank portion of each stud being threaded into a bore of a plastic workpiece by rotating said drive means until the lower surface of the flange abuts the plastic workpiece, a planar surfaced structure mounted on the upper surface of said flanges and defining a plurality of apertures therein through which said upper shank portions protrude and fastening means mounted on each upper shank and threadably engaging said upper shank so that upon rotation of the fastening means, the lower surface of the fastening means engages said structure to hold said structure against the stud flange with the plurality of studs preventing rotation, each fastening means being threaded on said upper shank and tightened against said structure, each said fastening means when initially rotated to remove it from said upper shank after engaging said structure tightening said lower shank in said workpiece.