Self-tapped assembly
AssigneeHubbell Incorporated
InventorsRobert D. Micco, Howard M. Williams, Jr.
Life of this patent
Estimating the term…
Abstract
A tapped hole produced in a metallic material by threading a preselected standard threaded fastener into an untapped hole formed in the material. The diameter of the hole to be formed is determined by using a formula that takes into account the hardness and thickness of the material to be tapped and the basic major diameter and pitch of the preselected threaded fastener to be used to tap the hole. This formula can only be used with threaded fasteners having threads of the Unified Thread Standard type. This formula is particularly useful in tapping a hole formed in a mounting strap of an electrical wiring device.
Claims5
A self-tapped assembly, the combination comprising:
- a metallic material having a predetermined hardness and a predetermined thickness;
- a screw of the Unified Thread Standard type having a predetermined pitch p, a basic major diameter D.sub.o, and a hardness greater than the hardness of the metallic material;
- and
- a circular hole extending into the metallic material, threadedly receiving the screw therein, having threads formed therein by the screw, and having its diameter D sized according to the formula ##EQU3## where x=a variable percentage of thread engagement between the threaded fastener and the threaded hole in the material and ranges from about 0.2 to about 0.6,
- D=hole diameter (inches),
- D.sub.o =basic major diameter (inches)
- p=pitch of thread (inches).
Dependencies are inferred from the claim text.