Tool for repairing cross-threading and other damage in threaded blind holes
OwnerVernon L. Fossinventor
Life of this patent
Estimating the term…
Abstract
A slotted inverse tap, compressible for insertion past damaged entry threads in blind holes. (FIG. 1 thru FIG. 5) The tool can be made to smaller sizes than that of prior art. An elongate slot (23) proceeds through a first threaded end (21), then well into a reduced diameter cylindrical body (25). After insertion to the hole bottom, a tabbed shim (28) is inserted to the slot from its side, then pressed down until stopped. The shim (28) enforces mating engagement with undamaged internal threads. A second end of hex and/or squared or other configuration facilitates use of a tap wrench or other tool for rotational extraction. Damaged threads are reformed/re-cut upon rotational withdrawal.
Claims3
A tool for repairing damaged internal threads in blind holes, comprising:
- an elongated tool body with a first end having a short inverse threading tap of the diameter and pitch of the undamaged internal threads in that hole, a second end having a shape suitable to permit engagement and rotation of the body by a rotary drive, an elongated reduced diameter cylindrical body extending from the inverse threading tap toward the second end, the reduced diameter cylindrical body having a diameter slightly smaller than the internal diameter of the threads in the hole, an elongated slot extending from the first end through the threading tap and well into the reduced diameter cylindrical body, the slot permitting the inverse threading tap to be compressed and inserted past the damaged entry threads, the slot also forming two diametrically opposite cutting edges for the threading tap, a tabbed shim with a first portion having the same width of the reduced diameter cylindrical body and a thickness of said elongated slot, the tabbed shim having a second portion forming a laterally extending tab that will seat on the entrance of the internally threaded hole in order to prevent loss of the shim into the threaded hole, and the elongated slot being of a sufficient length for insertion of the shim into the slot after insertion of the tool into the threaded hole.
A method of repairing damaged internal threads in a blind hole, comprising the steps of providing an elongated tool body with a first end having a short inverse threading tap of the diameter and pitch of the undamaged internal threads in that hole, providing a second end having a shape suitable to permit engagement and rotation of the body by a rotary drive, providing an elongated reduced diameter cylindrical body extending from the inverse threading tap toward the second end, the reduced diameter cylindrical body having a diameter slightly smaller than the inside diameter of the threads in the hole, providing an elongated slot extending from the first end through the threading tap and well into the reduced diameter cylindrical body, the slot forming two diametrically opposite cutting edges for the threading tap, compressing the slot to permit the inverse threading tap to be inserted past the damaged entry threads, inserting a tabbed shim with a first portion having the same width of the reduced diameter cylindrical body and a thickness of said elongated slot into the slot in order to expand the threading tap on the internal threads of the hole, seating a laterally extending tab of the shim on the entrance of the internally threaded hole in order to prevent loss of the shim into the threaded hole, and rotating the tool in a direction to withdraw it from the hole in order to reform and recut the damaged entry threads of the hole.
Dependencies are inferred from the claim text.