Patent ID: 8607670

Claim:
A damaged fastener extractor comprising: a body defining generally cylindrical coordinates ⊖, Z and R about an axis and having a rear body portion communicating with a front body portion; the rear body portion having an outer surface shaped to be engaged by a tool to be used in rotating the body circumferentially about the axis and sized to present a working outer dimension OD to said tool; the front body portion having a front terminus and an inner surface; the front terminus oriented substantially perpendicular to the axis and providing a generally circular receiving aperture communicating with the inner surface; the inner surface shaped to engage a damaged fastener to be extracted and sized to present a working inner dimension ID to the damaged fastener; the front body portion inner surface further having N equally spaced, parallel grooves positioned thereon and oriented to extend along an arcuate, inwardly tapering path from a forward groove terminus located proximal to the front body portion front terminus to a rearward groove terminus located proximal to the rear body portion; each groove having a centerline extending along its length having a pitch P defined by the axial displacement of the centerline per revolution of the centerline about the axis; each groove further having a substantially constant cross-sectional geometry extending along most of its length, whereby the position of each groove centerline at the forward terminus is ⊖ 1 , Z 1 and R 1 and the position of each groove centerline at the rearward terminus is ⊖ 2 , Z 2 and R 2 ; whereby R 1 >ID/2>R 2 ; and an angle of inward taper μ is defined by tan μ=(R 1 −R 2 )/(Z 1 −Z 2 ).