Fastener having primary and secondary threads

A fastener having a head and a shank unitary with the head, the shank defining an axis and having a generally cylindrical portion, the generally cylindrical portion having a proximal end adjoining the head and a distal end, the shank having a primary thread formation and a secondary thread formation, the primary thread formation defining axially spaced threads along the generally cylindrical portion of the shank and having a maximum radial dimension at the proximal end, the secondary thread formation defining axially spaced threads between at least some of the threads defined by the primary thread formation, the secondary thread formation originating along the generally cylindrical portion of the shank and having a radial dimension that tapers outwardly so as to increase continuously from the region where the secondary thread formation originates to a region where the secondary thread formation reaches a maximum radial dimension of the secondary thread formation, the region where the radial dimension of the secondary thread formation reaches the maximum radial dimension thereof being spaced axially from the proximal end, the secondary thread formation being interrupted.

A fastener having a head and a shank unitary with the head, the shank defining an axis and having a generally cylindrical portion, the generally cylindrical portion having a proximal end adjoining the head and a distal end, the shank having a primary thread formation and a secondary thread formation, the primary thread formation defining axially spaced threads along the generally cylindrical portion of the shank and having a generally uniform radial dimension along the generally cylindrical portion of the shank, the secondary thread formation defining axially spaced threads between at least some of the threads defined by the primary thread formation, the secondary thread formation having a radial dimension that tapers outwardly and continuously so as to increase continuously from a region where the secondary thread formation originates to a region at the proximal end where the radial dimension of the secondary thread formation reaches a maximum radial dimension, which is less than the generally uniform radial dimension of the primary thread formation along the generally cylindrical portion of the shank, the secondary thread formation being interrupted.

A fastener having a head and a shank unitary with the head, the shank defining an axis and having a generally cylindrical portion, the generally cylindrical portion having a proximal end adjoining the head and a distal end, the shank having a primary thread formation and a secondary thread formation, the primary thread formation defining axially spaced threads along the generally cylindrical portion of the shank and having a generally uniform radial dimension along the generally cylindrical portion of the shank, the secondary thread formation defining axially spaced threads between at least some of the threads defined by the primary thread formation, the secondary thread formation having a radial dimension that tapers outwardly and continuously so as to increase continuously from a region where the secondary thread formation originates to a region at the proximal end where the secondary thread formation reaches a maximum radial dimension, which is less than the generally uniform radial dimension of the primary thread formation along the generally cylindrical portion of the shank, the secondary thread formation originating near the distal end of the generally cylindrical portion of the shank.