Abstract: A threaded fastener or insert has a generally cylindrical body and about the body is formed a thread. Two sets of flutes are formed in the thread extending axially of the body. One of these sets extends deeper into the thread than the other set.

Abstract: A male screw thread-formed member such as an insert having a thread cutting action has an exterior peripheral portion of substantially full V-thread form along which two or more angularly spaced apart flutes extend from one or both ends of the member, the member being provided with at least one non-helical rib initially of generally annular peripheral V-form at one or both ends thereof and on which is formed a varying reduced V-thread form which follows a helix corresponding to that of the full thread form whereby pointed cutting formations providing peaks of different radial heights and with some of them of offset disposition relative to the helix are formed on the or each rib at the flutes for effecting a distributed thread cutting action thereat, e.g., for use in thermo-setting plastic material.