A split re-threading die includes two halves pivotally attached to each other and defining a through-bore and a hexagonal external surface when closed. Each half has inward facing teeth at the free end. The through-bore is configured to receive an externally threaded fastener to be re-threaded and the hexagonal external surface is configured to be received within a mechanical socket. The teeth rethread the fastener as the die is turned and the teeth traverse the threads of the fastener.

A machining device threads a workpiece by relatively rotating the workpiece and a multi-blade tool and relatively moving them along a feed direction to perform cutting processes in the radial direction of the workpiece along the same cutting path in a predetermined spiral form. A controller performs a groove machining to form a threaded portion with vibration in the radial direction of the workpiece and a finish machining to form the threaded portion by bringing the multi-blade tool into contact with the grooved portion of the workpiece. The multi-blade tool has a first cutting blade and a second cutting blade arranged side by side along the feed direction. The controller sets amplitude of a vibration waveform to a value at which a cutting edge of the second cutting blade does not come into contact with the screw bottom surface of the workpiece in the finish machining.

A thread repair tool for rethreading a blind tapped hole having damaged threads above undamaged threads of the hole, including: a shaft having a plurality of curved surfaces that extend from a top end of the shaft to a bottom end of the shaft, the plurality of curved surfaces being concave with respect to an exterior perimeter of the shaft; and wherein the shaft has a plurality of corner portions, each one of the plurality of corner portions being located in between two of the plurality of curved surfaces, a first pair of the plurality of corner portions extending from the top end to the bottom end, and a second pair of the plurality of corner portions having a threaded area proximate to the bottom end, the first pair of the plurality of corner portions being adjacent to each other and the second pair of the plurality of corner portions being adjacent to each other.

The invention relates to means for repairing male threads. The thread repair tool (1) comprises the first tool body (2), the second tool body (3), and the rollers (4, 6) installed on said tool bodies (2, 3), respectively. The first tool body (2) and the second tool body (3) are movably connected to each other at their first ends (2.1, 3.1), and each said tool body (2, 3) has a cambered shape thus forming a ring-like shape when the thread repair tool (1) is in a closed state. The technical result of the invention is repairing a male thread upon re-forming a material of the thread and avoiding cutting thereof, while keeping a diameter of the male thread of a required value.