Tap

Abstract

This article relates to a tap for machining a screw hole. As shown in "Reference Fig. 1 showing a state of use", the article 3 is rotated and inserted into a pilot hole 2 formed in a workpiece 1 to be machined, and a cylindrical guide member 4 formed at the tip of the article 3 fits into the pilot hole 2 without a large gap. Then, by continuing to rotate the article 3 and inserting it into the pilot hole 2, as shown in "Reference Fig. 2 showing a state of use", the guide member 4 brings the threaded portion 5 for cutting in the article 3 into a centered state with respect to the pilot hole 2. This allows the threaded hole to be machined in the centered state. The threaded portion 5 is formed in a plurality of threads along the circumferential direction of the article 3, and a spiral groove 6 is formed between adjacent threaded portions 5, 5. When the threaded portion 5 cuts into the workpiece 1, cutting chips 7 are generated. The cutting chips 7 are transported by the spiral groove 6 as the article 3 rotates, and are discharged outside the workpiece 1. The groove 6 is formed halfway up the cylindrical guide member 4 at the tip side along the length direction of the article 3. This can reliably contain chips 7 generated during machining, particularly at the tip end of threaded portion 5. Groove 6 does not open at the tip of article 3, i.e., the tip of cylindrical guide member 4. This effectively prevents chips 7 from getting into the back of pilot hole 2 and becoming difficult to remove.

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