| 摘要 |
<p>Provided is a spiral tap that obtains durability in the cutting of an internal thread of a difficult-to-machine material such as a heat-resistant alloy such as a nickel-based heat-resistant alloy or a precipitation hardening stainless steel. The spiral tap (10) is provided with: a thread section (12) at which an external thread (16) is formed; a spiral primary groove (22) formed in a manner so as to intersect the thread ridge of the external thread (16); and a secondary groove (26) formed at the tip of the primary groove (22) at a smaller torsion angle than the torsion angle (±) of the primary groove (22). The secondary groove (26) has a positive or negative torsion angle (²) of 0-3°, the cutting edge (24) formed at the ridge between the outer peripheral surface of the thread section (12) and the lateral wall surface (23) facing the tap rotational direction (T) of the secondary groove (26)has a rake angle (S) of -10° to 0°, and furthermore the secondary groove (26) has a groove floor slope (K) of 5-15°. As a result, when machining external threads in a difficult-to-machine material such as a 45 HRC nickel-based heat-resistant alloy, tap life is greatly increased, and a highly durable tap is obtained.</p> |
