| 摘要 |
An improved tap has a thread cutting portion over which there is a Titanium nitride coating. The Titanium nitride coating has a Rockwell C hardness of at least 70. The body portion of the tap underlying the Titanium nitride coating has a Rockwell C surface hardness of at least 65. This enables the body portion of the tap to provide a rigid support for the Titanium nitride coating. Due to the interaction between the Titanium nitride coating, the relatively hard body portion of the tap, the number of flutes and the cutting face hook angle, the number of holes which can be tapped with a straight fluted tap is increased from 114 to 1,461. On a spiral pointed type tap having a relatively hard body portion interacting with the Titanium nitride, number of flutes and cutting face hook angle, the number of holes increases from 1,662 to 4,758. |
