Importance

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Abstract

A Nitinol element is threaded by first heating it to a temperature of about 800.degree. C., and then applying a threading tool, such as a tap or die, to form the threads. Nitinol has a unique property of increasing yield strength as cold work is applied, but this property ceases to exist above a temperature of about 800.degree. C. The strength of the material at this temperature, however, is sufficient to resist the torque applied by a threading die being screwed onto a Nitinol blank even though it is low enough to permit the Nitinol to flow when the cutting threads of the threading die are forced into the material. At this temperature, the Nitinol is not actually cut by the cutting threads of the tap, die or other threading tool, but instead, the material flows around the cutting threads to form threads in the Nitinol. Since the metal flows into spaces between the threads of the 'cutting' or forming tool, it is necessary to use slightly undersized rod or slightly oversized holes when using conventional dies and taps since no chips are removed.

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First Claim