A novel method for forming fine-pitch threads in Superinvar

This technical note describes a novel method for forming external threads in Superinvar. Superinvar [Interferometric measurement of the dimensional stability of Superinvar, UCRL-53787, 1988] is a nickel–cobalt steel (64% Fe, 31% Ni, and 5% Co) with a low coefficient of expansion (∼0.5 ppm K−1). This alloy finds application in precision assemblies where thermally induced dimensional changes are of concern. This technical note describes a novel process for the manufacture of high-quality adjustment screws (1/4 in. diameter, 2 in. long, 80 threads per inch—TPI) in Superinvar for use in precision adjustment mechanisms. The quality of the threads produced by this technique is superior to that of threads produced by single-point cutting and compares favorably with commercially produced rolled threads. This technique is best suited to economical production of small quantities.