Use solid carbide taps for long life. Standard size tap drills should be satisfactory. External threads are formed best, not with conventional thread-cutting dies but by lathe turning or grinding, with light feeds and shallow cuts. Surface finishing of flat sheets, etc. is best performed with a Blanchard grinder. Sheet size is limited by the size of the machine.
Coolants Use of a coolant liquid is recommended, especially for all close tolerance operations.
Spark producing operations in particular must not be run dry, since smoldering fires might result. Where a recirculating system is not available, best results will be obtained with air-powered spray or mist equipment. Use of tapped metal inserts should be considered where electrical performance will not be degraded. Inserts may be cast in place, or bonded with castable material of suitable composition.