Producing one of a kind or small quantities of spherical gage tips by conventional machining is a difficult and expensive proposition. Setting up a machine to produce a high quality tiny thread against a shoulder is challenging.

It is desirable to have the thread made of a hard stiff material, but machining such a material straight, concentric, and with a good thread forms in a tiny #4-40 or #2-56 thread is an expensive proposition. The solution is simple, and it's inexpensive. By drilling a small concentric hole in a hard steel or tungsten carbide ball by Electrical Discharge Machining ( EDM) and gluing in a length of high quality rolled threaded stock, the problem is solved.

To further enhance the design, a precision nut is added on the top of the ball. If required, a cylindrical spacer can be inserted between the top of the ball and the nut. The design is quite rugged, as the epoxy glue used in the assembly is a ceramic filled material, with a shear strength of 3000 pounds per square inch.