Bal-tec™ Home Spherical Location Device
An excellent spherical contact (Part #40070) is produced by using a hardened stainless steel ball with a #10-32 threaded hole in it. They are usually sold in sets of six pieces (Part #40080). When one of these 3/4 inch ( 0.75", 1.9 cm) diameter balls is screwed down into the standard one half inch (1.27 cm) diameter counter-bore in a Location Device Positioner, you get a very accurate and extremely rigid location point.