Bal-tec™ Home Cylinderized Gage Balls
In some cases, there are obstructions built into the parts to be tested that would prevent a completely spherical ball from reaching the surface to be evaluated. Grinding a cylindrical stripe of reduced diameter on the outside diameter of the ball will provide the required clearance that will allow access to the spherical surfaces of interest.
A complete ball can have a cylindrical stripe ground on it as shown in Figure #1, or a ball on a stem or handle can have the cylinder ground on it, as shown in Figure #2.