Bal-tec™ Home Diamond Kinematic Spheres
When the very ultimate in repeatability is required, spherical diamond kinematic components are the answer. We have measured repeatability of a high quality sphere in a three diamond kinematic coupling at less than one half of a microinch (12.5 nanometers). Depending on whose research you read, natural diamond has a stiffness or Young's Modulus of Elasticity somewhere around 900,000,000 P.S.I., which makes it by far the most rigid substance available.
In order to provide the very rigid structural loop required for nanometer (submicroinch) resolution, a one eighth of a carat gem quality diamond is brazed into a tungsten carbide substrata. This T.C. disk is three eighths of an inch (9.5mm) diameter by one quarter of an inch (6.4mm) thick. It is recessed on the backside to leave an annular ring around the edge. This annular ring is lapped flat within one light band. There is a #10-24 threaded hole in the center of the backside to hold this disk rigidly on the Kinematic Platform. The diamond is ground and polished to a rather large three sixteenth of an inch (4.8mm) spherical radius, which is equivalent to a three eighths of an inch (9.5mm) diameter ball.
One form of kinematic system to utilize these devices is three tungsten carbide cylinders and six of the spherical diamonds. Another configuration has one tungsten carbide ball, one tungsten carbide cylinder and one of the spherical diamonds on one of the platforms. The other platform has a three-diamond nest to mate with the T.C. ball, a two-diamond cradle to locate the T.C. cylinder and a flat T.C. disk to mate with the spherical diamond. Glue these components into counterbores for best results.
The price of these components is in the $300 range, depending on the current diamond market.