Thread mounted balls are an excellent method for mounting high quality spheres for kinematic couplings and optical table bread boarding.
The contact spheres are made from a very high quality Martinsetic stainless steel balls that are hardened to 58 HRC minimum. This ultra fine grained material has a very high tensile strength of 285,000 psi.
In order to keep a low profile, these contact balls are truncated to form a hemisphere.
This hemisphere is epoxy glued over a pin into a shallow counterbore in the top of a hex head bolt. The thread of this bolt is a 1/4 inch (slightly over 6mm) diameter with 20 threads per inch.
This mounting method provides extremely high shear strength, to the assembly. The shear strength of the balls is as strong as the bolt itself.
The one quarter inch twenty mounting thread, is three hundred thousandths of an inch (0.300”) [7.62mm] long ( ¼-20 X 0.300” ) .
The head of the hexigonical shape body of these devices is one quarter of an inch (0.250”) [6.15mm] thick.
The bodies are black oxide coated to provide corrosion resistance.
This part has a one half inch (0.500”) [25.4mm] hexigonical head.