This device adds a new level of accuracy and flexibility to the evaluation of Coordinate Measuring Machines. The Archival Ball Bar (Dumbbell) substantially exceeds the accuracy requirements of the ANSI B89.4.1-1997 for the "Performance Evaluation of Coordinate Measuring Machines”.

This device consists of two ultra precise spheres that are securely mounted in spherical seats at the end of a rather long rigid bar. The contact end of the ultra precise spheres mate with very precisely machined female spherical cups in each end of the bar. This design makes the Archival Ball Bar (Dumbbell) a true three dimensional gage block. The sphere center to center dimension is always very accurately calibrated. This calibration is made traceable to The National Institute for Standards and Technology, and through them to the International Standard of Length.

The material for the bar of this device is a special alloy metal that is heat treated for very long term dimensional stability. All of the metal used for construction of the Archival Ball Bar (Dumbbell) has a normal thermal coefficient of expansion of 6.2 microinches per inch per degree Fahrenheit or 11.4 micrometers per meter per degree Celsius. This makes them compatible with all steel and iron products.