Description Calibration/Testing Bars can easily pinpoint any spindle runout and are recommended to be used after any machine “crash” that results in a jolting or forced movement of the spindle, after initial installation of the machine, and also after the machine has been moved/relocated. Test calibration bars are available in HSK-A, HSK-E, HSK-F and ISO or BT versions and manufactured lengths according to customer need.  Concentricity deviation is 0.003mm (0.0001″). We also offer a rental program to verify spindle accuracy periodically and insure machinery is in best condition! GDP Industrial Tooling’s test bars are Made in Germany to the highest quality standards and specifications.