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Please cite this article in press as: Anandan KP, Ozdoganlar OB. A multi-orientation error separation technique for spindle metrology of miniature ultra-high-speed spindles. Precis Eng (2015), http://dx.a b s t r a c t This paper presents a multi-orientation error separation technique to remove the artifact form error from the radial measurements to obtain the radial spindle error motions of miniature ultra-high-speed (UHS) spindles. Unlike the existing approaches, the present technique neither relies on high-accuracy fixtures, nor necessitates measurements from specific orientations of the artifact. Rather, the spindle error motions are measured from a set of arbitrary artifact orientations using laser Doppler vibrometry (LDV). The angle of each artifact-setup orientation with respect to the spindle is determined with high precision through reflectivity measurement of the marks made on both the artifact and the spindle using another LDV. Although the presented approach can be applied by using different sensors (e.g., capacitance probes), we demonstrate the approach using LDVs. With the displacement measurement direction fixed, measurements are conducted from both LDVs for multiple orientations of the artifact. Using the unique implementation scheme developed in this paper, data from these orientations are post-processed to compute the artifact form error and further remove it from the radial motion measurements to obtain the synchronous radial spindle error motions. A thorough experimental evaluation is presented to quantify both the repeatability of the measured artifact form errors as well as the bandwidth of error separation for various number of artifact orientations. The spindle error motions measured from both the sphere and stem portions of a custom fabricated sphere-on-stem artifact mounted on a typical miniature UHS spindle, are seen to be similar in shape and within 5 nm in magnitude across the revolution, thus demonstrating the effectiveness of the technique. Using this technique, spindle error motions at ultra-high speeds up to 150 krpm were successfully quantified. Although the implementation scheme is demonstrated for miniature UHS spindles, it is readily applicable for error separation on macro-scale spindles without the need for any high-precision fixtures and precise setting of angles.