This study was performed to examine a method of clarifying the net output of high-speed or light duty spindles that is generally difficult to measure using conventional methods.To determine the relationship between windage(air friction) loss and rotational speed, a disc was attached to an electric motor-driven aerostatic bearing spindle with very low bearing friction loss. The windage(air friction) loss was calculated from the electric input currency and the voltage. The measured windage (air friction)loss was comparable to the theoretically calculated loss with hydrodynamics. Using the disc the windage(air friction) loss of which was clarified, it was possible to determine the net output of spindles, such as air turbine-driven or large bearing loss spindles.

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Shrinkage deformation based on the upsetting mechanism can be generated by laser irradiation of the pipe periphery. Here, step forming based on shrinkage deformation was performed. CO₂ laser beams with a beam diameter of about 1.7 mm, laser power of 400 W, duty factor (DF) of 50%, and traveling speed of 1.0 m/min were applied to 304 grade stainless steel pipe with a diameter of 25 mm and wall thickness of 0.5 mm. When the laser beam was irradiated along a length of 20 mm from 5 mm inside the edge in the direction of the axis around the periphery of the pipe, step-like deformation can be generated over a length of 10 mm in the center portion. The diameter shrinkage was about 0.85 mm, and its ratio to the base material outer diameter was about 3%. Furthermore, correction of the partial roundness of a pipe with a wall thickness of 1 mm was attempted. The laser was used to irradiate the pipes along a straight line axially with DF=25%, v=1.6 m/min at the convex location. When the irradiation was repeated 4 times, the roundness of 29μm was improved to 10μm.

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The breakage resistance of ultra-small-diameter cutting tools must be improved to extend tool life because such tools can be easily broken during machining. One method to improve breakage resistance is to optimize tool shape. However, there have been few reports of such studies for ultra-small-diameter tools. Therefore, we attempted to extend the tool life of ultra-small-diameter gun barrel drills by optimizing the shapes of their cutting parts. Tool life was examined using cemented carbide drills 15μm in diameter fabricated by electrical discharge machining. The results indicated that the tool life could be extended by changing the cutting part cross-section from a semicircle to a quadrant when the semicircular cross-section part was short. Reducing the wedge angle to less than 90°also extended the tool life.

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