HSK is a hollow, short taper that seats on both the taper and the spindle face simultaneously (dual contact), giving very high rigidity and repeatability at high RPM. It is favored for high-speed machining and 5-axis work where a conventional steep taper would lose grip from centrifugal expansion.
Common forms include HSK-A (general, with coolant) and HSK-E/F (high-speed, symmetric). Sizes are given by the flange diameter — HSK-A63 and A100 are typical on machining centers.
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