HSK is short for the German words "Hohl Shaft Kegel" or, in English, Hollow Shank Taper.
There are several major differences between "steep taper" toolholders, like NMTB, CAT & BT and HSK.
As machining spindle speeds have increased, BT and CAT tooling systems tend to lose accuracy due to centrifugal forces from running at high RPM. The mouth of the machining center spindle can grow, "bell mouthing". As it grows the BT and CAT tool is under constant drawbar pull, moves up the expanded taper. This causes the Z-axis offset to change. This can also cause the toolholder to stick in the spindle.
The HSK contacts the spindle taper and flange on the spindle face to make a solid union in both the axial and radial planes. In operation, HSK tool holders are resistant to axial movement because the face contact prevents the toolholder from being pulled up into the spindle at high speed.
Cutting tools generally takes higher radial forces because the flange contact and taper contact combine to resist deflection.
Technical Support Blog
At Next Generation Tool we often run into many of the same technical questions from different customers. This section should answer many of your most common questions.
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