Spindle Knowledge

Hollow shank taper interface (HSK)

The HSK mount is used for clamping tools (milling, drilling). Due to its positive characteristics with regard to accuracy and stiffness, the HSK interface per DIN 69893 has found widespread use in the area of machining. In addition, its suitability for high rotational speeds and the possibilities for rapid tool change have lead to supremacy over the SK interface. The hollow shank taper interface achieves its significantly higher radial and axial stiffness, compared with the steep taper interface, through its flatness. In addition, the flexural rigidity of a hollow shank taper is far greater than that of steep tapers or cylindrical shafts of similar size.    Further advantages of the hollow shank taper lie in the highly reproducible axial change accuracy, with values of less than 1µm, as well as the lower mass and the shorter length compared to the steep taper.  The latter simplifies tool-changing and handling processes in particular.
There are 6 different forms (A, B, C, D, E, F) in the standard, each of which have different characteristics, with the width of the flatness as the design distinction.   Forms A, C and E have a narrow flat surface, whilst forms B, D and F have wide flat surfaces. Further differences can be seen in the design of the coolant feed.  With forms B and D, this is implemented via holes on the collar, whilst with the other forms the cooling lubricant is fed centrally to the tool.
Forms C and D are suitable only for manual tool changing. The most widely used form per DIN69893 is form A. [WECK05], [WECK/SCHUBERT], [LEMBKE]