HSK or Hollow Shank Adaptors have a short shank and a shallow taper of 1 : 10 as compared to 7 : 24 ratio of a BT adaptor. The HSK holders were designed to facilitate high speed machining without compromising the quality.
The machine spindle envelopes the taper shank of the adaptor while the drawbar along with the collet sleeve is pushed inside the hollow shank. As the drawbar retracts, the collet fingers are pushed against the inner surface of the adaptor thus engaging it with the drawbar.
The steep tapers are mounted onto machine spindles with the help of retention knobs or pull studs. The collet fingers wrap around these retention knobs screwed into the adaptors. As the spindle's speed increase the centrifugal forces acting on the spindle and the collet causes them to expand. The shank of the adaptor being stiff expands at a lower rate. The constant pull from the drawbar causes the adaptor to sink deeper into the spindle, causing a shift along the Z axis and hampering accuracy of the part.
In case of HSK adaptors however the expansion of the collet causes the fingers to further push into the adaptor thus increasing the clamping forces.The thin and flexible walls of the adaptors are subjected to thermal expansion at higher rates than the spindle leading to a firm contact between the two. Furthermore the flange contact of the adaptor with the machine's spindle prohibits any axial movement thus maintaing accuracy even at high RPMs.
Akros HSK Adaptors come pre-balanced at G6.3@20000RPM, fine balacing of G2.5@25000RPM is available on request.
Combi Shell arbours are used for cutters with keyways or driving slots. Akros Adaptors have a standard balancing of G6.3@15000 RPM; Finer balancing on request.
HSK Collet chucks are used with collets to hold a range of cylindrical shanks. Akros HSK adaptors come pre-balanced at G6.3@20000 RPM; Finer balancing on request
HSK Side Lock Adaptors are used to clamp tools with straight or weldon shanks. Akros HSK adaptors come pre-balanced at G6.3@20000 RPM; Finer balancing on request