HSK (Hohlschaftkegel, or hollow shank taper) is a spindle tool holder standard defined in DIN 69893. Unlike solid-taper systems such as BT or CAT, an HSK holder makes contact with the spindle at both the taper and the face simultaneously, which gives higher rigidity and better repeatability at high spindle speeds. The number — 63 in HSK63A and HSK63F — is the shank/flange diameter in mm.
HSK63A vs HSK63F. HSK63A is the full-featured form: it has drive keys to transmit higher torque and supports through-spindle coolant, and is the form used with automatic tool changers on general CNC machining centres. HSK63F is a simplified form without drive keys, so it transmits less torque — it's used on smaller, higher-speed spindles where the lighter, more compact holder is the priority, such as router-style and small-diameter high-rpm applications.
Both forms share the same 1:10 taper. DIN 69893 sets the dimensional tolerances that keep tool holders interchangeable between compliant spindles and holders regardless of manufacturer.
We also stock HSK spare parts — clamping units, pull studs and related components — for maintaining existing holders.
All held in UK stock, same-day dispatch before 4pm.
