Kemmler HKS High Performance Milling Chucks

Available Sizes and Part Numbers

Full range of sizes: see manufacturer catalog.

Purpose and Application

Kemmler HKS system power milling chucks are designed for installation on CNC milling machines and machining centers with SK spindles according to ISO 7388-1 (formerly DIN 69871). The chucks are specifically engineered for heavy-duty power milling (Schwerzerspanung) with large cutting depth and width, where enhanced radial rigidity and maximum torque transmission are required to prevent tool pull-out.

Design and Features

A key structural feature of HKS chucks is the increased body mass and rigidity, providing stability under high radial loads. Tool clamping begins just 3 mm from the chuck face, ensuring high positioning accuracy and minimal radial runout (≤ 3 µm). Extreme clamping torque (up to 2000 Nm for HKS 25 and HKS 32 sizes) prevents shank slipping or pull-out during heavy operations. Factory dynamic balancing is executed to class G 6.3 at 15,000 rpm. The chucks are equipped with a bore for an RFID chip.

Compatibility

Chucks are compatible with machine spindles featuring SK 40 and SK 50 tapers (ISO 7388-1 / DIN 69871). They are intended for direct clamping of cylindrical shank tools conforming to DIN 1835 Form A, B, E and DIN 6535 Form HB, HE of corresponding nominal diameters (20 mm, 25 mm, 32 mm). Special HKS series reduction sleeves are used to clamp smaller shank diameters (from 3 mm). Spindle mounting is performed using pull studs according to ISO 7388-3 (formerly DIN 69872).

Selection Parameters

Selection is based on spindle taper size (SK 40 or SK 50) and required HKS bore diameter:

• HKS 20: direct 20 mm shank clamping (3–16 mm with sleeves), clamping torque 780 Nm, projection LPR = 90 mm, body diameter BD = 53 mm;
• HKS 25: direct 25 mm shank clamping (3–20 mm with sleeves), clamping torque 2000 Nm, projection LPR = 105 mm (SK40) / 90 mm (SK50), body diameter BD = 63 mm;
• HKS 32: direct 32 mm shank clamping (3–25 mm with sleeves), clamping torque 2000 Nm, projection LPR = 105 mm (SK40) / 90 mm (SK50), body diameter BD = 68 mm.

Coolant supply is implemented in Form AD/B execution (universal supply through center or flange).

Key Advantages

• Extreme Clamping Force: holding torque up to 2000 Nm eliminates cutter pull-out under heavy loads.
• Enhanced Radial Rigidity: massive body dampens vibrations and improves machined surface quality.
• Precision and Tool Life Preservation: radial runout ≤ 3 µm extends cutting tool longevity.
• Face Clamping: effective clamping begins just 3 mm from the front face plane.
• Diameter Flexibility: use of HKS reduction sleeves allows clamping tools with shanks from 3 mm.