Kemmler 4.5° Shrink Fit Chucks

Available Sizes and Part Numbers

Purpose and Application

Kemmler 4.5° shrink fit chucks are used on CNC milling machines and high-speed machining centers with SK spindles conforming to ISO 7388-1 (formerly DIN 69871). They are designed for clamping solid carbide (HM) and high-speed steel (HSS) tools. The chucks are ideal for high-speed machining (HSC), finishing, and heavy-duty milling operations, delivering maximum torque transmission and long cutting edge tool life.

Design and Features

The operational principle is based on the thermal expansion of the body material when heated by an induction, contact, or hot-air device. Upon cooling, the chuck uniformly and solidly clamps the tool shank with a force significantly higher than mechanical collet chucks. The 4.5° outer taper angle optimizes mounting rigidity and front-end dimensions. Internal radial runout is ≤ 3 µm, and dynamic balancing meets class G 2.5 at 25,000 rpm. The chucks feature an adjustment screw and an RFID chip bore.

Compatibility

The chucks are designed for machine spindles with SK 30, SK 40, and SK 50 tapers (ISO 7388-1 / DIN 69871). Compatible with carbide shanks with h4 tolerance (for 3, 4, 5 mm diameters) and carbide/HSS shanks with h6 tolerance (for 6–32 mm diameters). Spindle retention is achieved via ISO 7388-3 pull studs (formerly DIN 69872). Tool change requires an induction shrink fit unit.

Selection Parameters

Selection is based on SK spindle taper (30, 40, 50) and tool shank diameter (from 3 to 32 mm):

• Standard Versions: projection LPR = 80–100 mm;
• Extended Modifications: projection LPR = 120, 160, 200 mm for deep cavity machining.

Key Advantages

• Solid Clamping Rigidity: uniform clamping across the entire bore surface guarantees resistance to extreme radial forces.
• Precision Accuracy: radial runout ≤ 3 µm extends tool life and improves surface finish.
• Ideal Balancing: class G 2.5 at 25,000 rpm reduces vibration load on the spindle.
• Minimal Contour Interference: compact 4.5° design provides easy access to hard-to-reach workpiece features.
• Fast Tool Change: heating/cooling process takes just seconds when using a shrink fit unit.