Kemmler ER Mini Collet Chucks

Available Sizes and Part Numbers

Full range of sizes: see manufacturer catalog.

Purpose and Application

Kemmler ER Mini series collet chucks (DIN 6499 and ISO 15488 standards) are designed for CNC milling machines and machining centers with SK spindles according to ISO 7388-1 (formerly DIN 69871). The main practical purpose of this series is operating under tight geometric constraints where a standard clamping nut creates contour interference. The chucks are used for finishing and semi-finishing milling, drilling, and engraving in molds, dies, and complex housing parts.

Design and Features

The design slims down the standard chuck contour by utilizing a compact clamping nut (Mini nut). The small outer diameter (DLN starting from 16 mm for ER 11 Mini) allows the tool to enter narrow grooves and deep cavities without the risk of collision between the chuck body and the workpiece. All chucks are made of alloyed case-hardened steel with a surface hardness of HRC 60 ± 2. Inner taper radial runout is ≤ 3 µm, and factory dynamic balancing is executed to class G 2.5 at 25,000 rpm. A bore for an RFID chip is provided in the body.

Compatibility

The tooling is designed for machine spindles with SK 30, SK 40, and SK 50 tapers (ISO 7388-1 / DIN 69871). Compatible with ER system collets of corresponding sizes: ER 11 Mini (4008E), ER 16 Mini (426E), ER 20 Mini (428E), and ER 25 Mini (430E) according to ISO 15488 B standard. Spindle mounting is performed using pull studs according to ISO 7388-3 (formerly DIN 69872). A specialized spanner wrench matching the ER Mini contour is required for nut tightening.

Selection Parameters

Model selection is performed by spindle taper type (SK 30, SK 40, SK 50) and ER Mini collet size:

• ER 11 Mini (4008E): clamping diameters 1–7 mm, nut outer diameter DLN = 16 mm;
• ER 16 Mini (426E): clamping diameters 1–10 mm, nut outer diameter DLN = 22 mm;
• ER 20 Mini (428E): clamping diameters 2–13 mm, nut outer diameter DLN = 28 mm;
• ER 25 Mini (430E): clamping diameters 2–16 mm, nut outer diameter DLN = 35 mm.

Chucks are available in Form AD (central coolant supply) and Form AD/B (switchable coolant supply) executions, as well as extended versions with LPR projection up to 160 mm (e.g., 403.02.07.10.2).

Key Advantages

• Minimal External Dimensions: slim clamping nut (from 16 mm) enables machining in tight zones and deep cavities without contour interference.
• High Accuracy: taper radial runout ≤ 3 µm reduces vibration levels and protects the cutting edge from uneven wear.
• Precision Balancing: class G 2.5 at 25,000 rpm guarantees stable operation in high-speed modes.
• Surface Wear Resistance: case-hardened steel with a hardness of HRC 60 ± 2 prevents deformation of the taper and clamping surfaces.
• Extended Modifications: availability of executions with LPR projection up to 160 mm allows solving deep machining tasks for complex molds.