A complete ER collet chuck system now spans six standard sizes from ER11 through ER40, conforming to DIN 6499 taper geometry. DIN 6499 (internationally standardized as ISO 15488) defines the 8° collet setting angle, taper geometry, and clamping dimensions that make ER collets universally interchangeable across holders from any manufacturer. The range provides a unified tool-holding solution for applications from micro-machining through heavy-duty milling, with precision-grade collets achieving radial runout of ≤0.005mm — meeting the manufacturer UP/AA grade that exceeds ISO 15488 Class 1 requirements.
Complete Size Range
The lineup covers the full spectrum of clamping requirements defined by the ER standard.
| Series | Clamping Range | Typical Applications |
|---|---|---|
| ER11 | 0.5-7mm | Micro-machining, engraving, electronics |
| ER16 | 1-10mm | Light milling, drilling, small parts |
| ER20 | 1-13mm | General purpose machining |
| ER25 | 2-16mm | Medium-duty milling and drilling |
| ER32 | 2-20mm | Heavy milling, large diameter tools |
| ER40 | 3-26mm | Heavy-duty roughing, large boring bars |
Each chuck is precision-ground from hardened alloy steel with a DIN 6499 standard taper for universal compatibility with existing ER collets from any manufacturer. DIN 6499 is required for universal ER collet interchangeability because it standardizes the 8° half-angle taper, collet bore diameters, and nut thread dimensions; collets and chucks from different manufacturers are interchangeable within the same nominal size class.
For first-time CNC users picking ER sizes against typical end-mill and drill shanks, see the CNC tooling setup beginner guide.
Precision Performance
ISO 15488 defines two runout classes for ER collets: Class 2 (normal production grade, ≤0.015mm for d₁ ≤10mm) and Class 1 (tighter tolerance, ≤0.010mm for d₁ ≤10mm); manufacturer UP/AA grades achieve ≤0.005mm TIR, exceeding Class 1 and meeting aerospace and medical device workholding requirements. The precision-grade collets in this range deliver ≤0.005mm runout; standard-grade units conform to ISO 15488 Class 2. Repeatability within 0.002mm ensures consistent part quality across tool changes without re-indicating.
The G2.5 balance grade at 25,000 RPM is preferred for high-speed machining centers because it limits residual imbalance to a level that helps keep spindle bearing loads within the manufacturer's rated dynamic load for typical tool masses and overhangs. Balanced assemblies reduce spindle bearing wear and extend machine tool service intervals.
Applications
Milling -- High clamping force and precision runout enable aggressive material removal while maintaining surface finish requirements. ER32 and ER40 are used for heavy roughing because their clamping force range of 10,000-25,000 N (depending on applied torque) handles large-diameter tools up to 26mm shank diameter without setscrew indentation damage.
Drilling and Reaming -- Concentricity ensures hole straightness and position accuracy, reducing secondary operations. ER20 and ER25 cover the majority of hole-making tool diameters. ER20 and ER25 cover the majority of hole-making diameters from 1mm to 16mm, making them the default starting point for drilling and reaming on general-purpose CNC machining centers.
High-Speed Machining -- Balanced assemblies and secure clamping support spindle speeds up to 30,000 RPM. ER16 and ER20 are preferred for high-speed finishing with small-diameter tools because the smaller collet body mass reduces the centrifugal imbalance contribution at speeds above 20,000 RPM.
Tool Consolidation -- A single chuck system across multiple sizes simplifies inventory management and reduces setup complexity for shops running varied work.
For where ER collet chucks fit alongside drill chucks, hydraulic, and shrink-fit holders in a complete system view, see the tool holding complete guide.
Full ER Range Now Available
Six ER collet chuck sizes (ER11 through ER40) span clamping ranges from 0.5mm to 26mm, with precision-grade collets achieving ≤0.005mm TIR runout, G2.5 balance at 25,000 RPM, and DIN 6499-compliant taper geometry for universal compatibility. The system covers micro-machining through heavy roughing from a single product family.
