ER8 collet ER series

SKER

Overview
Our precision clamping collets are designed for secure tool holding in machining applications. With radial run-out lower than competing solutions, these collets minimise deformation and deliver stable accuracy, low wear and extended service life—suited for series production and high-precision operations.

Key features

• Minimal radial run-out for high concentricity
• Low-wear design to maximise tool life
• Wide range of collet types and sizes covering most machining needs

Collet types and ranges (table)
Collet Type | Collet Range | Available precision grades | Precision code | Radial run-out [µm] | Tool clamping dia [mm]
ER | ER 8 - ER 40 | Instrument / Ultra precision / Precision / Standard | PP / P / AA / A | ≤ 1 / ≤ 2 / ≤ 5 / ≤ 8 | 1.0 - 26.0 (PP / P), 1.0 - 26.0 (P), 2.0 - 30.0 (AA / A)
SK | SK 6 - SK 25 | Instrument / Ultra precision / Precision / Standard | PP / P / AA / A | ≤ 1 / ≤ 2 / ≤ 5 / ≤ 8 | 1.0 - 26.0 (PP / P), 1.0 - 26.0 (P), 2.0 - 30.0 (AA / A)
KR | KR 11 - KR 36 | Instrument / Ultra precision / Precision / Standard | PP / P / AA / A | ≤ 1 / ≤ 2 / ≤ 5 / ≤ 8 | 2.0 - 24.0 (PP / P / AA / A)
Clamping Nuts, Blind rivets, Wrenches | (accessories) | (—) | (—) | (—) | (—)

Technical specifications

• ER collets: range ER 8 – ER 40; precision grades: Instrument (PP) radial run-out ≤ 1 µm; Ultra precision (P) ≤ 2 µm; Precision (AA) ≤ 5 µm; Standard (A) ≤ 8 µm; tool clamping diameters from 1.0 mm up to 30.0 mm depending on grade.
• SK collets: range SK 6 – SK 25; same precision grading and radial run-out values; tool clamping diameters from 1.0 mm up to 30.0 mm depending on grade.
• KR collets: range KR 11 – KR 36; same precision grading and radial run-out values; typical tool clamping diameters 2.0 mm – 24.0 mm depending on grade.
• Design priorities: minimise radial run-out, reduce deformation, ensure repeatable accuracy, lower wear and extend service life while optimising cost-efficiency for production environments.
• Available accessories: clamping nuts, blind rivets and wrenches. Accessories are documented separately.