# ER collets ER8, ER11, ER16, ER20, ER25, ER32, ER40, ER50: collet diameter, length, clamping range and nut thread (DIN 6499 / ISO 15488)

> What are the dimensions of ER11, ER16, ER20, ER25, ER32 and ER40 collets and their nut threads?

- Category: Hardware › Machine tool tapers & collets
- Kind: Standard part
- Basis: cgtk.co.uk (holder-side taper and nut thread), Little Machine Shop and RicoCNC (collet OD, length, clamping range, agree with each other), AIMS Industrial (ER8 / ER50 and maximum shank); numbers only
- Page: https://xemstudio.com/objects/er-collets-er8-er50/ · JSON: https://xemstudio.com/api/geometry?object=er-collets-er8-er50 · Plain text: https://xemstudio.com/objects/er-collets-er8-er50/sheet.txt
- License: dimension sheet CC BY 4.0 (Xem Studio); files CC BY 4.0 or their publisher's license
- Use in every chat: add https://xemstudio.com/mcp as a connector (https://xemstudio.com/use-with-ai/)

**Exact dimensions.** True size, with no tolerance added.

## Notes

- ER collets (DIN 6499, ISO 15488) are slotted spring collets that close in a nut; AIMS gives a nominal 1 mm clamping range for most sizes. The number is the nominal taper size in mm: ER16 sits in a holder whose taper OD is 16 mm (the cgtk column). The collet body itself is slightly larger: 11.5, 17, 21, 26, 33, 41 mm (ER32 is printed as 33 in all three sources that list lengths; one AIMS paragraph says 32), and the lengths are 18, 27.5, 31.5, 34, 40, 46 mm. Little Machine Shop, RicoCNC and AIMS agree on diameter and length for every size.
- Clamping range: Little Machine Shop and RicoCNC print 0.5–7, 0.5–9, 1–13, 1–16, 1–21, 3–26 mm for ER11 to ER40; AIMS prints a maximum shank of 7, 10, 13, 16, 20, 26 mm. The two differ at ER16 (9 / 10) and ER32 (21 / 20); both are shown and not averaged. Check your collet's own marking. The cgtk column 'taper OD / bore / minimum bore length' is the holder side as published there; the nut thread column is its nut thread diameter × pitch and thread length. cgtk notes that some ER sizes have different nut styles, so their thread need not match. ER8 and ER50 are in AIMS' table only.
- Why no files: the collet body is a slotted spring shape whose slot pattern and taper angle are not published as numbers in the sources read; a plain tube would not be a collet. Makers (Kennametal, Hoffmann, Rego-Fix, Schunk) carry 3D data on their own product pages.
- Not here: ER nut dimensions (width across flats, height, bearing-nut styles), collet slot pattern, sealed (ER-GB) collets, ER holders and tool holders per taper (see steep-taper-7-24-cat-bt-nmtb-30-40-50), and runout grades.

## Sizes

| size | collet OD (mm) | collet length (mm) | clamping range (mm), Little Machine Shop / RicoCNC | max shank (mm), AIMS | cgtk: taper OD / bore / min bore length (mm) | nut thread (mm), cgtk | nut thread length (mm) |
|---|---|---|---|---|---|---|---|
| ER8 | 8.5 (AIMS) | 13.6 (AIMS) | — | 5 (AIMS) | — | — | — |
| ER11 | 11.5 | 18 | 0.5 – 7 | 7 | 11 / 8 / 17 | 14 × 0.75 | 8 |
| ER16 | 17 | 27.5 | 0.5 – 9 (LMS, Rico) | 10 (AIMS) | 16 / 11 / 22 | 22 × 1.5 | 12 |
| ER20 | 21 | 31.5 | 1 – 13 | 13 | 20 / 14 / 27 | 25 × 1.5 | 13 |
| ER25 | 26 | 34 | 1 – 16 | 16 | 25 / 18 / 37 | 32 × 1.5 | 13 |
| ER32 | 33 (a 32 appears once in AIMS' text) | 40 | 1 – 21 (LMS, Rico) | 20 (AIMS) | 32 / 24 / 42 | 40 × 1.5 | 15 |
| ER40 | 41 | 46 | 3 – 26 | 26 | 40 / 31 / 47 | 50 × 1.5 | 16 |
| ER50 | 52 (AIMS) | 60 (AIMS) | — | 34 (AIMS) | — | — | — |

## Where the files are

- cgtk.co.uk (A. S. Budden): [ER collet dimensions: taper OD, bore, minimum bore length, nut thread diameter, pitch and length for ER11 to ER40](https://www.cgtk.co.uk/metalwork/data/er) — web — Publisher's page; dimensions are facts
- Little Machine Shop: [ER collet sizes: length, diameter and clamping range, ER-11 to ER-40](https://www.littlemachineshop.com/info/er_collet_sizes.php) — web — Publisher's page; dimensions are facts
- RicoCNC: [ER8 to ER40 collets, DIN 6499: OD, length, clamping range (agrees with Little Machine Shop)](https://ricocnc.com/products/258-ER8-ER11-ER16-ER20-ER25-ER32-ER40-Collet-Chuck-DIN-6499-Spring-Collets.html) — web — Publisher's page; dimensions are facts
- AIMS Industrial: [ER collet guide: ER8 to ER50 major diameter, length and maximum shank capacity](https://aimsindustrial.com.au/blogs/product-guides/er-collet-guide) — web — Publisher's page; dimensions are facts
- Kennametal: [ER standard collets, metric and inch (maker product pages)](https://kennametal.com/hu/en/products/p.er-standard-collets-metric.1025778.html) — web — Maker product page
- Hoffmann Group: [ER collet ER 16 and ER clamping nuts (maker product pages)](https://www.hoffmann-group.com/US/en/hus/p/308901-2) — web — Maker product page

## Questions

**What is the outside diameter of an ER32 collet?**

33 mm (the nominal size is 32; the collet body is 33 mm in the lists read) and 40 mm long.

**What is the nut thread of an ER16 collet nut?**

M22 × 1.5 in the cgtk table.

**What range does an ER20 collet cover?**

1 to 13 mm, each collet closing over about 1 mm.

## Fits with

- [Morse tapers MT0–MT7 and 4-1/2: gauge diameter, small end, taper per foot, plug depth, shank length, tang length + taper plug and ring gauges](https://xemstudio.com/objects/morse-tapers-mt0-mt7/)
- [7:24 tool-holder tapers 30, 40, 50: CAT, BT and NMTB gauge diameter, flange diameter, length and draw bar thread (CAT40, BT40, DIN 2080)](https://xemstudio.com/objects/steep-taper-7-24-cat-bt-nmtb-30-40-50/)
- [Thread size reference: UNC / UNF and ISO metric coarse / fine — major, minor and pitch diameter, tap drill, clearance hole (close, normal, loose)](https://xemstudio.com/objects/thread-reference-tap-drills-clearance/)