Guide
ER Collet Size Chart: ER8 to ER50 Clamping Ranges, Nuts and Sealing Rings
Every ER size PTP makes, from the DIN 6499 collet tables: the collet diameter, the collets in each size and the range each one clamps, the collet sets, the clamping nuts and the sealing rings for coolant-through tools. Every ordering code links to its own page.
Last updated 29 October 2026
ER collet sizes and clamping ranges
Each collet clamps a small range below its nominal size (for example the ER32 Ø10 collet holds 10.0 to 9.0 mm). The set holds one collet of each size.
| ER size | Collet Ø (D1) | Collets (nominal Ø) | Range per collet | Clamping range | Collet set |
|---|---|---|---|---|---|
| ER8 | 8 mm | 9 (Ø1–5 mm) | 0.5 mm | 0.5–5 mm | 37COER08-0105S09 (9 pcs) |
| ER11 | 11 mm | 13 (Ø1–7 mm) | 0.5 mm | 0.5–7 mm | 37COER11-0107S13 (13 pcs) |
| ER16 | 16 mm | 10 (Ø1–10 mm) | 1 mm | 0.5–10 mm | 37COER16-0110S10 (10 pcs) |
| ER20 | 20 mm | 12 (Ø2–13 mm) | 1 mm | 1–13 mm | 37COER20-0113S13 (13 pcs) |
| ER25 | 25 mm | 15 (Ø2–16 mm) | 1 mm | 1–16 mm | 37COER25-0216S15 (15 pcs) |
| ER32 | 32 mm | 18 (Ø3–20 mm) | 1 mm | 2–20 mm | 37COER32-0320S18 (18 pcs) |
| ER40 | 40 mm | 23 (Ø4–26 mm) | 1 mm | 3–26 mm | 37COER40-0326S19 (19 pcs) |
| ER50 | 50 mm | 12 (Ø12–34 mm) | 2 mm | 10–34 mm | 37COER50-1034S12 (12 pcs) |
Which nut and sealing ring go with each ER size?
Slotted and hex (ER-A) clamping nuts with their thread and outside diameter, the mini ER-M nut code, and the sealing rings for coolant-through tools.
| ER size | Slotted nut | Thread, Ø | Hex nut (ER-A) | Thread, Ø | Mini nut (ER-M) | Sealing rings |
|---|---|---|---|---|---|---|
| ER8 | – | – | – | – | 36CCNER8M | – |
| ER11 | – | – | 36CCNER11A | M14×0.75, Ø19 mm | 36CCNER11M | – |
| ER16 | 36CCNER16 | M22×1.5, Ø32 mm | 36CCNER16A | M22×1.5, Ø28 mm | 36CCNER16M | 5 rings, tool Ø6–10 mm |
| ER20 | 36CCNER20 | M25×1.5, Ø35 mm | 36CCNER20A | M25×1.5, Ø34 mm | 36CCNER20M | 8 rings, tool Ø6–13 mm |
| ER25 | 36CCNER25 | M32×1.5, Ø42 mm | – | – | 36CCNER25M | 11 rings, tool Ø6–16 mm |
| ER32 | 36CCNER32 | M40×1.5, Ø50 mm | – | – | – | 15 rings, tool Ø6–20 mm |
| ER40 | 36CCNER40 | M50×1.5, Ø63 mm | – | – | – | 15 rings, tool Ø6–20 mm |
| ER50 | 36CCNER50 | M64×2, Ø78 mm | – | – | – | – |
What does the number in ER32 mean?
It is the collet size: PTP's DIN 6499 collet table gives a collet diameter (D1) of 32 mm for ER32, 16 mm for ER16 and 50 mm for ER50. A chuck takes only collets of its own ER size.
Which ER size fits which collet chuck?
From the PTP collet chuck tables, by shank size.
| Chuck | ER sizes |
|---|---|
| BT30 ER chucks | ER16, ER20, ER25, ER32 |
| BT40 ER chucks | ER16, ER20, ER25, ER32, ER40, ER50 |
| BT50 ER chucks | ER16, ER20, ER25, ER32, ER40, ER50 |
| SK30 ER chucks | ER16, ER20, ER25, ER32 |
| SK40 ER chucks | ER16, ER20, ER25, ER32, ER40, ER50 |
| SK50 ER chucks | ER16, ER20, ER25, ER32, ER40, ER50 |
| HSK-A50 ER chucks | ER16, ER20, ER25, ER32 |
| HSK-A63 ER chucks | ER16, ER20, ER25, ER32, ER40 |
| HSK-A100 ER chucks | ER16, ER20, ER25, ER32, ER40 |
| BT30 mini ER chucks | ER11M, ER16M, ER20M, ER25M |
| BT40 mini ER chucks | ER11M, ER16M, ER20M, ER25M |
| BT50 mini ER chucks | ER16M, ER20M, ER25M |
| SK30 mini ER chucks | ER11M, ER16M, ER20M, ER25M |
| SK40 mini ER chucks | ER11M, ER16M, ER20M, ER25M |
| SK50 mini ER chucks | ER16M, ER20M, ER25M |
| HSK-A50 mini ER chucks | ER11M, ER16M, ER20M, ER25M |
| HSK-A63 mini ER chucks | ER11M, ER16M, ER20M, ER25M |
| HSK-A100 mini ER chucks | ER16M, ER20M, ER25M |
Sealing ring or sealed nut?
Both are for coolant-through tools. An ER sealing ring sits in a standard ER collet and seals around the tool shank; each ring is made for one shank diameter. A sealed (ERS) collet nut is the alternative for coolant-through tools.
DIN 6499 or ISO 15488?
PTP's ER collets, clamping nuts and sealing rings are made to DIN 6499; its ER collet chucks are listed to DIN 6499 / ISO 15488.
Questions about ER collets
What is the clamping range of an ER32 collet?
ER32 collets cover Ø2–20 mm: 18 collets from Ø3–20 mm, each clamping a 1 mm range (the Ø10 collet holds 10.0 to 9.0 mm). They come singly or as the 18-piece set 37COER32-0320S18.
Which nut fits an ER32 collet chuck?
The ER32 slotted clamping nut 36CCNER32: thread M40×1.5, Ø50 mm.
How do I seal an ER collet for coolant-through tools?
Fit an ER sealing ring in the standard collet: PTP makes them for ER16, ER20, ER25, ER32, ER40, for tool shanks from Ø6 mm. A sealed (ERS) collet nut is the other option.