An ER collet size chart helps you match the collet’s outside dimensions to its ER series, then choose an individual bore range that includes your tool shank. Start with the series specified for your holder; within that series, select a collet whose stated shank range covers the measured diameter.
ER Collet Size Chart: Outside Dimensions
The ER series identifies a collet’s physical size, while the bore range identifies the tool shanks an individual collet can clamp. Techniks lists the following lengths and outside diameters for its replacement collets. These dimensions help identify the series; they don’t tell you the bore size of a particular collet.
| ER series | Length, L | Outside diameter, D |
|---|---|---|
| ER8 | 13 mm (.51″) | 8.5 mm (.33″) |
| ER11 | 18 mm (.708″) | 11.5 mm (.45″) |
| ER16 | 27.5 mm (1.08″) | 17 mm (.67″) |
| ER20 | 31.5 mm (1.24″) | 21 mm (.83″) |
| ER32 | 40 mm (1.57″) | 33 mm (1.3″) |
| ER40 | 46 mm (1.81″) | 41 mm (1.61″) |
| ER50 | 60 mm (2.36″) | 52 mm (2.05″) |
These are Techniks dimensions for the listed replacement-collet family, not wencerl specifications. Use the dimensions as an identification aid, then check the collet maker and part number before ordering.
ER Series and Shank Ranges
An ER series can cover several shank diameters through separate collets. That collective capacity isn’t the amount by which one collet can close.
For example, Techniks lists its ER32 set 04205MS as 18 pieces, with a set range of 3–20 mm in 1 mm steps and a shank-size range of 2–20 mm. Within that series, Techniks lists individual collet 04232-05 for a 4–5 mm shank range and 04232-10 for 9–10 mm. Neither individual collet covers the full set range.
| Techniks individual collet | ER series | Shank range |
|---|---|---|
| 04211-06.0 | ER11 | 5.5–6 mm |
| 04232-05 | ER32 | 4–5 mm |
| 04232-10 | ER32 | 9–10 mm |
| 04250-14 | ER50 | 12–14 mm |
The ranges differ between these individual parts. Don’t assume every ER collet has a 1 mm clamping range: specialized versions and products from different manufacturers may differ.
How to Choose an ER Collet
- Identify the holder’s ER series. Check the holder and nut specifications before choosing a collet. An outside-dimension measurement can help identify an unknown collet, but it doesn’t establish compatibility on its own.
- Measure the tool shank. Use the actual shank diameter to select the bore range, rather than relying only on the tool’s cutting diameter.
- Check the individual part number. Choose a collet whose manufacturer-stated shank range includes the measured diameter. Don’t use a collet for an oversized shank.
- Check the remaining specifications. Confirm the bore tolerance, clamping capability, runout, and compatible nut and holder for the exact collet.
If a shank measures 12.2 mm, a collet rated for 11–12 mm is too small. REGO-FIX gives 11.5–12.5 mm and 12–13 mm collets as examples of ranges that can accommodate that diameter; check the actual part before selecting it.
For a replacement, compare the markings and measurements on your existing collet with the holder requirements. You can also browse our ER collets and check the exact part specifications before ordering.
Collet Selection Before Ordering
Keep the holder series and measured shank diameter together when comparing parts. If you need a holder as well, our machining chuck category is a starting point; verify that the holder, nut and selected collet are compatible.
FAQ
Does ER32 Mean a 32 mm Bore?
No. ER32 identifies the collet series, not the bore diameter. Individual ER32 collets have their own stated shank ranges.
Can One Collet Cover Every Shank Size?
No. A series or set can cover a range using separate collets. Choose an individual collet whose stated range includes your shank diameter.
Is Every ER Collet’s Range 1 mm?
No. The listed Techniks examples include individual ranges of 0.5 mm, 1 mm and 2 mm. Check the exact manufacturer and part number, including for specialized versions.