Collet Chart
ER and OZ collets, plus 5C, R8, Morse taper draw-in and Clarkson / Autolock screwed-shank collets, with line drawings.
Download PDF (3 pages, A4)Shop collets and chucks
Nominal dimensions for identifying collets - check against your machine. Drawings not to scale.
ER collets (DIN 6499 / ISO 15488)
| Collet | Clamping range mm | Collet OD mm | Length mm | Nut thread | Set steps mm |
|---|---|---|---|---|---|
| ER8 | 0.5 - 5 | 8.5 | 13.5 | M12 x 0.75 | 0.5 |
| ER11 | 0.5 - 7 | 11.5 | 18 | M14 x 0.75 | 0.5 |
| ER16 | 0.5 - 10 | 17 | 27.5 | M22 x 1.5 | 0.5 / 1 |
| ER20 | 1 - 13 | 21 | 31.5 | M25 x 1.5 | 1 |
| ER25 | 1 - 16 | 26 | 34 | M32 x 1.5 | 1 |
| ER32 | 2 - 20 | 33 | 40 | M40 x 1.5 | 1 |
| ER40 | 3 - 26 | 41 | 46 | M50 x 1.5 | 1 |
| ER50 | 6 - 34 | 52 | 60 | M64 x 2 | 2 |
The number is roughly the collet OD in mm. Each collet grips from its marked size down by its collapse range (about 0.5 mm on ER8 / ER11, 1 mm on ER20 to ER40), so a set in 1 mm steps covers every size in between. Clip the collet into the nut before screwing the nut onto the holder. The nut thread identifies the holder, e.g. ER32 = M40 x 1.5.
OZ collets (DIN 6388) - also sold as HK or EOC
| Series | Holds up to mm | Collet D mm | Length mm | Nut thread | Nut OD mm | Form A | Form B |
|---|---|---|---|---|---|---|---|
| OZ8 (EOC8) | 8 | 14.4 | 26 | M20 x 1.5 | 26 | 401E | - |
| OZ16 (EOC16) | 16 | 24 | 43 | M33 x 1.5 | 43 | 410E | yes |
| OZ20 (EOC20) | 20 | 29.8 | 45 | M42 x 2 | 50 | - | 4541E |
| OZ25 (EOC25) | 25 | 35 | 52 | M48 x 2 | 60 | 444E | 462E |
| OZ32 (EOC32) | 32 | 43.7 | 60 | M60 x 2.5 | 72 | 450E | 467E |
OZ collets have a single 8 deg taper and are pushed into the chuck by a nut bearing on the front face - no drawbar. Form A is slotted from one end and grips close to its marked size (about 0.5 mm); Form B is slotted from both ends. Nut threads are set by the chuck standard (DIN 6391), e.g. OZ25 = M48 x 2, OZ32 = M60 x 2.5. OZ25 is also sold as EOC25 / SYOZ25 (444E / 462E).
Draw-in and threaded collets
| Type | Capacity | Body | Thread / fixing | Used on |
|---|---|---|---|---|
| 5C | Round to 1.1/16" (27 mm); also hex and square | 1.250" body, 10 deg half-angle | 1.238"-20 external, pulled by a draw tube | Lathe spindles, collet blocks, indexers |
| R8 | Round to 3/4" (20 mm) | 0.9495" body, 16 deg 51 min included | 7/16"-20 UNF drawbar, keyway in body | Bridgeport-type milling machines |
| MT2 draw-in | Round to 1/2" (12 mm) | Morse taper 2 body | Internal drawbar thread - 3/8"-16 UNC or M10 (by machine) | Small lathes and mills |
| MT3 draw-in | Round to 5/8" (16 mm) | Morse taper 3 body | Internal drawbar thread - 1/2"-12 BSW, 1/2"-13 UNC or M12 (by machine) | Lathes, mills |
| Clarkson / Autolock | 6, 8, 10, 12, 16, 20, 25 mm; 1/4" - 1" | Nose cone closed by the chuck cap; two drive lugs (wings) at the back | Holds screwed-shank cutters: 20 TPI Whitworth-form thread (BS 122 / DIN 1835 Form D) | Older mills - end mills with threaded shanks |
Draw-in collets are pulled into the spindle by a drawbar or draw tube - the thread must match the machine. Morse taper collets were made with metric, UNC and Whitworth drawbar threads, so check the old drawbar before ordering. Clarkson / Autolock collets are driven by two lugs (wings) at the back and hold end mills with 20 TPI screwed shanks; plain parallel shanks need an ER or side-lock holder.