Collet Standards Chart: 5C, 16C, 2J, ER, R8 and TG
Short answer: The six collet families buyers ask about most are 5C (round bore up to 26 mm / 1.0625 in), 16C (up to 26 mm with a larger body), 2J (up to 27.9 mm / 1.1 in for auto-lathe work), ER (ER8 to ER50, gripping 1–34 mm), R8 (up to 22 mm / 0.875 in on manual mills) and TG (TG75/TG100/TG150, up to 25.4 mm / 1 in). All are spring collets that grip by elastic compression, but they differ in body geometry, drawbar or nut actuation, and TIR. Standard-grade collets typically hold 0.015–0.05 mm TIR; precision grades reach 0.005–0.01 mm. BQUQ manufactures and sources these families in one ISO9001 Dongguan factory and quotes in 12 working hours.
What every collet standard has in common
Every collet in this chart is a slotted, hardened steel sleeve. A taper or nut squeezes the sleeve inward, and the slots let the bore close elastically onto the tool shank or workpiece. The differences are all in the interface:
- Body diameter and taper angle — determines which chuck, spindle or fixture the collet fits.
- Actuation — drawbar pull (5C, 16C, 2J, R8) versus nut compression (ER, TG).
- Gripping range — how far a single collet can collapse before accuracy degrades.
- Accuracy class — stated as TIR at a defined distance from the collet face.
Because the working principle is identical, a shop can standardize on one or two families and still cover most turning, milling and tool-holding work. The mistake is mixing families without checking the interface — a 5C collet will not seat in an ER chuck, and an ER32 nut will not close a TG100 collet.
Why the "standard number" matters more than the brand
The number in the name (5C, 16C, 2J, ER32, R8, TG100) is a dimensional standard, not a brand. A 5C collet from any qualified maker should fit any 5C fixture within the standard's tolerances. When you buy collets, confirm the standard number, the bore size, the accuracy class and the material — those four items define what you actually receive.
Collet standards chart: the six families side by side
The table below summarizes the families in this article. Ranges are typical values for standard product; exact limits vary by maker and bore style.
| Family | Actuation | Typical max round bore | Common shank/interface | Typical TIR (standard grade) | Best-fit application |
|---|---|---|---|---|---|
| 5C | Drawbar, 1.041 in body | 26 mm / 1.0625 in | 5C spindle nose, fixture blocks | 0.015–0.025 mm | Lathe workholding, small mill fixtures |
| 16C | Drawbar, larger body | 26 mm | 16C spindle nose | 0.015–0.025 mm | Higher-grip turning, heavier stock |
| 2J | Drawbar | 27.9 mm / 1.1 in | Auto-lathe collet chucks | 0.02–0.05 mm | Automatic lathes, bar feed |
| ER | Nut compression | ER8: 5 mm → ER50: 34 mm | ER collet chucks, tool holders | 0.01–0.02 mm | End mills, drills, tapping |
| R8 | Drawbar, 7/8 in shank | 22 mm / 0.875 in | R8 mill spindle | 0.02–0.04 mm | Manual mills, bridgeport-type heads |
| TG | Nut compression | TG75: 19 mm → TG150: 25.4 mm | TG collet chucks | 0.01–0.02 mm | High-grip milling, heavy cuts |
5C collets: the default for lathe workholding
5C is the most widely copied collet standard in the world. The body is nominally 1.041 in diameter with a 20° included taper, and it is pulled into the spindle or fixture by a drawbar. Round bores run up to 26 mm (1.0625 in), and the same body is available with hex, square and emergency (unbored) bores.
5C is popular because the interface is simple and the collet is short, which keeps the workpiece close to the spindle bearing. Standard-grade 5C collets typically hold 0.015–0.025 mm TIR; precision-ground versions reach 0.005–0.01 mm. If you need a starting point for bore styles and step collets, our collet catalog selection guide walks through the options.
16C collets: more grip in a bigger body
16C uses the same 20° taper family logic as 5C but with a larger body, so it can take a heavier drawbar pull and resist higher cutting forces. Max round bore is in the same 26 mm region, but the extra body mass improves rigidity on interrupted cuts and heavier turning.
Choose 16C when 5C accuracy is acceptable but 5C rigidity is not — for example, roughing a shaft before finishing, or holding a part that overhangs more than a 5C setup comfortably allows.
2J collets: built for automatic lathes
2J collets are drawbar-actuated and sized for automatic lathe collet chucks, with round bores up to about 27.9 mm (1.1 in). They are common on cam and CNC automatic lathes where the collet closes and opens thousands of times per shift.
Because the collet is cycled constantly, 2J buyers should care about spring fatigue and bore wear as much as initial TIR. Typical standard-grade accuracy is 0.02–0.05 mm, which is normally adequate for bar work where the bar itself has its own tolerance. For Swiss-type machines, the guide bushing and collet must be matched — see our collet system selection article for the full picture.
ER collets: the tool-holding workhorse
ER collets are nut-actuated and cover the widest size range of any family here, from ER8 (about 5 mm max) through ER11, ER16, ER20, ER25, ER32 and ER40 to ER50 (about 34 mm max). Each collet has a nominal collapse range of roughly 1 mm, which is why one ER32 collet set can cover a wide band of shank diameters.
ER collets are double-angle (the nut squeezes both ends), which keeps the tool concentric and allows the collet to be used for both milling and drilling. Standard-grade TIR is typically 0.01–0.02 mm. ER is the family most shops standardize on for tool holding, and it is the family most often specified alongside tool holder collet chucks.
R8 collets: the manual mill standard
R8 is a drawbar collet with a 7/8 in shank and a keyway that indexes in the spindle. Round bores go up to 22 mm (0.875 in). It is the classic manual-mill interface and remains common in job shops and maintenance departments.
R8 accuracy is typically 0.02–0.04 mm, which is fine for manual work but rarely chosen for high-speed CNC milling. The keyway is a wear point — a worn key or spindle slot shows up as repeatability loss, not as a sudden failure.
TG collets: high grip for heavy milling
TG collets (TG75, TG100, TG150) are nut-actuated like ER but with a steeper, shorter taper that produces more gripping force per unit of nut torque. Round bores run to about 25.4 mm (1 in) on TG150.
The trade-off is collapse range: TG collets close over a narrower band than ER, so you need more collets to cover the same shank sizes. In exchange you get better resistance to tool pull-out in heavy milling. Our TG collet guide covers the TG75/TG100/TG150 differences in detail.
Size and range comparison: how much can each collet grip?
Use this table to check whether a single collet can cover the shank or bar you have in mind. Values are typical and indicative; confirm against the maker's data sheet before committing to a process.
| Collet | Nominal collapse range | Round bore steps commonly stocked | Nut or drawbar torque sensitivity |
|---|---|---|---|
| ER8 | ~0.5 mm | 1–5 mm | High — small nut, easy to over-torque |
| ER16 | ~1.0 mm | 1–10 mm | Medium |
| ER20 | ~1.0 mm | 1–13 mm | Medium |
| ER25 | ~1.0 mm | 2–16 mm | Medium |
| ER32 | ~1.0 mm | 2–20 mm | Medium |
| ER40 | ~1.0 mm | 3–26 mm | Medium-high |
| ER50 | ~1.0 mm | 6–34 mm | High |
| 5C | ~0.5 mm (round bore) | 1–26 mm in 0.5 mm steps | Drawbar — set by pull force |
| 16C | ~0.5 mm | 1–26 mm | Drawbar |
| 2J | ~0.5 mm | 1–27.9 mm | Drawbar |
| R8 | ~0.5 mm | 1–22 mm | Drawbar |
| TG100 | ~0.25 mm | 3–25 mm | High |
Reading the range column correctly
A "1 mm collapse range" does not mean you should grip a 19 mm shank in a 20 mm ER32 collet and expect full accuracy. Best practice is to grip within roughly 0.5 mm of nominal for critical work and reserve the full range for non-critical holding. Over-collapsing a collet permanently sets it out of round.
How to choose between these standards
Work through these four questions in order:
1. What does the machine accept? The spindle nose or chuck interface decides the family. You cannot substitute a 5C for an ER32 without changing the holder.
2. Is the load axial or radial? Turning and bar feed favor drawbar collets (5C, 16C, 2J). Milling and drilling favor nut-actuated collets (ER, TG).
3. How much accuracy do you need? Standard grade is typically 0.015–0.05 mm TIR. If your drawing calls for tighter, specify a precision grade and expect to pay more.
4. How often does the collet cycle? High-cycle automatic lathe work pushes you toward 2J and toward inspecting bore wear on a schedule.
When to specify a precision grade
Precision grades matter when the collet is the dominant error source. On a lathe, collet TIR transfers almost directly into part runout. On a mill, collet TIR adds to holder and spindle error. If your total budget is 0.01 mm, a 0.04 mm collet leaves nothing for anything else.
Bore styles beyond round
Most of these families are available with hex, square and emergency bores, plus step-collet configurations for short parts. Hex and square bores are cut to nominal size and do not collapse, so they hold across the flats rather than by elastic grip. If your part is a hex fitting or a square shank, specify the bore style explicitly — it is not interchangeable with a round bore of the same nominal size.
Manufacturing and sourcing notes for B2B buyers
Collets are deceptively simple parts. The variables that decide whether a shipment performs are material, heat treatment, grinding sequence and slot cutting.
- Material and hardening. Collets are typically made from alloy spring steel, hardened and tempered to a working hardness that balances grip with elastic recovery. A collet that is too hard cracks; too soft and it takes a set.
- Grinding after hardening. The bore and taper must be ground after heat treatment to hold concentricity. Grinding before hardening loses the tolerance.
- Slot cutting. Slots are cut to a controlled width and depth. Uneven slots produce uneven closing and a lobed grip pattern.
- Marking and traceability. Bore size, standard number and accuracy class should be marked and legible for the life of the tool.
At BQUQ, collets and collet chucks are produced across four production lines in one Dongguan factory under ISO9001, alongside CNC machining to ±0.005 mm, metal stamping, custom springs and heat sinks. That single-site setup matters for buyers: collet bodies, nuts and chuck components can be machined, heat treated and inspected without shipping between vendors. We work with flexible MOQ, so a first order can be a trial quantity rather than a container.
For automatic lathe and Swiss-type applications, our auto-lathe collets line covers the drawbar families described above, and power chucks for Swiss machines covers the actuation side. If your application is high-volume bar work, tell us the bar diameter, the machine model and the cycle rate — those three inputs usually determine the collet family in one exchange.
What to include in an RFQ
Send the standard number, bore size and style, accuracy class, quantity and the machine interface. If you do not know the standard number, send a photo of the existing collet next to a ruler and the machine model. BQUQ returns quotes in 12 working hours.
Frequently Asked Questions
Q: What is the difference between 5C and 16C collets?
A: Both are drawbar-actuated with a 20° taper family geometry and similar maximum round bores around 26 mm, but 16C has a larger body. The bigger body accepts higher drawbar pull and resists more cutting force, which suits heavier turning. 5C is shorter and keeps the workpiece closer to the spindle bearing, so it remains the default for lighter, high-accuracy lathe work.
Q: Can I use an ER collet in a 5C fixture?
A: No. ER collets are nut-actuated with a double-angle profile and seat inside an ER collet chuck; 5C collets are drawbar-actuated with a 1.041 in body that pulls into a 5C spindle nose or fixture block. The interfaces are not interchangeable. To move between families you must change the holder, not just the collet.
Q: Which collet standard is most accurate?
A: Accuracy depends on grade, not family. Standard-grade collets in any of these families typically hold 0.015–0.05 mm TIR, while precision grades reach roughly 0.005–0.01 mm. ER and TG tool-holding collets are commonly offered in tighter grades because tool runout directly affects cutter life and surface finish, but a precision 5C can match them.
Q: How much can an ER32 collet collapse?
A: A typical ER32 collet has a nominal collapse range of about 1 mm, so a 20 mm collet can grip roughly 19–20 mm. For critical accuracy, stay within about 0.5 mm of nominal. Repeatedly over-collapsing a collet permanently deforms it and it will no longer hold concentricity even at its nominal size.
Q: What is a 2J collet used for?
A: 2J collets are drawbar-actuated collets sized for automatic lathe collet chucks, with round bores up to about 27.9 mm (1.1 in). They are used on cam and CNC automatic lathes where the collet opens and closes thousands of times per shift. Because of that cycling, bore wear and spring fatigue matter as much as initial accuracy.
Related Resources
- About BQUQ and our Dongguan factory: /about/
- Collet and chuck product range: /auto-lathe-collets/, /tool-holder-collet-chucks/, /power-chucks-swiss/
- Industry trends in precision manufacturing: /industry-dynamics/
- Technical articles and engineering guides: /bquq-blog/
- Frequently asked questions: /faq/
- Case studies: /case/
- Contact the engineering team: /contact/
Authored by the BQUQ Engineering Team. BQUQ (Dongguan) runs CNC machining (±0.005 mm), metal stamping, custom springs, and heat sink production in one ISO9001 factory. Source-direct from Dongguan, China — quote in 12 hours: sc@bquq.com | WhatsApp +86 13713157787 | www.bquq.com
