What This ER20 Collet Set Delivers in Hard Numbers This is a complete set of CNC machined ER20 spring collets in assorted sizes (1 mm to 20 mm in 0.5 mm and 1 mm steps) for CNC milling and turning c
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What This ER20 Collet Set Delivers in Hard Numbers This is a complete set of CNC machined ER20 spring collets in assorted sizes (1 mm to 20 mm in 0.5 mm and 1 mm steps) for CNC milling and turning c
This is a complete set of CNC machined ER20 spring collets in assorted sizes (1 mm to 20 mm in 0.5 mm and 1 mm steps) for CNC milling and turning centers. Each collet holds tool shanks with a guaranteed runout of ≤0.005 mm at 3×D from the nose, and the slit body is hardened to HRC 58-60 for repeated clamping cycles. We ship standard sets within 7 days from our Dongguan factory, and because we machine in-house, you get this precision without paying a premium for brand names.
The ER20 system uses a tapered outer cone (8° included angle) that compresses radially when the nut is torqued. Our collets are ground after heat treatment, not before, which removes distortion and keeps the gripping bore concentric to the taper. The result: a tool change repeatability of ±0.002 mm, so you don’t need to re-indicate tools after every swap. Slots are wire-cut, not milled, to avoid burrs that push a tool off-center.
We start with 65Mn spring steel or 9Cr18 stainless (for coolant-heavy jobs), not cheap 45# steel. After CNC machining the bore and taper, we vacuum harden to HRC 58-60, then deep-freeze at -80°C for 2 hours to stabilize the structure. This prevents the collet from relaxing its grip after hours of heavy milling. Each collet is then ID ground on a CNC internal grinder to a surface finish of Ra 0.4 µm on the bore, and Ra 0.2 µm on the taper—so it seats cleanly in your ER chuck nut.
Our standard set includes 24 pieces: 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, 8, 9, 10, 11, 12, 13, 14, 15, 16, 18, 20 mm. Each collet is laser-marked on the flat face with its size and a batch code—no guessing which one is in your hand when you’re up against a spindle. We also make custom bore sizes (e.g., 5.8 mm for reamers, 6.35 mm for 1/4") on request, with the same tolerance and hardness. All collets are cleaned and anti-rust oiled before packing in a blow-molded case with a size chart.
| Specification | Value |
|---|---|
| Collet Type | ER20 spring collet, DIN 6499 compliant |
| Sizes Included | 1–20 mm (24 pieces, assorted) |
| Material | 65Mn spring steel or 9Cr18 stainless (optional) |
| Hardness | HRC 58-60 (after vacuum heat treatment) |
| Runout (TIR) | ≤0.005 mm at 3×D from collet nose |
| Bore Surface Finish | Ra 0.4 µm (ID ground) |
| Taper Surface Finish | Ra 0.2 µm (OD ground) |
| Clamping Range per Collet | 1 mm (e.g., 6 mm collet grips 6.0–7.0 mm) |
| Lead Time | 7 days for standard set, 15 days for custom sizes |
| MOQ | No MOQ—order 1 set or 1,000 pieces |
Every collet in your set is checked individually, not sampled. We measure runout on a custom mandrel with a 0.001 mm dial indicator, test the taper with a blueing contact check against a master ER20 chuck, and verify hardness on a Rockwell tester on the nose face. We also do a 100% dimensional pass on the bore diameter using an air gauge (resolution 0.0005 mm). If any collet fails, it goes to scrap, not to your box. A signed inspection report with batch numbers is included free with every order.
Buying a full set from a single source means you get consistent taper angles and bore concentricity across all sizes—mix-and-match sets from different suppliers often have taper mismatch that causes runout spikes. Our collets are all machined on the same CNC lathe and ground on the same ID grinder in one batch, so the taper angle stays within ±0.5 arc-minutes from collet to collet. That consistency is what lets you trust your tool changes without re-measuring. Plus, because we’re a precision manufacturing factory in Dongguan (20 years, CNC machining + stamping + springs + heat sinks), you can bundle collets with other parts in the same shipment to save freight.
ER20 collets have a 1 mm clamping range. For a 6 mm end mill, you use a 6 mm collet (grips 6.0–7.0 mm). For a 6.35 mm (1/4") shank, you need a 6.5 mm collet (grips 6.5–7.5 mm)—never force a 6 mm collet over a 6.35 mm shank, because that over-elastic deformation creates permanent set and runout. Our set covers all standard metric and imperial sizes in the 1–20 mm range, so you’re covered for most CNC milling jobs. If you need an odd size, we can machine it in 15 days with no extra setup fee for quantities above 10 pieces. For deeper guidance on matching collets to your cutting tools, see our CNC cutting tool selection guide—it covers shank tolerances and collet grip force in detail.
No MOQ—you can order a single 24-piece set or 500 pieces, and the unit price stays the same because we run these on CNC lathes with quick changeover.
Yes, we machine custom bore diameters (like 5.8 mm or 12.7 mm) and offer 9Cr18 stainless for corrosion resistance, with the same HRC 58-60 hardness and 0.005 mm runout guarantee.
We inspect 100% of collets—runout on a mandrel, taper contact with blueing, and bore diameter via air gauge—and include an individual inspection report with your shipment.
Standard assorted sets ship in 7 days; custom sizes or stainless versions take 15 days, and we can express ship via DHL or FedEx from Dongguan.
For our standard ER20 collet set, you don’t need a drawing—just tell me the sizes and quantity. For custom bores or materials, send a simple sketch or note. We’ll reply with a firm price, lead time, and shipping cost within 12 hours (usually faster during China business hours). Email me at sc@bquq.com or WhatsApp +86 13713157787. If you’re also working on a new part, send your drawing for a CNC machining quote at the same time—we’ll combine shipping. And before you finalize your tolerances, check our CNC machining tolerances guide to see what’s achievable without driving up cost. All our collets are made in China, with full traceability from raw material to final inspection.
| Parameter | Capability |
|---|---|
| Materials | AL6061/7075, SUS303/304/316, 45# steel, T2 copper, H59 brass, POM, PEEK, nylon |
| Tolerance | ±0.005mm standard, ±0.003mm on request |
| Machines | 3/4/5-axis CNC, turn-mill, Swiss lathe |
| Surface | Anodizing, nickel, zinc, passivation, sandblast, polish |
| Size Range | Max 400 x 300 x 200 mm |
| Prototype | 72 hours, no MOQ on samples |
| Inspection | Full report per batch, CMM data on request |
