This is a CNC machined ER collet with a hex bore, designed for holding hexagonal tool shanks and workpieces in precision spindles. You get guaranteed concentricity of ≤0.005mm TIR at the nose, a body
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This is a CNC machined ER collet with a hex bore, designed for holding hexagonal tool shanks and workpieces in precision spindles. You get guaranteed concentricity of ≤0.005mm TIR at the nose, a body
This is a CNC machined ER collet with a hex bore, designed for holding hexagonal tool shanks and workpieces in precision spindles. You get guaranteed concentricity of ≤0.005mm TIR at the nose, a body hardness of HRC 58-60, and a surface finish of Ra 0.4 µm. We ship standard sizes in 7-10 days, and custom hex sizes in 12-15 days, direct from our Dongguan factory.
A hex bore locks the tool shank on six flat faces, not a friction fit. This eliminates slippage under high torque loads, which is critical when driving reamers, taps, and end mills with hex shanks. Our hex bore is wire-cut and then CNC ground to achieve a width-across-flats tolerance of +0.005 mm / -0.000 mm. That means the tool seats fully, without rocking, and stays centered even at 10,000 RPM.
We machine our ER collets from two grades. For standard hex bores up to 10mm, we use 9SiCr alloy tool steel. For larger bores and high-wear applications, we use 20CrMnTi carburizing steel. Both are hardened in vacuum furnaces to HRC 58-60, then deep cryogenically treated to -120°C to convert retained austenite. This process yields dimensional stability under repeated clamping cycles—over 50,000 cycles without measurable relaxation.
Runout is killed in the grinding stage, not the machining stage. After CNC milling the bore, we harden the blank. Then we grind the outer diameter to a 0.005mm tolerance. Next, we grind the hex bore using a CNC internal grinder with a diamond dresser. Finally, we grind the taper angle (8° per side) and the clamping slots simultaneously on a jig grinder. This sequence references every critical feature to the same centerline, holding total indicated runout (TIR) to ≤0.005mm at 3x diameter from the nose.
| Specification | Value / Range | Note |
|---|---|---|
| Hex Bore Size (A/F) | 1.5 mm – 12 mm | Custom sizes on request |
| Collet Body OD | ER11, ER16, ER20, ER25, ER32, ER40 | Standard ER series |
| Material | 9SiCr / 20CrMnTi | Case-hardened or through-hardened |
| Hardness (Core) | HRC 58-60 | Vacuum heat treated |
| Hardness (Surface) | HRC 60-62 (case) | Carburized depth 0.3-0.6 mm |
| Total Runout (TIR) | ≤ 0.005 mm | At nose, 3xD |
| Hex Width Tolerance | +0.005 / -0.000 mm | Interference fit on shank |
| Surface Finish (Bore) | Ra 0.4 µm | Ground and honed |
| Concentricity (Bore to OD) | ≤ 0.003 mm | Gage checked |
| Lead Time (Standard) | 7-10 days | Ex-works Dongguan |
| MOQ | No MOQ | Sample orders accepted |
The clamping slots are not milled straight through. We cut them with a 0.3mm wire EDM after grinding, then open the slot mouth to 0.5mm on the front face. This creates a spring effect that allows the collet to close evenly around the hex shank. We control slot depth to within ±0.02mm so that the collet's elasticity range (typically 0.1mm collapse) remains consistent across every part. If a slot is too deep, the collet cracks under clamping force; too shallow, and it won't grip. We verify collapse force on a hydraulic test rig for each production batch.
Every ER collet we ship goes through a 100% inspection, not sampling. We use a Federal air gage to measure hex width and bore taper in three planes. A Zeiss CMM checks runout and concentricity on a 5-point fixture. We also perform a hardness test on a Rockwell tester for every 10th piece. You receive a dimensional report with your shipment—no extra charge. This is part of our precision manufacturing process, not a premium service.
No MOQ. We accept a single piece for custom hex sizes, though the unit price is higher for a one-off due to setup time.
Yes, we can extend the body length up to 25% over standard ER dimensions, but we must re-verify runout after grinding because longer bodies amplify flex.
We use a two-step grinding process (rough and finish) on the OD and bore, and we re-check every part after slot cutting to catch any stress relief distortion.
For standard ER11 and ER16 hex collets, 100 pieces ship in 10 working days. For ER32 and larger, add 3 days for grinding cycles.
We are a precision manufacturing factory in Dongguan, China, with 20 years of experience in CNC machining and tooling. Our ER collet hex bore line is a direct response to engineers who need repeatable clamping for hex-shank tools without paying a premium for European brands. Before you specify a collet, check our CNC cutting tool selection guide to match the collet grade to your spindle speed. Also, review our CNC machining tolerances guide to understand how our 0.005mm runout compares to your application needs.
Send us your drawing or a sketch of your hex shank dimensions. Our engineers will reply with a firm quote within 12 hours, including a suggested material grade. For a quick response, email sc@bquq.com or WhatsApp +86 13713157787. We are ready to machine your first piece today.
| 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 |
