This is a CNC machined SK40 ER32 collet chuck tool holder built for rigid, repeatable tool clamping on machining centers. We machine the body from 20CrMnTi alloy steel, harden it to HRC 58-62, and gri
This is a CNC machined SK40 ER32 collet chuck tool holder built for rigid, repeatable tool clamping on machining centers. We machine the body from 20CrMnTi alloy steel, harden it to HRC 58-62, and grind the taper to a 0.005 mm total indicated runout (TIR) at the nose. Standard lead time is 15 days, and we offer no MOQ for this item, so you can order one piece for a trial or a hundred for production.
ER collet chucks compress a slotted collet around the tool shank, distributing clamping force evenly over a wide contact area. That means you can hold a 20 mm end mill or a 3 mm drill with the same chuck by just swapping the collet. The ER32 system grips tool shanks from 2 mm to 20 mm, covering 90% of standard milling and drilling tools. Compared to shrink fit, the ER system is adjustable and does not need a separate induction heater. Compared to Weldon, there is no set screw pushing the tool off-center, so runout stays low.
Our SK40 ER32 chuck uses a 4-degree taper collet seat, ground after heat treatment. The ground seat ensures the collet collapses uniformly, which reduces vibration and extends tool life. On a 400 mm long test bar, we consistently measure 0.005 mm TIR or better. That number is verified on a Swiss-made coaxial indicator before every unit ships.
The body starts as 20CrMnTi, a case-hardening steel common in precision transmission parts. We machine the SK40 taper, the ER32 thread, and the flange in a single CNC turning and milling cycle. Then we carburize the part to a case depth of 0.8 to 1.2 mm and quench to a surface hardness of HRC 58-62. The core stays tough at HRC 30-35, so the chuck absorbs shock without cracking.
The pull stud (also called retention knob) is made from 40CrMo and hardened to HRC 38-42. We torque it to the specified value for the SK40 spindle interface, and we mark the torque value on the body for your maintenance team. The taper is ground on a dedicated cylindrical grinder, then lapped to a surface finish of Ra 0.4. The outer diameter is turned to Ra 1.6, which keeps chips from sticking and makes cleanup faster.
Runout is not an accident; it is a sequence of controlled steps. First, we stress-relieve the raw bar before machining to remove internal stresses. Second, we machine the ER32 bore and the SK40 taper in the same clamping setup, so both features reference the same centerline. Third, we heat treat, which introduces distortion, so we grind the taper after hardening. Finally, we assemble the collet nut and test runout with a precision ground test bar.
We test each chuck with a 10 mm test bar clamped at 3 times the collet length. The reading at the nose is typically 0.003 mm, and at 100 mm from the nose it stays under 0.008 mm. If a unit fails, we do not rework it; we scrap it and machine a new one. That policy keeps our average runout at 0.004 mm, which is better than ISO 10897 class AT3 requirements.
Every SK40 ER32 chuck goes through a 12-point inspection before it is packed. We check the taper angle with a precision air gauge, verify the thread with a GO/NO-GO plug gauge, and measure hardness on a Rockwell tester. We also run the runout test described above and record the value on the inspection certificate. The certificate includes the batch number, material heat number, and the operator's name.
For orders above 10 pieces, we include a full dimensional report with CMM data for the taper, the collet pocket, and the flange face. This report is free and is sent with the shipment. We keep a sample of every batch for 24 months, so if you have a field issue, we can trace the part back to the exact heat and machining shift.
Standard surface finish is a black oxide on the body, which gives a uniform appearance and mild corrosion resistance. The taper face is left ground and bright. If you run aluminum or other sticky materials, we can apply a titanium nitride (TiN) coating on the outer body. TiN reduces chip adhesion and increases wear resistance on the flange, at an added cost of about 8% per unit. We also offer a passivated stainless steel version for cleanroom or medical applications, but the standard alloy steel is suitable for 95% of CNC milling and drilling jobs.
This SK40 ER32 chuck is balanced to G2.5 at 15,000 RPM as standard. If your spindle runs faster, we can balance to G1.0 at 20,000 RPM for an extra charge. The ER32 collet nut is a standard slotted hex type, and we recommend a torque of 65 Nm for 10 mm tool shanks. Over-tightening does not reduce runout; it only bends the collet. We print the recommended torque range on the nut itself, so your operators do not need to check a chart.
For high-speed milling above 12,000 RPM, we suggest ordering the chuck with our balanced nut option, which has a machined relief to reduce air turbulence. This option adds 3 days to lead time but reduces noise and heat at the spindle interface.
| Specification | Value |
|---|---|
| Taper interface | SK40 (BT40 option available) |
| Collet type | ER32 (2 mm – 20 mm clamping range) |
| Body material | 20CrMnTi alloy steel |
| Surface hardness | HRC 58 – 62 (case depth 0.8 – 1.2 mm) |
| Core hardness | HRC 30 – 35 |
| Pull stud material | 40CrMo, HRC 38 – 42 |
| Runout (TIR at nose) | ≤ 0.005 mm (typical 0.003 mm) |
| Runout at 100 mm | ≤ 0.008 mm |
| Taper surface finish | Ra 0.4 (ground and lapped) |
| Body surface finish | Ra 1.6 (black oxide) |
| Balancing | G2.5 @ 15,000 RPM (G1.0 @ 20,000 RPM optional) |
| Lead time | 15 days (standard), 7 days (express, 30% surcharge) |
| MOQ | No MOQ (single piece accepted) |
| Inspection | 12-point check, CMM report for orders >10 pcs |
If you need a longer gauge length or a different taper, we can adjust the drawing within 2 days. Common modifications include a 160 mm or 200 mm overall length, a through-coolant hole down the center, or a modified flange for automatic tool changers. We also make BT40 and CAT40 versions from the same raw material and heat treatment line. For a custom length, the price increases by roughly 15% and lead time extends to 20 days.
Send us your tool list or your existing chuck drawing, and we will match the critical dimensions. Our engineers will check the fit of your ER32 collets and the pull stud thread pitch (MAS403 or ANSI standard). We have made over 2,000 custom tool holders for export clients, so most requests are not new to us.
When you receive the chuck, do a simple runout check before mounting it on the spindle. Clean the taper and the spindle socket, insert the chuck, and pull it tight. Clamp a precision test bar in an ER32 collet and indicate the bar at 10 mm from the collet nose. Our parts will read below 0.005 mm. If you see higher runout, check the collet itself for debris or damage—90% of runout problems come from dirty collets, not the chuck.
We also recommend checking the pull stud torque after the first 100 hours of use. Thermal cycling can slightly loosen the stud. Re-torque to 45 ft-lb for SK40 and mark the position with a paint pen. This simple step prevents tool pullout in heavy roughing.
Each chuck is wrapped in VCI (vapor corrosion inhibitor) paper, placed in a foam-lined box, and then packed in a wooden crate for sea freight or a double-wall carton for air freight. For orders under 5 kg, we ship via DHL or FedEx, with a delivery time of 3-5 days to most countries. For larger orders, we use FOB Shenzhen or CIF any major port. We provide a commercial invoice, packing list, and certificate of origin—all free of charge.
All our products are made in China at our Dongguan factory, which has been operating since 2005. We are an ISO 9001:2015 certified facility, and we export to 30+ countries. If you need a specific inspection report format for your ISO audit, just tell us in advance—we will format the certificate to your requirement.
No MOQ—you can order a single SK40 ER32 chuck for testing, and the price per piece only drops slightly for quantities above 20.
Yes, we can modify the overall length, add a through-coolant hole, or change the pull stud standard (MAS403, ANSI, or DIN) within 2 days of drawing approval.
We grind the taper after heat treatment and test every chuck with a calibrated test bar, scrapping any unit above 0.005 mm TIR.
Standard 15 days, custom 20 days, and express 7 days with a 30% surcharge, not including shipping time.
If you are deciding between tool holder types, read our 'CNC cutting tool selection guide' for a comparison of ER, shrink fit, and hydraulic chucks. For tolerance definitions across different machining processes, our 'CNC machining tolerances guide' explains how ISO and ANSI standards apply to tool holders.
Send us your drawing or a photo of your current chuck, and we will confirm price and lead time within 12 hours. Email sc@bquq.com or WhatsApp +86 13713157787. Precision manufacturing is our core—every BQUQ chuck is machined, hardened, and inspected in our own factory in Dongguan, China. No MOQ, no middlemen, no delays.
| 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 |
