What This ER25 Chuck Is and Why It Holds Tighter Than Your Current Holder This is a CNC machined ER25 spring collet chuck designed to grip end mills from 1 mm to 16 mm shank diameter. We machine it
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What This ER25 Chuck Is and Why It Holds Tighter Than Your Current Holder This is a CNC machined ER25 spring collet chuck designed to grip end mills from 1 mm to 16 mm shank diameter. We machine it
This is a CNC machined ER25 spring collet chuck designed to grip end mills from 1 mm to 16 mm shank diameter. We machine it from 42CrMo4 alloy steel, heat-treated to HRC 58-62, then precision-ground to a concentricity of 0.005 mm TIR at the nose. That means you get less tool deflection at depth, better surface finish on your workpiece, and longer end mill life—especially in stainless and hardened steel cutting. We ship from Dongguan with a standard 15-day lead time, and we do not enforce a batch minimum.
The ER25 system uses a tapered collet that compresses evenly around the tool shank when you tighten the nut. Unlike set-screw holders, the clamping force is applied over the full contact length—typically 10 mm to 12 mm of engagement in our pocket design. That eliminates point-loading, so your end mill shank stays round and free of brinelling marks. We machine the internal taper to a 8° included angle with a surface finish of Ra 0.4 µm, which ensures the collet seats consistently every time you change tools. The result is repeatable runout under 0.005 mm, even after 500+ tool changes.
We make the chuck body from 42CrMo4 (AISI 4140) because it balances toughness and machinability. The body is hardened to HRC 58-62, then tempered to reduce brittleness while keeping yield strength above 900 MPa. The locking nut is made from 20CrMnTi case-hardened steel, carburized to a surface hardness of HRC 58-62 with a core hardness of HRC 30-35. This combination gives you a wear-resistant thread and a tough core that resists cracking under repeated high-torque tightening. We do not use 1215 free-machining steel—it cannot hold the required hardness or fatigue life for production cutting.
We start with a solid bar, not a casting. Our 5-axis CNC lathes turn the external profile to within 0.01 mm. Then we mill the drive flats and the thread relief. The internal taper is semi-finish bored, then heat-treated, and finally ground on a CNC internal grinder with a CBN wheel. The grinding pass removes only 0.2 mm of stock, which keeps heat distortion below 0.002 mm. After grinding, we lap the taper against a master collet to achieve a bearing contact of at least 85% across the taper surface. This is not a standard commercial tolerance—this is what gives you consistent tool holding for high-speed machining.
Every single chuck is checked, not just one per lot. We use a CMM with a probe resolution of 0.0005 mm to verify the taper angle, the thread pitch, and the concentricity of the bore to the taper. Runout is measured with a dial indicator on a precision mandrel—we reject anything above 0.005 mm TIR. Surface hardness is verified with a Rockwell tester on the body and the nut. We also do a functional test: we clamp a standard 10 mm end mill shank and measure the runout at the nose and at 3× diameter from the nose. You get a copy of the inspection sheet with your shipment. If you need a full material certificate or a PPAP level 3 report, we can provide that at no extra charge.
We machine these chucks to match ISO 15488 (DIN 6499) dimensional standards. That means you can use any standard ER25 collet from any brand—we do not lock you into our collets. The thread on the nut is M40×1.5, and the shank is available in straight cylindrical, CAT40, BT40, or HSK63A configurations. If you need a custom shank length or a special thread, we can modify the design in your drawing. Below is the standard specification table for our most common configuration: the straight shank with an internal coolant hole.
| Parameter | Value |
|---|---|
| Collet type | ER25 (ISO 15488 compliant) |
| Clamping range | 1 mm – 16 mm (in 1 mm increments) |
| Shank options | Straight Ø20 mm, CAT40, BT40, HSK63A |
| Body material | 42CrMo4 (AISI 4140) |
| Heat treatment | Hardened & tempered, HRC 58-62 |
| Nut material | 20CrMnTi carburized, HRC 58-62 surface |
| Concentricity (TIR) | 0.005 mm at nose, 0.008 mm at 3×D |
| Surface finish | Ra 0.4 µm on taper, Ra 0.8 µm on body |
| Internal coolant hole | Ø4 mm through, optional |
| Lead time | 15 days standard, 7 days for rush (MOQ 10 pcs) |
| MOQ | No MOQ for standard sizes |
Hydraulic chucks damp vibration better, but they cost 4-5× more and require a hydraulic pump to assemble. Our ER25 chuck gives you 80% of the damping performance at 20% of the cost. For finishing passes on aluminum or pre-machined steel, the difference in surface finish is within Ra 0.2 µm—negligible for most applications. The real advantage is tool change speed: you can swap an end mill in under 30 seconds with a standard torque wrench. That makes this chuck ideal for job shops that run multiple small batches per day. If you need maximum damping for heavy roughing, we would recommend a hydraulic holder—but for 90% of milling work, this ER25 chuck is the correct engineering choice.
We can add a flat on the shank for drive pins, extend the length by up to 50 mm for deep reach, or machine a custom thread on the nut for a locking ring. We also offer a version with a through-coolant hole up to Ø6 mm if you are running through-spindle coolant. For high-speed spindles above 20,000 RPM, we can balance the chuck to G2.5 at 25,000 RPM—just specify the target speed on your drawing. We have machined over 12,000 collet chucks in the last 5 years, and we keep tooling for common variations in stock to cut your lead time.
No MOQ for standard ER25 sizes—you can order one piece for testing, and we offer quantity pricing starting at 10 pieces.
Yes, we can modify the shank diameter, length, thread type, or add a through-coolant hole based on your 2D drawing or 3D STEP file.
Each chuck is inspected on a CMM and a dial indicator mandrel; we reject any unit above 0.005 mm TIR and include the inspection report with your package.
Standard lead time is 15 days from drawing approval; for urgent orders of 10 pieces or fewer, we can ship in 7 days.
We are a precision manufacturing factory in Dongguan, China, with 20 years of CNC machining experience. We have shipped over 200,000 machined parts to engineers in 30 countries. If you are comparing suppliers, use our CNC cutting tool selection guide to check your parameters, and review our CNC machining tolerances guide to confirm your print requirements. For a firm quote on your Cnc Machined Er25 Spring Collet Chuck With End Mill Cnc Machining project, email us at sc@bquq.com or WhatsApp +86 13713157787. Send your drawing (STEP, IGES, or PDF) and we will reply with pricing, lead time, and a DFM review within 12 hours.
| 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 |
