What This Chuck Does and Why It Cuts Your Reject Rate This is a 643 Type Round Bore Spring Collet Chuck, CNC machined for auto lathes that grip round stock from 3 mm to 42 mm. The concrete benefit is
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What This Chuck Does and Why It Cuts Your Reject Rate This is a 643 Type Round Bore Spring Collet Chuck, CNC machined for auto lathes that grip round stock from 3 mm to 42 mm. The concrete benefit is
This is a 643 Type Round Bore Spring Collet Chuck, CNC machined for auto lathes that grip round stock from 3 mm to 42 mm. The concrete benefit is simple: you get 0.005 mm TIR (total indicated runout) at the nose, a surface finish of Ra 0.4 µm on the bore, and a hardness of HRC 58-62 on the gripping surface. That means your parts come off the spindle with less vibration, tighter concentricity, and fewer scrap pieces — even on long production runs. We ship standard sizes in 15 days, and custom bores in 20 days, always from our Dongguan factory.
The 643 Type is not a generic ER collet. Its round bore has a specific internal taper angle and a spring slot pattern that closes evenly around the workpiece. Unlike split-step collets, the 643 design applies radial force along the full contact length — not just at the front edge. In our tests, this reduces slippage by 18% compared to standard 5C collets at the same clamping torque. The bore is ground after CNC machining, not just turned, so the gripping surface stays parallel within 0.003 mm across its entire length. If you are turning, milling, or grinding round bar stock, this geometry holds tighter and longer.
We make the body from 8620 alloy steel, not cheap 1045 carbon steel. The reason is case hardenability. We carburize the bore to a depth of 0.8-1.2 mm, then harden to HRC 58-62. The spring slots are cut after heat treatment using wire EDM, so there is no distortion in the hardened steel. The outside diameter is ground to h6 tolerance (0 to -0.013 mm for a 50 mm OD), which lets the chuck seat into your spindle with zero wobble. For the screws, we use 12.9-grade hex socket cap screws, zinc-nickel plated to resist corrosion in coolant-heavy environments. This combination gives you a tool that holds its accuracy past 200,000 cycles.
We do not say "high precision" without proof. Every 643 Type Round Bore Spring Collet Chuck is inspected to these limits before it leaves the factory:
| Parameter | Value |
|---|---|
| Bore diameter range | 3 mm – 42 mm |
| Chuck body OD | 25 mm – 80 mm (h6 tolerance) |
| Concentricity (TIR at nose) | ≤ 0.005 mm |
| Surface finish (bore) | Ra 0.4 µm |
| Hardness (case hardened) | HRC 58-62 |
| Case depth | 0.8 – 1.2 mm |
| Max clamping force | 18 kN (for 42 mm bore) |
| Standard lead time | 15 days |
| Custom bore lead time | 20 days |
| MOQ | No MOQ — order 1 piece |
These numbers are not "best effort." They are measured on a CMM and a precision air gauge, and the inspection report ships with your order. If you need tighter than 0.005 mm, tell us — we have a precision line that goes to 0.003 mm TIR, but the lead time moves to 25 days.
We do not spot-check. Every single 643 chuck gets a full inspection. First, we check the bore diameter with an air gauge (resolution 0.0005 mm) to confirm it is within the drawing tolerance of +0.005 / -0.000 mm. Second, we mount the chuck on a test arbor and measure TIR at three points: front, middle, and rear of the bore. If any point exceeds 0.005 mm, the chuck goes back to the grinding machine — it never ships. Third, we verify hardness on the bore surface with a Rockwell tester, not just the outside. Finally, we test the spring action by clamping a ground pin and measuring the pull-back force. You get a printed report with the part number, date, and operator code. This is standard, not an extra-cost option.
Standard 643 collets come with round bores, but your workpiece might be hex, square, or have a stepped diameter. We can machine custom bore profiles from your drawing in 20 days. The limit is the slot pattern — we can cut slots for hex up to 24 mm across flats, and square up to 20 mm. For stepped parts, we can grind a two-diameter bore with a 0.5 mm radius transition. We also make adapter plates to fit our 643 chuck to your specific spindle nose, whether it is A2-4, A2-5, or a camlock mount. Just send your spindle drawing, and we will confirm the interface within 24 hours. This is part of our precision manufacturing service — we do not force you into a standard that does not fit your machine.
You are buying directly from BQUQ, a 20-year-old factory in Dongguan, China. That means no middleman markup and no communication lag. You talk to engineers who have run CNC lathes and wire EDMs, not sales agents who forward emails. Our factory floor has 32 CNC machining centers and 14 surface grinders, so we control the entire process from raw bar stock to final inspection. Made in China does not mean "low quality" here — it means you get the same tolerances as a Swiss or German shop at roughly 40% lower cost. Ask for our audit report or a video call to see the production line. We are happy to show you the machines that make your chuck.
There is no MOQ — you can order one chuck for testing, and we will ship it DHL or FedEx within 15 days.
Yes, we machine hex, square, and stepped bores from your drawing, with a 20-day lead time for custom profiles.
Every chuck, regardless of order size, goes through the same air gauge, CMM, and hardness inspection, and you get the report.
Standard round bore chucks ship in 15 days; custom bores and adapter plates ship in 20 days from drawing approval.
Stop guessing whether a standard collet will fit your spindle. Send us your workpiece diameter, spindle nose type, and desired runout. We will reply within 12 hours with a firm price, a confirmed lead time, and a DFM note if we see a way to improve your part's grip. For a faster response, include your drawing in STEP or PDF format. Email us at sc@bquq.com or message us on WhatsApp at +86 13713157787. No MOQ, no obligation, just a straight answer from the factory floor.
Before you finalize your tooling, read our CNC cutting tool selection guide to match this chuck with the right inserts and holders. And if you are specifying tolerances for a new job, check our CNC machining tolerances guide to avoid over-specifying — it will save you money on every batch.
| 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 |
