This is a CNC machined auto lathe collet set covering sizes 20, 30, and 40 – the "mid collection" for medium-duty turning and milling spindles. You get guaranteed 0.005 mm TIR (total indicated runout)
This is a CNC machined auto lathe collet set covering sizes 20, 30, and 40 – the "mid collection" for medium-duty turning and milling spindles. You get guaranteed 0.005 mm TIR (total indicated runout), a surface finish of Ra 0.4, and a hardness of HRC 58-62, all from a single precision manufacturing batch in our Dongguan factory. Lead time is 7 working days for standard sizes, and we hold stock for immediate shipment.
Auto lathes run at 6,000 to 12,000 RPM. Any runout above 0.008 mm causes chatter marks on the finished part and shortens insert life by up to 30%. Our collets are ground in one clamping operation, so the bore and the taper share the same centerline. You get repeatable gripping force of 4,500 N for the 20 size, 6,200 N for the 30, and 8,500 N for the 40. This means your bar stock stays centered even when you push feed rates to 0.25 mm/rev.
We start with 42CrMo4 or equivalent AISI 4140 alloy steel – not cheap 1045. The blank is turned, then hardened in a vacuum furnace to avoid decarburization. Tempering brings the hardness to HRC 58-62 across the entire body, not just the nose. After hardening, we grind the OD and the internal bore to tolerance class H6. For the slotted segments, we use wire EDM to cut 12 slots with a 0.5 mm width, ensuring even springback when you release the collet.
Each collet in this set has a staggered slot pattern – three full slots and three partial slots for the 20 size, four full and four partial for the 30, and five full and five partial for the 40. This geometry distributes radial force evenly. We chamfer every slot edge at 0.2 mm x 45° to prevent stress risers. You can open the collet up to 0.5 mm beyond its nominal size without permanent set. That is a 200% improvement over standard parallel slotted collets.
Every single collet is checked on a CNC coordinate measuring machine (CMM) with a resolution of 0.001 mm. We measure the taper angle, the bore diameter, and the runout at three points: the nose, the middle, and the back. The acceptance criterion is 0.005 mm TIR, but 85% of our parts come out under 0.003 mm. We also test the hardness on a Rockwell tester on two spots per part. If a collet fails, it goes to scrap – we do not rework slots.
The standard finish is Ra 0.4 on all functional surfaces – the taper, the bore, and the slots. This is achieved with a fine grinding pass using a 400-grit wheel. If you run coolant with chlorine additives, we recommend a TiN coating on the gripping area, which adds 2,000 hours of wear life. For dry runs, a black oxide finish is included free of charge. The coating thickness is 2-4 microns, which does not affect the tolerance.
We keep 500 sets of each size in stock. For standard 20/30/40 sets, the lead time is 7 working days from your purchase order. There is no MOQ – you can order one set or one hundred sets. Each collet is individually wrapped in anti-rust paper, then packed in a partitioned ABS box with a laser-etched size label. For bulk orders of 50 sets or more, we provide a wooden case with foam inserts, ready for sea freight or air cargo.
These collets match DIN 6499 and ISO 15488 standards, so they fit most Japanese, German, and Chinese auto lathe spindles. The taper angle is 8° per side for sizes 20 and 30, and 16° for the size 40. The pull-back stroke is 2 mm for all sizes, which is standard for hydraulic or pneumatic actuators. If you have a custom spindle nose, we can modify the back face – just send us a drawing of the mating surface.
| Specification | Value for Size 20 | Value for Size 30 | Value for Size 40 |
|---|---|---|---|
| Material | 42CrMo4 / AISI 4140 | 42CrMo4 / AISI 4140 | 42CrMo4 / AISI 4140 |
| Hardness (HRC) | 58-62 | 58-62 | 58-62 |
| Clamping Range (mm) | 1.0 – 20.0 | 3.0 – 30.0 | 5.0 – 40.0 |
| Runout (TIR, mm) | 0.005 | 0.005 | 0.005 |
| Bore Tolerance | H6 | H6 | H6 |
| Surface Finish (Ra) | 0.4 | 0.4 | 0.4 |
| Slot Count | 6 | 8 | 10 |
| Max Opening (mm) | +0.5 | +0.5 | +0.5 |
| Lead Time (working days) | 7 | 7 | 7 |
| MOQ | No MOQ | No MOQ | No MOQ |
We have no MOQ – you can order a single set of 20, 30, or 40, or a mixed set of all three sizes.
Yes, we can grind the bore to any diameter between 1 mm and 40 mm, with a tolerance of H6, and ship within 10 working days.
We send a CMM inspection report with each shipment, showing the measured runout at three axial positions on every collet.
For 100 sets, we deliver in 15 working days because we need to run two production batches, but you can get the first 20 sets in 7 days.
For a firm quote within 12 hours, email your drawing or part list to sc@bquq.com. For urgent requests, call or WhatsApp +86 13713157787. If you are comparing tooling options, check our CNC cutting tool selection guide to match collets with your inserts. To set realistic tolerances for your next part, read our CNC machining tolerances guide – it explains how runout relates to part quality. This CNC Machined Auto Lathe Collet Set 20 30 40 Mid Collection is precision manufacturing, made in China, with no MOQ – send your drawing 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 |
