What This Collet Actually Does for Your Swiss-Type or Auto Lathe This is a Cnc Machined Auto Lathe 42 Type Hex Bore Spring Collet—a workholding component that grips hexagonal bar stock (sizes 4 mm to
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What This Collet Actually Does for Your Swiss-Type or Auto Lathe This is a Cnc Machined Auto Lathe 42 Type Hex Bore Spring Collet—a workholding component that grips hexagonal bar stock (sizes 4 mm to
This is a Cnc Machined Auto Lathe 42 Type Hex Bore Spring Collet—a workholding component that grips hexagonal bar stock (sizes 4 mm to 42 mm) on 42-type automatic lathes and CNC sliding-head machines. The concrete benefit is clamping repeatability: we hold concentric runout to ≤0.005 mm and bore tolerance to H6, which means your machined hex parts stay within ±0.01 mm across a full production run. Hardness is 58–62 HRC after vacuum heat treatment, so the collet survives over 200,000 cycles without losing grip force. Lead time is 7 business days for standard sizes, 12 days for custom bores. All manufacturing is done in-house at our Dongguan factory—precision manufacturing, made in China, with no MOQ required.
The hex bore is not a simple drilled hole. We broach the internal hex profile with a tolerance of 0.005 mm per flat, then grind the OD to a concentricity of 0.003 mm relative to the bore. This dual-ground alignment is what stops the bar from twisting or pulling back during heavy cutting. The spring slots are wire-cut EDM, not milled—this gives a consistent slot width of 0.8 mm ±0.02 mm, which ensures even radial compression when the collet closes. On a 42-type machine, the closing nut applies force to the tapered nose; our taper angle is ground to 30° ±0.05°, matching the machine's spindle nose exactly. The result: no vibration, no bar chatter, and no re-tightening mid-cycle.
We start with either 20CrMnTi (case-hardening steel) or 9SiCr (alloy tool steel), depending on your bar material and cutting load. For stainless or titanium bars, we recommend 20CrMnTi with carburizing depth of 0.8–1.2 mm. For standard steel and aluminum, 9SiCr is the better choice. Both materials go through the same process: rough machining → vacuum heat treatment → deep cryogenic treatment (to -120°C) → tempering → finish grinding. The cryo step is the differentiator. It converts retained austenite to martensite, which is why our collets reach 58–62 HRC uniformly across the wall thickness—not just the surface. After final grinding, we perform a magnetic particle inspection on every single piece to check for micro-cracks in the slots.
Every collet is inspected on a Zeiss CMM, not a go/no-go gauge. We check five parameters on each unit: bore diameter (H6 tolerance), hex flat-to-flat dimension (0.005 mm), taper angle (30° ±0.05°), concentricity between bore and OD (0.003 mm), and surface finish on the bore (Ra 0.4). The runout test is done with a real 20 mm hex bar inserted into the collet, mounted on a test mandrel, and rotated at 500 rpm. We record the TIR (total indicated runout) and include the printout in your shipment. If the collet fails any parameter, it goes to scrap—we do not sell B-grade parts or rework them for resale. This is why our return rate over the last 5 years is 0.3%.
| Product Type | CNC Machined Auto Lathe 42 Type Hex Bore Spring Collet |
| Available Hex Sizes | 4 mm, 5 mm, 6 mm, 8 mm, 10 mm, 12 mm, 14 mm, 16 mm, 18 mm, 20 mm, 22 mm, 24 mm, 27 mm, 30 mm, 32 mm, 36 mm, 42 mm |
| Bore Tolerance | H6 (e.g., for 10 mm hex: +0.009 / 0) |
| Concentricity (Bore vs OD) | ≤0.003 mm |
| Runout (with test bar) | ≤0.005 mm TIR |
| Hardness | 58–62 HRC (vacuum heat treated + cryo) |
| Surface Finish (Bore) | Ra 0.4 µm (ground) |
| Material Options | 20CrMnTi (carburized) or 9SiCr (tool steel) |
| Slot Width | 0.8 mm ±0.02 mm (wire-cut EDM) |
| Taper Angle | 30° ±0.05° (ground) |
| Lead Time | 7 business days (standard), 12 days (custom bore) |
| MOQ | No MOQ (single piece accepted) |
| Packaging | Individually wrapped in VCI paper, foam-lined box |
Before you order, measure your hex bar's flat-to-flat dimension with a micrometer—not calipers. If your bar is at the low end of the tolerance (e.g., 19.98 mm for a nominal 20 mm), we will bore the collet to 19.98 mm +0.009 instead of a nominal 20 mm H6. This is a free adjustment we make on every order—never a reason to upcharge. For cutting loads above 0.5 mm depth of cut in stainless steel, specify the 20CrMnTi material option. For aluminum or brass, the 9SiCr option is cheaper and performs identically. If you are unsure which material suits your machine, send us your spindle type, bar diameter, and typical RPM. We will recommend the correct collet within 4 hours. For a deeper understanding of how collet geometry interacts with tool paths, our CNC cutting tool selection guide covers the relationship between workholding and tool deflection. And for the full math behind our H6 and 0.005 mm tolerances, see our CNC machining tolerances guide.
We make custom hex bores from 3 mm to 45 mm, in any increment of 0.1 mm. We also machine square bores, octagon bores, and double-hex (12-point) profiles on the same 42-type body. If your machine uses a 20° taper instead of 30°, we can regrind the nose to match—this requires a 10-day lead time and an additional 15 USD per unit. For long bars (over 3 meters), we can add a counter-bore relief at the back end to prevent bar whip. Custom bore sizes do not change the MOQ—still no MOQ. We only ask that you send us a sketch or drawing of the hex dimensions and the bar tolerance range. We will confirm the H6 calculation against your bar's actual measured size before we cut any steel.
There is no MOQ—you can order a single collet for prototype work, and the unit price stays the same as for 100 pieces.
Yes, we can bore any hex size from 3 mm to 45 mm in 0.1 mm increments, and regrind the taper angle from 20° to 35° to match your spindle nose.
We use a Zeiss CMM to verify 5 critical parameters per unit, plus a real-bar runout test at 500 rpm, and we include the inspection printout in every shipment.
Standard sizes ship in 7 business days; custom bores or taper regrinds take 12 business days, and expedited 5-day service is available for an 8% surcharge.
We respond to every inquiry with a firm quote—not a ballpark range. Send us your hex bar size, material type, machine model (e.g., Star SR-38, Tsugami BS-26, Citizen L32), and your desired bore tolerance if it differs from H6. We will confirm the exact collet configuration, unit price, and shipping cost to your port. Email sc@bquq.com or WhatsApp +86 13713157787. If you send a drawing, we will also check the hex profile against our broaching capabilities and confirm the slot width adjustment needed for your bar's corner radius. Precision manufacturing, made in China, with no MOQ—your quote is waiting.
| 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 |
