This is a CNC machined auto lathe 20 type square bore spring collet engineered for gripping square or hex stock with zero deformation. You get a guaranteed 0.005 mm TIR runout, a
BQUQ CNC Machined Auto Lathe 20 Type Square Bore Spring Collet
This is a CNC machined auto lathe 20 type square bore spring collet engineered for gripping square or hex stock with zero deformation. You get a guaranteed 0.005 mm TIR runout, a hardness of HRC 58–6
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This is a CNC machined auto lathe 20 type square bore spring collet engineered for gripping square or hex stock with zero deformation. You get a guaranteed 0.005 mm TIR runout, a hardness of HRC 58–60, and a 15-day production lead time from our Dongguan factory. Built for high-volume Swiss-type and automatic lathe operations, this collet holds square bar from 3 mm to 20 mm without marring the workpiece surface.
Why a Square Bore Collet Beats Round Jaws for Auto Lathe Work
Square stock slips in round jaws. That costs you cycle time and scrap. This collet’s square bore matches the workpiece geometry exactly, distributing clamping force across four flat faces instead of four points. You get 30% more torque transmission than a round bore collet on the same material. The spring steel body flexes within a controlled range, so you can load and unload parts in under 2 seconds without hydraulic assist.
Material Grade and Heat Treatment Sequence We Use
We start with 65Mn spring steel or SK5 high-carbon steel, depending on your batch size. For stainless or hardened workpieces, we recommend the SK5 version with a nitrided surface. The heat treatment cycle is: quench at 830°C, oil cool, temper at 380°C for 2 hours, then deep-freeze at -80°C for stress relief. Final hardness lands at HRC 58–60, measured on the Rockwell C scale at three points per collet. Surface finish on the bore is Ra 0.2 µm, which prevents galling on soft aluminum or brass.
Runout Control: From Raw Tube to Final Grind
Runout is not an afterthought. We grind the OD and bore in a single clamping setup on a CNC cylindrical grinder, holding the 20 type taper to within 0.003 mm. Then we test each collet on a precision mandrel at 20 mm from the nose. The maximum allowable TIR is 0.005 mm. That number is printed on the inspection card shipped with your order. We reject anything above 0.005 mm—no exceptions, no rework to loosen tolerance.
Dimensional Range and Slot Geometry for 20 Type Auto Lathes
This collet fits standard 20 type auto lathe spindles (e.g., Citizen, Tsugami, Star, Hanwha). The square bore sizes we stock: 3, 4, 5, 6, 8, 10, 12, 14, 16, 18, 20 mm. Slot width is 1.2 mm with a 60° relief angle at the base to prevent stress fractures. The collet head OD is 20.00 mm (+0.000 / -0.005 mm), and the taper angle is 16° included. Each collet weighs approximately 85 grams, so shipping cost per unit stays low.
Inspection Before Every Shipment: Not Just a Paper Stamp
Every single collet goes through a four-step check before packing. Step one: hardness test on a Mitutoyo HR-530. Step two: bore dimension check with a 3-point internal micrometer. Step three: runout test on a coaxial indicator with a calibrated test bar. Step four: visual inspection under 10x magnification for burns or micro-cracks. We keep a digital record for 5 years. If you find a defect within 30 days, we replace it free and cover freight.
Parameter
Value
Material
65Mn spring steel / SK5 high-carbon steel
Hardness
HRC 58–60
Square bore size range
3 mm – 20 mm
Head OD
20.00 mm (+0.000 / -0.005 mm)
Taper angle
16° included
Runout (TIR)
≤ 0.005 mm at 20 mm from nose
Bore surface finish
Ra 0.2 µm
Slot width
1.2 mm with 60° relief
Lead time
15 days standard, 7 days for rush
MOQ
No MOQ – we accept single piece orders
How to Match This Collet to Your Workpiece Material
For soft materials (aluminum, brass, copper), use the 65Mn version with standard slot. For hardened steel above HRC 40, order the SK5 version with nitrided surface—it resists wear 3x longer. For hex stock, we can modify the bore to hex shape at no extra tooling cost for orders above 20 pieces. For square bar with sharp corners, specify corner radius on your drawing; we hold radius to 0.1 mm tolerance.
Packaging and Shipping from Dongguan to Your Door
Each collet is individually wrapped in anti-rust paper, placed in a foam insert, and boxed with a QC report. For orders under 5 kg, we ship via DHL or FedEx, typically 3–5 days to the US or EU. For larger orders, sea freight with wooden pallet packaging is available. We mark every box with the part number, batch code, and your PO number. No mixed lots in one box—traceability is guaranteed.
What is the minimum order quantity?
No MOQ—order one piece for testing, 1000 pieces for production, we ship both at the same quality standard.
Can you customize the bore size or material?
Yes, we can produce square, hex, or custom-shaped bores from 3 mm to 20 mm, and we can switch to SK5 or 9SiCr alloy steel based on your workpiece hardness.
How do you control quality for a single piece order?
Even a single piece goes through the same four-step inspection (hardness, bore size, runout, visual) and ships with a signed QC card.
What is the lead time for a custom square bore collet?
Standard sizes ship in 15 days; custom shapes or materials take 20–25 days, and we can expedite to 10 days for an extra 15% rush fee.
Need a firm quote? Send your drawing or just the square size and material spec. We reply within 12 hours with a fixed price and delivery date. Email: sc@bquq.com. WhatsApp: +86 13713157787. For more on tool selection, read our CNC cutting tool selection guide. If you are checking tolerance limits for your next job, see our CNC machining tolerances guide. This collet is a precision manufacturing product, made in China, with no MOQ—ready to ship now.
