What This 50 Type Collet Does That Standard Chucks Cannot This is a CNC machined auto lathe 50 type collet designed specifically for feeding round bar stock through a sliding headstock or fixed headst
This is a CNC machined auto lathe 50 type collet designed specifically for feeding round bar stock through a sliding headstock or fixed headstock automatic lathe. The concrete benefit is grip repeatability: we hold true radial runout to 0.005 mm TIR (measured at 3 mm from the nose) and axial positioning repeatability within ±0.01 mm. You get this precision for 7 days from drawing approval to shipment, and the gripping surface is hardened to 58–60 HRC so it survives 200,000+ cycles without losing clamp force on cold-drawn steel, brass, or aluminum round bar.
This is not a generic ER collet. The 50 type refers to the body taper and thread pitch (M30 × 1.5 pull-back thread), matching standard auto lathe spindles from Citizen, Star, and Tsugami. The bore is ground to your exact bar diameter, not a range. If your stock is 12.00 mm, the collet grips 12.00 mm — nothing else. That is how we eliminate bar push-back and chatter on high-speed turning.
Soft collets (below 45 HRC) deform under repeated clamping, especially when you run 3-meter bars with a bar feeder. The 50 type collet we machine starts as AISI 4140 alloy steel, then we heat-treat to 58–60 HRC in a vacuum furnace. The gripping segments are then wire-cut and ground to final size. This gives you a hard, wear-resistant surface that does not gall against the bar stock, and the spring-back is consistent — we test every collet for elastic recovery after 500 open-close cycles at full stroke.
The internal bore is honed to Ra 0.4 µm. A smoother bore means less friction on the bar, which reduces heat buildup and prevents scoring on finished parts. For stainless steel (304/316) or titanium, we offer a nitrided version (surface hardness 900 HV) for an additional 2 days of lead time.
We machine the collet bore to your nominal bar size with a tolerance of +0.005 / -0.000 mm. This is a light press fit for the bar, meaning the collet grips on the full 360° circumference. Standard sizes in stock tooling start at 3.00 mm and go up to 50.00 mm in 0.5 mm increments. For odd sizes (e.g., 5.55 mm, 12.7 mm), we machine from solid bar stock on our CNC lathes — no extra tooling charge. The round bar stock we use for the collet body is precision-ground to 0.002 mm straightness before we cut the slots.
The three slots (for 3-segment grip) or six slots (for 6-segment grip on thin-walled bars) are cut by wire EDM. Slot width is 0.5 mm ± 0.05 mm. This design allows the collet to collapse 0.1 mm over the full travel, which is enough to release a bar with a slightly oversized diameter (up to 0.05 mm) without jamming.
| Specification | Value / Range |
|---|---|
| Collet Type | 50 Type (M30 × 1.5 pull-back thread) |
| Body Material | AISI 4140 alloy steel |
| Hardness (Gripping Surface) | 58–60 HRC (nitrided option: 900 HV) |
| Bore Diameter Range | 3.00 mm – 50.00 mm (in 0.5 mm steps) |
| Bore Tolerance | +0.005 / -0.000 mm |
| True Radial Runout (TIR) | 0.005 mm at nose, 0.008 mm at 20 mm depth |
| Surface Finish (Bore) | Ra 0.4 µm (honed) |
| Slot Width | 0.5 mm ± 0.05 mm (wire-cut) |
| Spring-back (after 500 cycles) | < 0.02 mm permanent set |
| Lead Time | 7 days for custom bore, 3 days for standard sizes |
| MOQ | No MOQ (single piece accepted) |
| Country of Origin | Made in China, Dongguan factory (ISO 9001:2015) |
Every collet goes through a 5-step QC gate before it leaves our Dongguan factory. First, we check the taper angle with a sine bar and gauge ball — the 50 type taper is 16° included angle, and we hold it to ±0.01°. Second, we verify the thread pitch with a thread plug gauge (6g tolerance). Third, we measure bore diameter with an air gauge (resolution 0.001 mm). Fourth, we run a live TIR test on a spindle test mandrel — the collet is mounted, a 100 mm precision bar is inserted, and we rotate it at 3000 RPM to confirm runout does not exceed 0.005 mm. Fifth, we record hardness on the gripping surface with a Rockwell tester and attach the certificate to the package.
We also do a functional grip test for every 50-piece batch: we clamp a test bar, apply a 500 N axial pull, and confirm there is zero slip. This is not a spot check — it is a 100% inspection for runout and hardness. You get a PDF report with the actual measured values (not just a "pass" stamp) within 24 hours of shipment.
Many collets on the market are cold-formed or cast, which leaves internal stresses that cause the collet to "walk" (lose concentricity) after a few thousand cycles. Our 50 type collet is fully CNC machined from solid round bar stock — no casting, no welding. The body is turned on a 5-axis CNC lathe, the slots are wire-cut, and the bore is honed. This process eliminates distortion and ensures the three or six gripping segments flex uniformly. In our stress-relief test, a collet returned to within 0.003 mm of its original bore diameter after being clamped and released 10,000 times.
Because we are a precision manufacturing factory (not a trading company), we control the entire process: heat treatment, grinding, wire EDM, and QC. This is why we can offer a 7-day lead time for custom bore sizes — we do not wait for an overseas supplier. If you are unsure about whether a 50 type collet fits your spindle, check the thread and taper against your machine manual, or send us a photo of your current collet. We will match it exactly.
There is no MOQ — we accept a single piece order for any bore size between 3.00 mm and 50.00 mm, and the price per piece stays the same whether you order 1 or 100.
Yes, we offer a 6-segment design for round bar under 6 mm diameter to prevent ovalization, and we can cut internal grooves for hex bar (e.g., 8 mm A/F) — just specify the bar shape and dimensions on your drawing.
We do a 100% live spindle test on a calibrated mandrel for every collet, and the measured TIR value is printed on the inspection certificate that ships with your order; if any unit exceeds 0.005 mm, it is scrapped, not sold.
Standard 50 type collets with custom bore ship in 7 days; if you need a modified body length (e.g., +10 mm) or a different thread (e.g., M32 × 1.5), lead time extends to 10 days because we machine the body from a larger blank.
When you run a CNC auto lathe with a bar feeder, the collet closes on the bar behind the guide bushing. The 50 type collet's pull-back action (threaded on the rear) pulls the bar tight against the spindle stop. The key to long bar feeder life is the collet's exterior surface finish — we grind the outside diameter to Ra 0.8 µm so it slides smoothly inside the spindle liner without galling. The taper angle is matched to the spindle nose, so the collet self-centers each time it closes, even after hundreds of cycles.
For bar stock with a rough surface (hot-rolled, not cold-drawn), we recommend ordering the bore 0.01 mm larger than nominal to avoid binding. For precision-ground bar (tolerance h6), our standard +0.005 mm bore is correct. If you are unsure about your bar tolerance, read our CNC machining tolerances guide — it explains the ISO fit classes and how they affect grip force. Also, if you are selecting a collet for a different spindle type, our CNC cutting tool selection guide covers the differences between ER, 5C, and 50 type systems so you do not order the wrong taper.
Each collet is individually wrapped in VCI (vapor corrosion inhibitor) paper, placed in a foam-lined box, and then packed in a wooden case if you order more than 10 pieces. We ship via DHL, FedEx, or UPS — the freight cost for a single collet (about 0.5 kg) is roughly $35 to the USA or EU, and delivery takes 3–5 days. We also offer a 12-month warranty against manufacturing defects: if the collet cracks, distorts, or fails to hold tolerance under normal use, we replace it free of charge, including shipping.
If you need a custom collet for a machine not listed in our standard catalog (e.g., a 55 type or a special nose taper), send us the spindle drawing or the old collet. Our engineers will reverse-engineer it and provide a CAD confirmation within 48 hours. We have done this for over 200 machine models since our factory opened in 2005. This is precision manufacturing made in China — but with the documentation and traceability you expect from a tier-1 supplier.
Stop guessing whether a stock collet will fit your bar and spindle. Email us your bar diameter, material, and machine model (or a drawing with the thread and taper dimensions), and we will send you a firm quote within 12 working hours. The quote includes the unit price, lead time, and shipping cost to your door — no hidden fees, no MOQ. For a single collet with a custom bore, the typical price is $38–$52 depending on size and surface treatment. Order today and have the collet on your machine in 10 days.
Email: sc@bquq.com
WhatsApp: +86 13713157787
Send your drawing for an exact quote — we accept PDF, STEP, or IGES files.
| 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 |
