What This 25 Type Collet Does for Your Auto Lathe Spindle This is a CNC machined auto lathe 25 type collet designed to hold round bar stock up to 25 mm diameter. It delivers 0.005 mm total runout at t
This is a CNC machined auto lathe 25 type collet designed to hold round bar stock up to 25 mm diameter. It delivers 0.005 mm total runout at the nose and a 58 HRC hardened gripping surface. You get repeatable clamping force for bar feeding operations, with a standard 15-day lead time from our Dongguan factory.
We start with alloy steel rounds, then CNC turn the OD and ID in one setup. The slot pattern is cut by wire EDM, not milling, so the collet flexes evenly when compressed. We grind the bore after hardening to hold 0.005 mm runout relative to the taper. Each collet is tested against a ground master bar before it leaves the shop. This is precision manufacturing, not a cast or stamped copy.
We use 65Mn spring steel or 20CrMnTi alloy steel, depending on your stock material. 65Mn gives you 58-60 HRC after oil quenching. 20CrMnTi is carburized to 0.8 mm case depth for heavy-duty bar pulling. Both are tempered to eliminate brittleness. The taper seat is nitrided to reduce friction against the nut. You get a collet that holds its shape after thousands of cycles.
The 25 type collet accepts round bar stock from 5 mm to 25 mm in 0.5 mm steps. Concentricity between the bore and the outer taper is held to 0.005 mm. The gripping bore tolerance is H8, which means a 20 mm bar seats with a 0.033 mm clearance max. Surface finish on the bore is Ra 0.4, so it does not scratch soft brass or aluminum. These numbers are verified on a Zeiss CMM, not guessed.
Every collet gets a 100% dimensional check with air gauges. We measure bore diameter, taper angle, and slot width. Runout is tested on a dedicated spindle with a dial indicator at 5 mm from the nose. Hardness is sampled per batch with a Rockwell tester. We keep a traceable report for 3 years. If a collet fails any check, it goes to scrap, not to your box.
| Specification | Value | Notes |
|---|---|---|
| Collet Type | 25 type auto lathe collet | Fits standard 25 series spindle nuts |
| Bar Stock Capacity | 5 mm – 25 mm | In 0.5 mm increments |
| Material Options | 65Mn spring steel / 20CrMnTi | Carburized option for heavy duty |
| Hardness | 58 – 60 HRC | Case depth 0.8 mm for carburized |
| Runout (TIR) | 0.005 mm | Measured at 5 mm from nose |
| Bore Tolerance | H8 | Example: 20 mm bar = +0.033 mm |
| Surface Finish (Bore) | Ra 0.4 | Ground and honed |
| Taper Angle Accuracy | ±0.002° | Wire EDM slot geometry |
| Lead Time | 15 days standard | 7 days for rush orders |
| MOQ | No MOQ | Single piece available |
We cut three slots at 120° apart, leaving a thin hinge web at the back. This design lets the collet close evenly without twisting. The slot width is 0.4 mm, which is narrow enough to prevent chips from jamming. We do not cut the slots all the way through, so the collet cannot over-compress and damage your bar. Clamping force is repeatable within ±3% from cycle to cycle.
A 25 type collet grips the bar along its full length, not just at the nose. This reduces vibration during cutoff and drilling. ER collets are designed for tool holding, not bar pulling, so they wear out faster under axial load. Our collet has a hardened taper that mates directly with the spindle nose, eliminating the need for a separate adapter. You save spindle length and reduce runout stack-up.
No MOQ – we can produce a single custom 25 type collet for you, though per-piece price is lower at 10 pieces or more.
Yes, we can modify the bore shape to square, hex, or keyed profiles, but round bar stock is the standard configuration we keep in stock.
We use a dedicated grinding fixture that indexes off the taper, and each collet is individually measured with a dial indicator before packaging.
For 100 pieces of a standard size, we ship in 15 days; for a custom bore diameter, add 3 days for tooling setup.
If you are feeding round bar into a sliding headstock lathe, the collet bore must match your bar diameter closely. A 0.1 mm oversize bore will cause the bar to slip under heavy cuts. For best results, order the collet 0.02 mm larger than your bar's nominal diameter. This gives you a light interference fit without galling. For related tooling decisions, check our CNC cutting tool selection guide to avoid spindle overload.
You need to know your spindle taper angle (usually 30° or 45°) and the collet thread size. We stock both metric and inch thread options. If you are not sure, send us a drawing of your current collet or spindle nut. We will match it exactly. For more on how we hold tolerances, read our CNC machining tolerances guide to understand what H8 and 0.005 mm mean in your process.
We run 12 CNC lathes and 4 wire EDM machines in Dongguan, China. Our quality lab has a Zeiss CMM, a Rockwell tester, and a surface profilometer. We have been making precision collets and springs since 2004. Every 25 type collet is made in China with full material traceability. We export to Europe, North America, and Southeast Asia weekly.
Send us your bar diameter, spindle type, and quantity. We reply with a firm price and delivery date within 12 hours. No MOQ, no hidden tooling fees. Email your drawing to sc@bquq.com or message us on WhatsApp at +86 13713157787. If you have a worn sample, ship it to us and we will reverse-engineer it for free.
| 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 |
