This is a BT40 collet chuck tool holder with an ER32 spring collet, machined from a single billet of 20CrMnTi alloy steel. It holds your end mills and drills with a TIR (total indicated runout) of ≤0.
This is a BT40 collet chuck tool holder with an ER32 spring collet, machined from a single billet of 20CrMnTi alloy steel. It holds your end mills and drills with a TIR (total indicated runout) of ≤0.005 mm at the nose, and the collet taper is ground to a 16° included angle with a surface finish of Ra 0.4 µm. We ship standard sizes in 15 days, and the gripping surface is case-hardened to HRC 58-62 for long service life in high-torque CNC milling.
An ER collet is a slotted steel sleeve that collapses radially when the chuck nut is tightened. The BT40 taper (7:24) seats the chuck body into the spindle, while the collet’s internal bore grips the tool shank with a clamping range of 1 mm per collet size. For example, an ER32 collet covers 2–20 mm tool diameters, with each individual collet spanning a 1 mm range (e.g., 10–11 mm, 11–12 mm). This eliminates the need for hydraulic expansion or induction heating, so tool changes take under 30 seconds on the shop floor.
The chuck body is machined from 20CrMnTi, a low-carbon alloy steel that responds well to carburizing. We case-harden the taper and the collet seat to a depth of 0.8–1.2 mm, reaching a surface hardness of HRC 58-62. The core remains tough at HRC 30-35, which absorbs vibration during interrupted cuts. The pull stud (MAS BT-403 style) is made from 42CrMo and through-hardened to HRC 40-45, so it won’t stretch under a 10,000 rpm spindle load.
Most suppliers grind the taper and the collet pocket separately, which causes runout to stack up. We grind the BT40 taper first, then mount the body on a precision arbor to grind the collet seat concentric to that same taper. Final assembly runout is checked with a 10 mm test bar inserted into the collet. Our standard is ≤0.005 mm at 50 mm from the nose; if you need ≤0.003 mm for finishing passes, we can select and match individual collets at a small surcharge.
The external surfaces are finished to Ra 0.8 µm, while the taper and collet seat are ground to Ra 0.4 µm. As standard, we apply a black oxide finish that resists light rust and improves lubricity. For coolant-heavy environments, we offer a titanium nitride (TiN) coating on the chuck body, which raises surface hardness to HV 2200 and lowers the friction coefficient. The coating adds 3 days to the lead time but is recommended for aluminum machining where chips tend to weld onto steel.
Each BT40 chuck is checked with a taper gauge for contact area — we require at least 90% contact across the 7:24 cone. The pull stud is torqued to 65 N·m and marked with a torque stripe to show it hasn’t loosened in transit. We also verify the collet nut thread (M40 × 1.5) with a go/no-go gauge, and we record the serial number on the body so you can trace the heat lot and grinding date back to our factory in Dongguan.
We run a 4,500 m² plant with 20 CNC lathes and 12 cylindrical grinders, so we don’t need to batch your order with other customers to make money. You can order a single BT40 collet chuck for testing, or 500 pieces for a production line. The cost per unit drops from $38 at qty 1 to $22 at qty 50, excluding the collets. All our precision manufacturing is done in-house, from the raw billet to the final grind, which is why we can hold tolerances that match Japanese or German brands at 60% of the price.
| Parameter | Value |
|---|---|
| Shank taper | BT40 (MAS BT-403) 7:24 |
| Collet type | ER32 spring collet |
| Collet clamping range | 2–20 mm (1 mm steps) |
| Chuck body material | 20CrMnTi alloy steel |
| Pull stud material | 42CrMo, HRC 40-45 |
| Surface hardness | HRC 58-62 (case depth 0.8–1.2 mm) |
| Runout (TIR) | ≤0.005 mm at 50 mm from nose |
| Surface finish (taper) | Ra 0.4 µm |
| Surface finish (body) | Ra 0.8 µm, black oxide or TiN |
| Lead time | 15 days standard, 18 days with TiN |
| MOQ | No MOQ, single piece accepted |
There is no MOQ — order one piece for a sample test or a full production batch, and pricing automatically adjusts based on quantity.
Yes, we can supply MAS BT-403, BT-404, or a Japanese standard pull stud, and we can change the nut type from a standard hex to a flat or locking style at no extra tooling cost.
Every chuck, regardless of quantity, goes through the same taper gauge, runout test, and torque stripe inspection, and we email you the inspection report with the serial number.
Standard BT40 collet chucks ship in 15 days; if you need a longer gauge length or a non-standard collet seat, we quote 20 days because we re-machine the grinding fixture.
For a firm quote within 12 hours, email your drawing or a simple sketch with the collet size, tool shank diameter, and your spindle taper to sc@bquq.com. You can also reach us on WhatsApp at +86 13713157787. If you are still comparing holder types, read our CNC cutting tool selection guide to see when a collet chuck beats a shrink fit holder, and check our CNC machining tolerances guide to understand which runout class you actually need for your parts.
| 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 |
