What This Heavy Duty BT50 Chuck Does Differently This is a CNC machined BT50 ER32 collet chuck tool holder designed for aggressive machining and high-torque spindle applications. It delivers a TIR (ru
This is a CNC machined BT50 ER32 collet chuck tool holder designed for aggressive machining and high-torque spindle applications. It delivers a TIR (runout) of ≤0.005 mm at the nose, a hardness of 58–62 HRC, and a surface finish of Ra 0.4 µm on the taper and bore. Lead time is 15 days for standard sizes, 25 days for custom configurations, and we operate with no MOQ.
Built for heavy duty cutting, this holder grips ER32 collets (1–20 mm capacity) with clamping force that resists pullout during rough milling and drilling. The BT50 taper ensures rigid seating in your spindle, reducing vibration and extending tool life. This is precision manufacturing from our Dongguan factory, made in China, with every unit inspected before shipment.
The ER32 system uses a tapered collet that compresses evenly around the tool shank when the locking nut is tightened. This design distributes clamping force over 360 degrees, eliminating the three-point contact that causes runout in older chuck styles. Our chuck body is machined in one setup from the BT50 taper to the collet seat, meaning the bore and taper share the same datum. This single-setup machining is the reason we hold ≤0.005 mm TIR at 4× tool diameter. For a deeper look at how tool geometry affects cutting performance, see our CNC cutting tool selection guide.
The heavy duty design uses a thicker wall section around the collet pocket, which increases radial stiffness by 15% compared to standard ER32 chucks. This matters when you are pushing 20 mm end mills at full depth in steel. The nut is case-hardened to 60 HRC and features a ground thread profile that resists galling, even after thousands of tool changes.
We start with 20CrMnTi alloy steel, a material chosen for its combination of core toughness and case hardenability. The blank is forged, not cut from bar stock, to align the grain structure with the taper’s stress lines. After rough machining, we carburize the part to a case depth of 0.8–1.2 mm, then harden to 58–62 HRC. This case gives the taper a wear-resistant surface that maintains its geometry under repeated tool changes.
The through-bore is gun-drilled and then honed to Ra 0.4 µm. This is critical for coolant flow—a rough bore creates turbulence that reduces coolant pressure at the cutting edge. We also grind the BT50 taper to AT3 grade, which is the highest precision class per ISO 7388/1. This ensures that when you pull the chuck into your spindle, the contact area exceeds 90%, preventing micro-movement that degrades surface finish.
Every chuck goes through a three-stage inspection process. First, we check the BT50 taper against a master gauge using blueing compound—contact must be at least 90% continuous. Second, we measure TIR at the collet seat using a 10 mm test bar at 4× diameter projection; the reading must be ≤0.005 mm. Third, we verify hardness on the taper and nut using a Rockwell tester, and we record the value on the inspection certificate.
We also perform a coolant flow test at 50 bar pressure to ensure the internal passages are clear and free of burrs. Each batch is sampled for torque repeatability—we tighten and loosen the locking nut 50 times and confirm that clamping force variation stays within ±5%. This level of QC is standard, not an extra service. If you need to understand how our tolerances stack up against your application, read our CNC machining tolerances guide.
| Specification | Value |
|---|---|
| Shank Type | BT50 (ISO 7388/1) |
| Collet Type | ER32 |
| Tool Capacity | 1–20 mm (0.039–0.787 in) |
| Shank Material | 20CrMnTi forged alloy steel |
| Hardness (Taper & Nut) | 58–62 HRC |
| Case Depth | 0.8–1.2 mm |
| Taper Grade | AT3 (contact >90%) |
| Runout (TIR at 4×D) | ≤0.005 mm (0.0002 in) |
| Surface Finish (Bore & Taper) | Ra 0.4 µm |
| Coolant Pressure | Up to 50 bar (725 psi) |
| Lead Time (Standard) | 15 days |
| MOQ | No MOQ (single piece accepted) |
Standard ER32 chucks have a wall thickness of about 6 mm at the collet pocket. Our heavy duty version increases this to 9 mm. That extra 3 mm of steel adds 15% more radial stiffness, which directly reduces chatter in interrupted cuts. The locking nut uses a trapezoidal thread profile instead of a standard V-thread. This increases thread surface contact by 30%, allowing you to torque the nut higher without stripping.
We also balance every chuck to G2.5 at 10,000 RPM as standard. For high-speed machining above 12,000 RPM, we offer optional dynamic balancing to G2.5 at 20,000 RPM. This is not a marketing claim—every unit ships with a balance report. The heavier wall and larger nut also mean this chuck is heavier than standard versions, so check your tool changer capacity. Typical weight is 2.8 kg for a BT50 ER32 with a 60 mm projection.
We stock standard projections of 60 mm, 90 mm, and 120 mm. For special applications, we can machine custom lengths from 40 mm to 200 mm, but note that stiffness drops as length increases. We also offer coolant-through variants with a center tube that delivers coolant directly to the cutting edge—not just around the collet. This is essential for deep hole drilling where flood coolant cannot reach the flutes.
Custom options include modified taper angles, extended nuts for deeper pockets, and special coatings like TiN or AlTiN on the taper to reduce wear in high-insertion-cycle environments. Since we machine in-house, we can add your company logo or part number on the flange. There is no design fee for standard modifications like length changes or coolant ports. Just send your drawing and we will confirm the machining feasibility within 24 hours.
We have no MOQ—you can order a single piece for testing, and we will treat it with the same priority as a bulk order.
Yes, we machine custom lengths from 40 to 200 mm and offer center coolant-through tubes, with no design fee for standard modifications.
We use a CMM and a master BT50 gauge; runout is measured with a 10 mm test bar at 4× diameter, and taper contact is verified with blueing to >90%.
Standard sizes ship in 15 days; custom configurations take 25 days from drawing approval, and we provide a firm delivery date before you place the order.
Send us your drawing or your spindle specifications, and we will reply with a firm price, lead time, and a DFM (design for manufacturing) note if we see any issues. We are a 20-year-old precision manufacturing factory in Dongguan, China, with in-house CNC machining, stamping, springs, and heat sink production. All quotes are answered by an engineer, not a sales bot.
Email: sc@bquq.com
WhatsApp: +86 13713157787
Include your target runout, projection length, and if you need coolant-through. We will send a PDF drawing and a quotation table within 12 hours.
| 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 |
