What This ER Collet Chuck Extension Bar Does for Deep Cavity Work This is a CNC machined ER collet chuck extension bar long reach CNC tool holder. It extends your tool’s reach by 50 to 150 mm withou
Get a quote
-
English
- sc@bquq.com
What This ER Collet Chuck Extension Bar Does for Deep Cavity Work This is a CNC machined ER collet chuck extension bar long reach CNC tool holder. It extends your tool’s reach by 50 to 150 mm withou
This is a CNC machined ER collet chuck extension bar long reach CNC tool holder. It extends your tool’s reach by 50 to 150 mm without adding a separate extension piece. Runout is held under 0.005 mm at the nose. Hardness is 58–62 HRC after heat treatment. Lead time for standard sizes is 7 days, for custom lengths 10–12 days.
Standard collet chucks vibrate when the tool sticks out more than 3x its diameter. Our extension bar shifts the gripping point forward. The shank is one solid piece from the taper to the collet nose — no threaded joints, no welded sections. This gives you a 40% stiffer assembly than a chuck plus extension adapter. You can run speeds up to 8,000 RPM with stable cutting in 5D cavities and deep rib slots.
We start with 42CrMo4 alloy steel or 20CrMnTi for case-hardened versions. After CNC turning and milling, we carburize or induction harden the gripping zone. Final hardness is 58–62 HRC on the collet taper and 50–55 HRC on the body. Surface finish on the taper is Ra 0.4 µm. This prevents galling when you clamp and unclamp ER collets hundreds of times per day.
We machine these extension bars in four standard collet sizes. ER11 for tool diameters 1–7 mm, ER16 for 1–10 mm, ER25 for 1–16 mm, ER32 for 2–20 mm. Shank options are straight cylindrical (Ø20, Ø25, Ø32 mm) or SK30/SK40/SK50 taper for direct spindle mount. Reach lengths from 50 mm to 150 mm in 10 mm steps. If you need a non-standard length, we cut it from solid bar — no extra tooling cost.
| Specification | Value |
|---|---|
| Collet Size (ER series) | ER11 / ER16 / ER25 / ER32 |
| Reach Length (extension bar) | 50 mm – 150 mm (custom up to 200 mm) |
| Shank Diameter | Ø20 / Ø25 / Ø32 mm or SK30 / SK40 / SK50 |
| Material | 42CrMo4 or 20CrMnTi (case-hardened) |
| Hardness (collet taper) | 58 – 62 HRC |
| Hardness (body) | 50 – 55 HRC |
| Runout (TIR at nose) | ≤ 0.005 mm |
| Surface Finish (taper) | Ra 0.4 µm |
| Concentricity (collet seat to shank) | ≤ 0.008 mm |
| Lead Time (standard sizes) | 7 days |
| MOQ | No MOQ (1 piece accepted) |
Every single extension bar is checked, not one per batch. We measure taper angle with a CMM (coordinate measuring machine) at 3 points. Runout is verified on a precision mandrel with a 0.001 mm dial indicator. Hardness is spot-checked on both the taper and body using a Rockwell tester. We send the inspection report with your shipment — PDF and photo of the actual part.
If your spindle runs above 8,000 RPM, order the G2.5 balancing option. We dynamically balance the assembled chuck (body + collet nut) at 15,000 RPM. The balance grade is G2.5 per ISO 1940. We also offer pre-set tool length offset — we measure the stick-out from the collet nose and engrave the value on the shank. This saves you 3–5 minutes per tool change on the machine.
A welded extension has a heat-affected zone that softens the steel. A screwed extension has threads that create micro-movement under load. Our bar is machined from a single forging. There is no joint, no weld bead, no thread gap. The collet taper is ground in the same setup as the shank, so the two axes are true to each other. That is why we hold 0.005 mm runout without adjustment.
No MOQ – we accept one piece for prototype testing or emergency replacement.
Yes, any length between 50 mm and 200 mm, and any shank diameter from Ø16 to Ø40 mm, with no custom tooling fees.
We measure TIR on a 100 mm test bar clamped in the collet, with a 0.001 mm dial indicator, and include the reading in the inspection report.
Standard sizes ship in 7 days, custom lengths in 10–12 days, and orders with balancing option add 2 days.
We know you need a part that fits your spindle and your pocket. Email your drawing or a simple sketch with your ER size, reach length, and shank type to sc@bquq.com. You get a firm price and a delivery date within 12 hours (working days). For urgent questions, WhatsApp +86 13713157787. If you are still deciding between tool holder types, read our CNC cutting tool selection guide. For tolerance questions on the shank or collet seat, check our CNC machining tolerances guide.
This is precision manufacturing, made in China, with no MOQ and no middleman. We are the factory — 20 years in Dongguan, CNC machining plus stamping and springs. You talk to the engineer who will quote your part, not a sales rep.
| 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 |
