Case Study: How We Boosted Car Inter-Shaft Hard Turning Tool Life by 67% with Custom CBN Inserts
In automotive transmission manufacturing, gear shaft hard turning (often called "grinding-to-turning"）has heavily replaced traditional grinding due to its high efficiency and lower equipment footprint. However, when continuous high-speed turning meets case-hardened steel at HRB/HRC 58–62, standard PCBN inserts frequently fail due to rapid thermal wear and micro-chipping.
Today, the application team at Zhuzhou Chuangde Cemented Carbide Co., Ltd. shares a real floor test from an automotive transmission component line. Here is how we re-engineered the tool geometry to crush a stubborn tool-life bottleneck on case-hardened inter-shafts.
The Application & The Floor Bottleneck
Our customer was finish-turning the two end cylindrical surfaces of a transmission inter-shaft.
Part: Transmission Inter-Shaft
Material: 20CrMnTiH (Carburized and Quenched Steel)
Hardness: HRC 58–62
Operation: High-precision, continuous hard turning
The Problem:
The operator was experiencing unpredictable micro-chipping on standard PCBN edges. Hard turning generates intense localized heat at the tool-workpiece interface. Without proper micro-geometry, the cutting edge experiences rapid thermal fatigue, leading to premature chipping. This caused surface roughness variations and dimensional drift, forcing the operator to constantly stop the machine for tool offsets and premature insert indexing.
The Solution: Edge Macro-Geometry Optimization
Instead of throwing a random harder grade at the problem, we looked closely at the micro-geometry. For rigid continuous turning on HRC 60 steel, the edge needs the perfect blend of sharpness and mass support. We customized a tipped-PCBN insert:
Insert Spec: DNGA150408-2S
Edge Preparation (The Game Changer): We applied a precise S-type chamfer (land + hone). The land width (T) was set to 0.12mm with a chamfer angle of 25°. This specific micro-geometry redirects the cutting forces away from the fragile tip into the massive body of the insert, preventing thermal micro-chipping without increasing cutting resistance excessively.
Cutting Parameters & Head-to-Head Test
We ran our custom insert head-to-head against the customer's incumbent PCBN insert (a well-known domestic brand) on the same CNC lathe, using identical parameters:
Practical Parameters:
Cutting Speed (V_c): 120 m/minDepth of Cut (a_p): 0.25 mmFeed Rate (f): 0.08 mm/rCooling: Wet (Standard emulsion)
Tool Life Result:
Brand | Tool Life (pcs/edge) | Output Increase |
Incumbent Brand PCBN | 300 pcs | Baseline |
Chuangde Custom PCBN | 500 pcs | 67% |
By jumping from 300 to 500 pieces per edge, the shop eliminated two insert indexing stops per shift. The floor reality of a 67% tool life increase is a direct 30% drop in overall tooling cost per component, combined with much tighter dimensional stability across the batch.
Get a Free Tooling Audit & Trial Insert
Are your cycle times dragged down by frequent tool offsets or chipping on case-hardened gears, shafts, or bearing raceways?
Stop overpaying for overpriced import brands. Work directly with a factory-direct technical partner who understands Total Cost of Ownership (TCO). Contact us today for a free edge optimization consultation or to request trial samples!
Email: info@cdcnctools.com
WhatsApp/Phone: +8613786352688
Address: Zhuzhou Cemented Carbide Industrial Zone, Hunan, China
