CBN Insert Selection for HRC 55–65 Hardened Steel

UHD provides CBN insert selection guidance for batch finishing of hardened steel at HRC55-65, helping manufacturers balance grind-replacement hard turning surface quality with edge stability in continuous, light-interrupted, and heavy-interrupted cutting applications.

Batch machining of hardened steels such as GCr15, 20CrMnTi, 40Cr, 65Mn and Cr12MoV at HRC55–65 often requires two outcomes at once: surface quality suitable for hard turning instead of grinding, and reliable edge stability where keyways, oil holes, splines or other features create interrupted cuts.

UHD applies a condition-based selection path: first identify continuous, light-interrupted or heavy-interrupted cutting; then match insert structure and grade to the required wear resistance, toughness and precision target. The result is a practical starting point for gear shafts, bearing raceways, long shafts, precision tapers, grooves and ball screw raceways.

CBN insert machining hardened steel component

Hardened Steel CBN Insert Selection Table

The parameters below are reference starting points. Validate them against machine rigidity, clamping, tool overhang, coolant method, stock allowance and workpiece runout before production release.

Material Hardness	Typical Workpiece	Cutting Condition	Recommended UHD Insert Series + Grade	Vc (m/min)	f (mm/rev)	ap (mm)
Hardened steel (GCr15 / 20CrMnTi / 40Cr / 65Mn / Cr12MoV, HRC55–65)	Gear shaft journals, bearing ring raceways	Continuous finish turning (hard turning instead of grinding)	Coated CBN Insert → UPN601	120–200	0.05–0.12	0.1–0.3
	Gear tooth roots, shafts with oil holes / splines	Heavy interrupted cutting, rough / semi-finishing	Integral Brazed CBN Insert Series → USN650	70–120	0.10–0.25	0.3–1.5
	Interrupted finish turning with keyways or oil holes	Light interrupted finish turning	Full Face CBN Insert Series → UPN801	80–140	0.08–0.15	0.2–0.6
	Long shafts, piston rods, wind power main shafts	Long-distance continuous OD turning	Full Face CBN Insert Series → BN91	90–140	0.10–0.20	0.2–0.5
	Precision spindle tapers, high-end bearing raceways	Ultra-high precision machining	Solid CBN Insert Series → UBN S4	80–150	0.03–0.08	0.05–0.15
	Relief grooves and sealing grooves in hardened steel parts	Grooving and profiling	CBN Grooving Insert Series	60–120	0.05–0.12	One pass to groove width
	Ball screw thread raceways	High-speed hard whirling milling	CBN Whirling Insert Series for Ball Screws → UPN608S	200–400	0.05–0.15 (per tooth)	0.1–0.3

Implementation Priorities by Cutting Condition

Continuous Finish Turning

For grind-replacement hard turning, UPN601 supports a wear-focused approach. Use controlled cutting depth, stable tool-nose positioning and process checks for surface finish and dimensional drift.

Interrupted Cutting

UPN801 is suited to light interruption, while USN650 prioritizes impact resistance in heavy interruption. Before increasing speed, control runout, clamping rigidity and uneven stock.

Precision and Long Runs

UBN S4 is intended for demanding precision tasks; BN91 addresses long continuous OD cuts. Tool-life windows, thermal stability and workpiece support are key to repeatability.

Application Scope and Selection Inputs

This guidance is designed for hard turning, finishing and interrupted cutting of HRC55–65 hardened steel. It is not a primary selection guide for non-ferrous metals or austenitic stainless steels.

For a more reliable UHD trial recommendation, prepare the material grade and hardness range, operation stage, allowance, surface-finish or tolerance target, interruption details, machine capability, clamping method and current insert failure mode. This helps align the insert grade and initial Vc, f and ap window with the actual machining system.