How to Select Full-Face CBN Inserts for Hardened Steel Finishing

Henan UHD Ultrahard Tools Co., Ltd

2026-08-12

Industry Guide

UHD explains how to evaluate full-face CBN inserts for hardened steel finishing, including continuous and interrupted cutting conditions, grade and specification considerations, chipbreaker options, and application limits.

UHD full-face CBN insert for hardened steel finishing on a CNC turning application

For hardened steel finishing, insert selection should start with the actual cutting condition rather than insert shape alone. UHD full-face CBN inserts use a CBN-covered top surface and an indexable design intended to provide multiple usable cutting edges for stable batch machining under suitable conditions. Selection should consider the workpiece material and hardness, machining stage, cutting continuity, machine rigidity, required surface quality, and chip-control requirements.

What Is a Full-Face CBN Insert?

A full-face CBN insert is a turning insert with CBN material covering the top cutting surface. Compared with designs that use CBN only in a localized cutting area, the full-face structure can allow more edges to be used through indexing. For continuous batch finishing of hardened steel, this structure is intended to support consistent edge condition and more efficient insert utilization.

Primary application focus Full-face CBN inserts are generally considered for finishing and semi-finishing operations where stable machining, dimensional consistency, surface quality, and controlled edge wear are important.

A Practical Selection Framework

The following sequence helps purchasing teams, process engineers, and CNC turning operators assess whether a full-face CBN insert is appropriate for a hardened steel finishing operation.

Confirm the workpiece material and hardness. Identify the hardened steel grade, heat-treatment condition, and hardness range. Material information is necessary for selecting a suitable CBN grade and edge preparation.
Define the machining stage. Full-face CBN inserts are generally better aligned with semi-finishing and finishing than with heavy roughing. Confirm stock allowance, target tolerance, and surface-finish requirements before selection.
Classify the cutting condition. Distinguish continuous cutting from interrupted cutting. Mild interruption may require a different balance of wear resistance and edge toughness; severe impact interruption should be reviewed carefully.
Match insert geometry to the operation. Select the insert shape, size, corner radius, and clearance configuration according to the toolholder, component profile, access direction, and required cutting stability.
Review chip control and burr requirements. When chip evacuation, chip entanglement, or burr formation affects cycle stability, a custom chipbreaker may be considered within the available CBN layer and geometry design.
Validate on the machine. Stable clamping, suitable machine rigidity, and reasonable cutting parameters are important. Technical review and machining validation remain necessary before production release.

Key Factors in Hardened Steel Finishing

Selection Factor	Why It Matters	What to Review
Cutting continuity	Continuous cuts typically place priority on wear stability; interrupted cuts introduce additional edge-load considerations.	Continuous, mildly interrupted, or strongly interrupted cutting condition.
Machining allowance	Stock allowance affects edge loading and determines whether a finishing-oriented insert is suitable.	Depth of cut, machining stage, and whether the operation is semi-finishing or finishing.
Surface requirement	Surface quality goals influence grade, edge condition, corner radius, feed, and finishing strategy.	Target roughness, dimensional tolerance, and any subsequent grinding or polishing process.
Chip formation	Uncontrolled chips can affect workpiece quality, automation, and machining rhythm.	Chip length, chip evacuation path, burr condition, and need for a dedicated chipbreaker.
Machine and setup stability	CBN cutting performance depends on stable clamping and controlled vibration.	Machine rigidity, holder overhang, workholding, runout, and process repeatability.

Selecting for Continuous vs. Interrupted Cutting

Continuous finishing

For stable, continuous hardened steel finishing, selection commonly focuses on wear resistance, edge consistency, and the ability to maintain dimensional and surface-quality stability over repeated cycles.

Confirm a stable finishing allowance.
Match insert geometry to the component profile.
Review edge wear and surface trend during validation.

Interrupted cutting

Interrupted conditions impose repeated impact on the cutting edge. Mild interruption requires careful grade and geometry review, while strong or severe impact interruption may exceed the intended boundary of a finishing-oriented full-face CBN insert.

Identify keyways, holes, splines, or other interruptions.
Evaluate impact level before production use.
Confirm suitability through technical review and trial machining.

Chipbreaker and Geometry Considerations

A full-face CBN structure provides space for chipbreaker design by pressing or grinding, subject to the selected insert configuration. A chipbreaker should be evaluated as part of the complete cutting system—not as an isolated feature—because chip behavior is also affected by workpiece material, feed, depth of cut, coolant strategy, and tool path.

When to consider a custom chipbreaker: persistent chip entanglement, unstable chip evacuation, burr-control concerns, automated production requirements, or a component geometry that needs a more controlled chip flow direction.

Available Full-Face CBN Grade References

UHD provides full-face CBN grades for defined applications. Grade selection must be based on the actual workpiece material and cutting condition. The grade references below are specified for cast iron applications and should not be treated as a substitute for hardened steel application review.

Grade	Key Characteristics	Applicable Cutting Condition	Specified Workpiece Materials
UPN801	Wear resistance and impact resistance	Low-speed interrupted turning or milling; roughing and semi-finishing	Alloy cast iron, gray cast iron, ductile cast iron
BN91	Wear resistance and heat resistance	High-speed continuous cutting; semi-finishing and finishing	Alloy cast iron, gray cast iron, ductile cast iron

Standard Insert Specifications

The following full-face CBN insert specifications are available in the listed UPN801 and BN91 grades. For hardened steel finishing, final configuration should be confirmed according to the application requirements.

ISO Specification	L (mm)	IC / Diameter (mm)	S (mm)	Corner Radius R (mm)
CCGW060204-Q	6.35	6.35	2.38	0.4
SCGN120404-Q	12.7	12.7	4.76	0.4
DNGN070204-Q	6.35	6.35	2.38	0.4
DCGW070204-Q	6.35	6.35	2.38	0.4
TNGN080204-Q	8	4.76	2.38	0.4
RNGN050400-Q	5	5	4.76	—

Specifications not listed above can be discussed with UHD for application-based review.

Application Boundaries to Review Before Ordering

Full-face CBN inserts are not a universal solution for every hard-material operation. To reduce the risk of edge chipping or CBN-layer damage, review the process boundary carefully.

They are generally not intended for heavy stock removal or severe impact interrupted cutting.
They should not be selected for non-ferrous metals or austenitic stainless steels.
For materials and conditions outside the confirmed application range, obtain technical guidance and validate the machining process before volume production.

Information for a More Accurate UHD Recommendation

Henan UHD Ultrahard Tools Co., Ltd can support standard insert supply, non-standard configurations, dedicated formed tools, and chipbreaker discussion. Providing complete process information helps align the insert solution with the actual machining objective.

Workpiece material and hardness Continuous or interrupted cutting Roughing, semi-finishing, or finishing stage Target tolerance and surface requirement Current insert life and failure mode Machine, holder, and clamping details

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