Most centreless grinding operations start life running conventional abrasive wheels - aluminium oxide or silicon carbide - because they are widely available, cost-effective and well understood. For many applications, that approach works perfectly well. But there are situations where conventional abrasives reach a performance ceiling, and where switching to CBN (Cubic Boron Nitride) grinding wheels can make a measurable difference to part quality, productivity and overall cost of grinding.

Understanding when that switch is justified - and when it is not - requires a clear look at what CBN offers, what it demands in return, and whether your application and machine setup are suited to it.

What Makes CBN Different

CBN is one of the hardest cutting materials available, second only to diamond. Unlike diamond, which breaks down at the temperatures generated when grinding ferrous materials, CBN is thermally stable and chemically resistant when cutting steel and cast iron. This makes it particularly suitable for grinding hardened steels, high-speed steels and superalloys - materials that are common in aerospace, automotive powertrain and medical device manufacturing.

The key characteristic of a CBN grinding wheel is its extremely low wear rate. A conventional abrasive wheel removes material from the workpiece but also wears progressively itself, changing its diameter and requiring regular dressing to restore its cutting action and profile. A CBN wheel, by contrast, holds its form and diameter for far longer. In applications where this matters - high-precision components, tight dimensional tolerances, or long production runs - this property has significant practical value.

Where CBN Wheels Deliver Results

CBN grinding wheels are not suited to every centreless grinding application, but there are specific situations where their advantages become compelling.

Hard and difficult materials. If you are grinding hardened tool steels, bearing steels or nickel-based alloys, conventional abrasives generate significant heat at the grinding interface and wear quickly. CBN maintains its cutting edge at high temperatures and cuts more efficiently through hard materials, reducing thermal damage to the workpiece surface.

High-volume production runs. When grinding the same component in large quantities, the dressing frequency required by conventional wheels introduces both downtime and dimensional variability. Because CBN holds its form between dressing cycles, process consistency across long runs improves significantly. Fewer interruptions mean more parts per shift and more stable size control throughout the batch.

Close-tolerance components. For parts where diameter tolerance is measured in microns rather than hundredths of a millimetre - as is common in medical device and aerospace work - the dimensional stability of a CBN wheel through a production run is a practical advantage. A conventional wheel that is gradually wearing changes the effective grinding diameter and requires compensation; a CBN wheel demands far less of this continuous adjustment.

Surface finish requirements. In applications where surface finish specification is demanding, the sharp, consistent cutting edges of CBN abrasive grains produce finer finishes with less surface damage than worn conventional abrasive. This is relevant for components such as precision pins, shafts and medical implant components where surface integrity is critical.

What CBN Requires from Your Process

Switching to CBN wheels is not a straightforward drop-in substitution. CBN technology demands more from the wider grinding system, and failures to account for this are the most common reason CBN trials underperform.

Machine rigidity. CBN wheels require a stiff, rigid machine to perform correctly. Any play in spindle bearings, slides or the work-rest blade system will prevent the wheel from cutting cleanly and will generate vibration that damages both the wheel and the part. Before specifying CBN wheels, machine condition needs to be assessed honestly. Spindle condition and bearing integrity are particularly important - issues that our machine servicing and spindle refurbishment capability can address before a CBN specification is committed to.

Coolant supply. CBN grinding requires effective coolant delivery at the grinding interface. Inadequate coolant flow, poor filtration or contaminated coolant will reduce wheel life and compromise surface finish. Coolant filter paper rolls should be checked and changed regularly to maintain coolant cleanliness in systems running CBN wheels.

Dressing discipline. While CBN wheels dress less frequently than conventional abrasives, dressing them correctly is more critical. Diamond dressing tools must be in good condition and correctly set up. Worn or incorrectly positioned diamond dressers will damage a CBN wheel surface or fail to condition it properly. Our diamond dresser reset service is worth considering as part of any transition to CBN to ensure dressing tools are fit for purpose.

Work-rest blade condition. Because CBN operations typically target tighter tolerances, the condition and geometry of work rest blades becomes more critical. Worn or incorrectly profiled workblades undermine the precision that CBN wheels are capable of delivering. This is an area where our workblade regrinding and refurbishment service, combined with blade material recommendations for your specific application, supports the overall process.

CBN Mounted Points and Internal Applications

Beyond grinding wheels, CBN is also available in the form of CBN mounted points - small, mounted abrasive tools used for internal features, slots and detailed grinding tasks that full wheels cannot reach. These offer the same advantages of hardness and thermal stability in a format suited to smaller, more complex features on precision components.

We supply both CBN grinding wheels and CBN diamond mounted points, and can advise on the appropriate specification for your material, component geometry and finish requirement.

Making the Decision

The decision to move to CBN should be driven by a clear business case - not simply by the appeal of newer technology. If your current process with conventional abrasive wheels is producing acceptable quality at acceptable cost, there may be no practical reason to change. CBN wheels carry a higher upfront cost, and the investment only makes sense where the benefits - longer dress intervals, improved consistency, better finish or reduced thermal damage - translate into real savings or quality improvements over the production run.

If your application involves hard or difficult-to-grind materials, close tolerances, high volumes or demanding surface finish specifications, the case is worth examining carefully. Our team can review your current process, materials and machine condition, and give you a practical assessment of whether CBN is likely to deliver a genuine return in your specific situation.

Get in touch with Workblades & Formers Ltd to discuss your grinding application and find out whether CBN wheel technology is the right next step.