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A Comprehensive Guide to CBN Grinding Wheels

How often do you go to sharpen a tool and find you need to replace your diamond grinding wheel? Does it feel like it’s too often?

It could be that you use your wheel more than most, but what if it is isn’t? You may simply not have the right wheel for the job, which can cause your grinding surface to wear out faster. 

Many think diamonds are the best grinding material due to their hardness, but that is not always true. It’s possible you’ll be better off using CBN grinding wheels. Under many circumstances, they last longer and can save you money over time through fewer replacements. 

Read on to learn why a CBN wheel may be a better option for your operation.  

How to Select a Grinding Wheel 

What you need to grind should be at the center of your wheel selection process at all times. Outside of that, there are three major aspects to consider when choosing a grinding wheel: 

  1. The abrasive material that allows your grinding wheel to do its job
  2. The bond that adheres the abrasive granules to the wheel
  3. The concentration ratio of abrasive granules bonded to the wheel

It is possible to tailor grinders to suit your specific purposes by adjusting each of these factors. Remember: the best abrasives, bonds, and concentration ratios for your needs all depend on what you intend to grind. 

Abrasive Granules

There is a wide variety of abrasives used on grinding wheels. These materials are broken into very small grains and adhered to the wheel with a bond. 

As you use the grinding wheel, small pieces of the granules chip off. This chipping effect keeps the grinding face of your wheel continually sharp. 

CBN Grinding Wheels

A CBN grinding wheel uses Cubic Boron Nitride, or CBN, as its grinding material. Cubic Boron Nitride is considered a super abrasive. As the name suggests, super abrasives are stronger than normal abrasives like Aluminum Oxide and Silicon Carbide. 

CBN is best used to grind hard metals like:

  • Steels with a hardness rating of at least 45Rc
  • Cast and wrought irons
  • Nickel alloys 

It is second in hardness only to diamonds. 

CBN Versus Diamonds

You may find yourself wondering why you would use a CBN grinding wheel if diamonds are harder. The simple answer is that when it comes to hard metals, diamonds aren’t built for the task. Diamonds are better for grinding more delicate items like glass, quartz, and ceramics.  

CBN doesn’t chemically react with iron. This lack of reaction allows CBN to remove more material and last longer than diamonds when grinding most hard metals.

A longer life cycle for your grinding wheel has several advantages: 

  • Fewer wheel changes
  • Less downtime
  • Lower maintenance costs
  • More controlled wear rates resulting in better wheel performance

CBN is also better than diamonds for grinding hard metals because it has a very high rate of thermal conductivity. It can with stand temperatures up to 1,000 degrees Celsius before it starts to degrade.

Even diamonds have a lower thermal conductivity than CBN and it is the best natural conductor of heat.

CBN Versus Conventional Abrasives

It is possible to grind hard metals with conventional abrasives, but the wheel won’t last very long. For this reason, a CBN grinder is usually a better fit.

Consider some of these benefits of using CBN over abrasive grains made of materials like ceramic or silicon carbide. 

  • Longer life expectancy
  • Better consistency
  • Flawless cutting edges
  • Less likely to burn or otherwise damage work

CBN’s high thermal conductivity rate helps out here too. It is why this material can promise less damage while grinding.  

The Bond

The adhesive bond on a grinding wheel doesn’t just hold the granules in place. It also acts as a shock absorber and helps maintain consistent wear on the grinding face. 

The two most common type of bond used with CBN grains is organic resin and vitrified bonds. 

Organic Resin Bonds

Organic bonds use natural materials that bind abrasive granules to a grinding wheel. Organic bonds are better shock absorbers than vitrified and metal bonds. Resin-based bonds are the most common organic bond when it comes to CBN grinding wheels. 

Of the available organic bonds, resin is the best at absorbing shock. When you combine CBN grains with a resin bond, you get a wheel that can remove large volumes of stock in a single go.

This type of wheel is perfect for rough work like conditioning hard metals or using abrasive cuts to remove entire pieces of steel. You can also combine resin and CBN for precision work like grinding diamonds. 

It is possible to do the same work with a different kind of bond, but shock causes the bond to break down faster. When the bond breaks down too fast, you get uneven wear and end up sacrificing wheel durability. 

If you would like to learn about the differences between CBN and Diamond resin wheels, read this article. 

Vitrified Bonds

Superheated ground clay and flux are the primary ingredients of a vitrified bond. Grinding wheels made with a vitrified bond are extremely strong, but rigid. This means that using them for rough work, as you would with a resin bond, is not a good idea. 

It is more common to find a vitrified bond with diamond grains than CBN, but this combination is still effective for grinding things like alloy steels. 

You may also consider a vitrified bond if water, oil or acid will come in contact with the wheel. These materials have very little effect on this type of bond.

The biggest benefit of a vitrified bond is that it can be redressed and reused when it wears down. This can save you a lot of money because you don’t have to replace wheels all the time. 

Concentration Ratio

The concentration ratio refers to the volume of abrasive granules to bond space on a grinding wheel. A high concentration ratio translates to a more efficient grind or G-ratio. 

With regard to CBN, you usually want the highest possible G-ratio. If you’re grinding softer materials, a lower ratio is more beneficial. 

An Action Superabrasive representative can help you figure out the perfect concentration ratio for your grinding needs. 

Need Further Guidance? 

This basic guide was hopefully enough to help you get a better idea of what you need for your grinding purpose. If you think a CBN grinding wheel may be the right fit for you, let us help you fine-tune your selection so you have the best tool for the job. 

Action Superabrasive is an ISO 9001 Certified company, so you know you will get the best quality products from us every time. 

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