When sharpening woodturning tools, you want to make sure you have the right tool for the job. Successful sharpening depends on the method of grinding, tool setup, and using the right grinding wheel. Using a cubic boron nitride (CBN) grinding wheel is better than using silicon carbide or aluminum oxide. But how long does a CBN wheel typically last?
CBN wheel lifetime depends on your workload, but most experts say that with proper care, they will last a lifetime – up to 300 times longer than other wheels. Diamonds are the only harder surface, yet CBN will wear down over years of use. Still, a well-cared-for wheel will continue to grind.
But there are many opinions and claims as far as how long your CBN wheel will last. Much of it has to do with what you use it for and how often you use it. Let’s take a look at some of the specifics.
What to Use When Sharpening Your Tools
Sharpening your tools, like your chisels or scrapers, can be a daunting task if you do not have the right type of grinding wheel. If you have been using an aluminum oxide wheel to sharpen your tools until now, you may want to switch to a CBN wheel. They work better and last longer than any other material.
What is a CBN Wheel Made of?
CBN is made of cubic boron nitride, also known as Borazon, which is a combination of nitrogen and boron. It has a rating of 9 on the Mohs scale of hardness. In fact, the only material harder than CBN is the diamond, which has a hardness of 10 on the Mohs scale. CBN can be used on many materials, including:
- Titanium graphite
- Powdered metal
- Ferrites
- Zirconia aluminum oxide
- Tungsten carbide
- Tool steel
- Die steel
- Bearing steel
- Cast iron
What Makes CBN Last Longer than the Others?
It is not just that CBN is strong, it also has four times the abrasive resistance and 55 times higher thermal conductivity.
It does not generate a high heat because it conducts the heat better, dispersing it without harming the material you are working with.
This makes it the perfect wheel for grinding tools at high speeds since there is little or no damage to the tools.
This is also what makes it last longer than the others. Being second in hardness only to the diamond, CBN actually lasts longer because it does not wear away like diamond does.
The Types of CBN Wheels
There are several types of CBN wheels. The resin bond CBN wheels are best for cutter and tool grinding while the electroplated CBN wheels are good in form grinding.
The vitrified bonds are made of flux and superheated ground clay. It is an extremely strong bond. However, they are not good for rough work because of their rigidity. Organic bonds have better shock absorption.
What Are the Various Types of Grits?
All of the types of CBN wheels come in different grits as well. You may need more than one type of grit for your work, but if you are trying to get a sharp edge, start with a 180 grit. The most common seven grits include:
- 60 grit is best for profiling
- 80 grit is good for beveling
- 180 grit is great for raising burrs and sharpening scrapers
- 220 grit is best for sharpening
- 350 grit leaves a very sharp edge
- 600 grit is used for an even sharper edge
- 1,000 grit is used when you need a razor-sharp finish
What Are Other Grinding Wheels Made of?
There are five main types of abrasives on grinding wheels. Some of the most common abrasives used in grinding include:
- Ceramic is a five or six on the Mohs scale of hardness
- Aluminum oxide is a nine on the Mohs scale of hardness
- Silicon carbide is between a nine and 10 on the Mohs scale of hardness
- CBN is between a nine and 10 on the Mohs scale of hardness
- Diamond is the hardest material and is a 10 on the Mohs scale of hardness
Although diamond is the hardest material, it is not typically used instead of CBN wheels because the CBN crystals have better chemical and thermal resistance. Diamond crystals also end up flat because they microfracture instead of microchipping like CBN crystals.
Diamond wheels are better for honing while CBN is best for grinding.
There Are Even Different Shapes of Grinding Wheels
Another factor in grinding wheels is the shape you choose. The choice you make depends on what type of grinding you will be doing. There are six shapes in grinding wheels. These include:
- Straight grinding wheels. These are the most basic and are commonly used for lawnmower blades and chisels
- Large diameter grinding wheels. These are the same as a straight grinding wheel but larger
- Grinding cup wheels are most often used to polish concrete or stone
- Grinding dish wheels are like cup wheels but are more shallow
- Segmented grinding wheels are used with lubricating and cooling fluids to grind large amounts of material fast
- Cutting face grinding wheels can be used for anything from shaping saw blades to cutting tile
If you are planning to use your CBN wheel for grinding a hard material of any kind, then CBN wheel grinders are the best for you. You can use the CBN wheel with water for wet grinding as well.
They do cost more than the aluminum oxide wheels but they last longer and do a better job on just about all materials. Your initial investment will bring a high return after a short time.
Other Benefits of the CBN Grinding Wheel
The CBN wheel is more stable under heat than other materials and has an excellent hardness and better chemical resistance than any other grinding abrasive.
From ceramic blades to high-speed steel, your CBN wheel will do the job in less time and will not damage the tool or the wheel. It gives a smaller burr and a sharper edge apex than the others as well.
The CBN grinding wheel comes already perfectly balanced so you do not have to worry about balancing it on your machine. That means it will never wobble and will always spin true. They come with a bushing that is machined to match your wheel with your grinder and there are no plastic parts. They do not break if you drop them and even if you overtighten them, they will not crack.
What You Cannot Do with a CBN Grinding Wheel
Because CBN is made for hardened steel, you should never use them for soft metals or substances. They do not do well with:
- Copper,
- Aluminum, or
- Any other soft metal because the pieces can clog the pores of the wheel.
- You should also not try to grind carbide with your CBN wheel.
You will need a diamond wheel for that. Also, do not use stamped steel flanges or store-bought washers on your wheel. They can cause it to wobble.
Making Your CBN Wheel Last a Lifetime
If you are mainly going to be using your CBN wheel to sharpen and hone your wood turning tools, your wheel should last you a lifetime.
Clean your wheel once in a while with Kroil lubricant or WD-40.
Make sure the wheel is off and scrub the surface with a steel brush or toothbrush.
As long as you take care of the wheel and do not use it on soft metals or materials, your CBN wheel will keep your tools sharp for as long as you need them.