Raising the Cutting Edge

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This article is from Issue 3 of Woodcraft Magazine.

When it comes to long-lasting sharpness, it’s hard to beat carbide. But a new generation of ceramic saw blades is stepping forward to challenge carbide’s dominance. Here’s a preview of what you might be using before long.

By John English

CARBIDE TECHNOLOGY has been a boon to woodworking. The characteristics of carbide cutting edges on saws, router bits and other equipment has meant sharper cutting, longer-lasting sharpness, and easier resharpening. Upgrading from all-steel to carbide has almost been the ultimate no-brainer.

But when it comes to the ultimate cutting edge, there might just be something even better.

Welcome cermets

They’re called “cermets,” a name the industrial world has given to a combination of ceramics and metal. Cermet-tipped blades are different than carbide in that they are designed to run fast and hard. They really start working well at the point where carbide performance drops off – when you’re feeding a lot of hardwood into your table saw, and the blade and the material are heating up. 

Cermet tips simply don’t do that. They stay a lot cooler and consequently retain their edge a whole lot longer. They have been tested rigorously in manufacturing settings, and the results show a huge increase in the amount of material the saw can handle, plus considerably less downtime changing blades. 

The bottom line

Cermet-tipped blades are only available in custom runs, and not from very many sources at that. According to Carbide Processors, Inc., a leading manufacturer of cermet-tipped circular saw blades, it could take months to deliver an order, since they must wait for enough to justify a manufacturing run. While serious woodworkers are definitely beginning to discover the benefits of cermet, everything is still custom. Current customers are enjoying four times the performance and five times the life of their carbide-tipped blades, so they’re willing to wait a few weeks for delivery. 

Cermet-tipped blades are surprisingly inexpensive. As of December 2004, Carbide Processors was offering standard 10" industrial quality blades in tooth counts of 24, 40, 60 and 80. Prices range from $150 for the 24-tooth blade, to $229 for the 80-tooth.

Blades with cermet tips typically require about one-third fewer teeth to do the same job better than carbide, which helps control costs. For example, 60-tooth top-of-the-line commercial blades cost about $110 apiece. By replacing them with 40-tooth cermet-tipped blades, your initial investment is only about 50 percent higher, and the lifespan of the blade is about five times longer.

Tom Walz, president of Carbide Processors, estimates a dramatic drop in price as production increases. 

EACH TIP on this cermet blade is a solid piece of the ceramic material used to coat standard carbide blades. Note that the tips are bigger than most carbide tips to allow for several sharpenings.

IN USE, CERMET-TIPPED blades can take a higher feed rate. The newly exposed grain of the crosscut piece of oak is cut almost to a polish.

TO DATE, most cermet blades have appeared in industrial applications, such as this Hula cutoff saw.

Well-tested technology

Cermets and ceramics have already replaced standard tungsten carbide in about 60 percent of all industrial metalworking applications. Carbide came to woodworking from metalworking, and now cermets and ceramics are following the same path to our workshops. The cermet used to create the tips on woodworking blades is made from titanium carbonitride (TiCN), a combination of titanium carbide and titanium nitride. Those are the same materials used to coat ordinary grades of carbide to make them more wear resistant. 

A cermet tip isn’t just coated with the material – it’s a solid chunk of the material. Although the U.S. Patent Office accepts this as a ceramic, it is in fact an intermediate grade that lies somewhere between tungsten carbide and true ceramics such as alumina, silicon carbide and zirconia. It has a lot of the positive qualities of true ceramics.

How the blades are made

Each saw blade starts out as a very flat, blank plate that has been carefully heat-treated to achieve the proper level of hardness without brittleness. After heat treating, the plates are inspected and reflattened if necessary, as absolute flatness is required to position the teeth properly and grind them to tolerances of less than 1/1000”. 

Each plate is then laser-cut, and notches are individually ground out to remove the heat-affected zones. The notches are carefully cut to leave the surface rough enough for a strong, consistent braze when the tips are attached.

Carbide Processors’ brazing procedure holds the teeth with greater tensile strength, and creates a suspension effect. This slight “give” reduces the impact on the cutters, just as a car’s suspension reduces shock. Manganese is also added to the brazing compound to strengthen the joint, reducing tip loss and breakage.

Then, the tips are ground. Cermet is more wear-resistant than carbide, so it is harder to grind and a different set of diamond wheels is required. If standard carbide wheels are used to grind cermets, they’ll do the job but there will be a huge amount of rubbing action and a lot of heat that will thermally stress the cermets. That’s why the company asks that blades be returned to them for sharpening.

Looking ahead

Over the next few years, ceramics might largely replace tungsten carbide, much as tungsten carbide has largely replaced steel. Currently the objections are the price of the material, and the fact that it is hard to make and hard to use. You also hear objections that there’s no market for it yet and there are few machines that can take advantage of all its benefits. Many of these reasons are identical to those used 30 years ago to explain why carbide couldn’t work.

Currently, cermet saw blades and tools are being developed by some of the largest saw companies in the world, and they’re being used successfully in more and more applications all the time. Like digital replacing analog in our lives, or lasers replacing levels, it’s just a matter of time before ceramics replace almost every other cutting material. And this time around, woodworkers are leading the charge.

For more information, contact Carbide Processors at (800) 346-8274. worldsbestsawblades.com

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