In the late 1970s, Jay Halloran saw a need for change in the brush chipper knife industry. Halloran and Norval Morey (former owner of Morbark Industries), were co-owners of Michigan Knife. Until then, chipper knives had only one cutting edge, wasting space and the usefulness of the chipper knives. It was Halloran's idea to sharpen two edges, forever changing the brush chipper industry.

They developed their new company into one of the most respected chipper knife manufacturing operations in the nation. Shortly after inventing the double-bevel chipper knife, chippers started getting bigger and horsepower increased. The new double-beveled chipper knives started breaking, because their hardness was uniform. Michigan Knife began varying the hardness of their blades, making them soft in the middle and hard on the edges. By softening the middle, the chipper knives flexed at the higher impacts without breaking, while maintaining a hard cutting edge.

In the 1990s, the brush chipper knife industry went through more dramatic changes involving everything from one company buying out its competitor to leveraged buyouts from large venture capital firms. By the end of the decade, Halloran was owner of The Knifesource, which, along with Simonds Industries, are the major suppliers to chipper manufacturers and their dealers. Companies such as Zenith Cutter and Sharp Tool are major providers to the after-market business.

To make great chipper knives, you need to start with great steel. Steel's main ingredient is iron, about 85 percent. Carbon, phosphorus, sulfur, silicon, vanadium, manganese, molybdenum and chromium are added to make steel. The last three elements - especially chromium - are the most expensive, so cheaper steel will have less of these three materials.

Chipper knife manufacturers buy raw steel in hot rolled bars that are an oversized width and thickness. The metal comes with a slight overrun to allow for grinding to exact tolerances after heat treatment. In the first step of chipper knife production, a piece of steel is preheated to 1,100 degrees Fahrenheit, and is then put into a 1,960-degree oven. The metal is left at this temperature for 10 to 15 minutes. It is then taken out and brought down to 135 degrees.

As it cools, the metal goes to a Rockwell - a unit used to measure metal hardness - of 59 to 60. At that point, molecules in the metal are beginning to line up according to grain size, but at this hardness, if dropped, the metal would shatter like glass.

The blades are then put in a tempering oven at 960 degrees for six hours. This makes the metal grains tighten up, much like braiding a rope increases its strength. While tempering, the chipper knife Rockwell drops to between 54 and 56 - the preferred hardness for the edges but not the center of the chipper knife. The chipper knives are then double or triple tempered to give the metal grains another chance to line up and strengthen.

After tempering, the center around the holes is heated up (a process called annealing). This process is done in approximately 30 seconds and brings the Rockwell of the center to between 38 and 45. If the center is heated more slowly, the heat bleeds to the perimeter, softening the cutting edge. The softened middle allows the chipper knife to flex when cutting, reducing the chance of breakage. When heated, the blades are ground to their exact size and are ready for shipping.

Now you know how a great chipper knife is made. So how can you look at a chipper knife and tell if it is a good one or a bad one? You can't. There is no way a person can hold up two sharp chipper knives side by side and tell which one is better. What a person should do is check with the chipper knife's supplier. Since steel can be domestic or imported, you want to make sure your supplier has tight controls over the steel he buys and uses. Next, inquire about the percentage of elements in the steel. Chromium is vital, and good steel has a minimum of 7.25 percent chromium.

The only other way to tell who makes good chipper knives is through your own experience and information supplied through dealers and manufacturers. If your chipper knives are cracking or flaking easily, that's a sign of bad steel or a poorly heat-treated product. Since there are so many good chipper knife manufacturers, finding a competent source shouldn't be hard.

There are two ways to sell chipper knives: either direct to the end user like Zenith Cutter Co. and The Sharp Tool Co., or through a distributor such as Simonds Industries and The Knifesource.

Direct sellers market heavily and count on low prices and quick service to drive their business. "Our preference is to sell a high-quality product at a competitive price," explains Doug Long, the chipper product manager at Zenith. "We have a pulse on the industry by selling direct. It puts us in greater control of our destiny."

To put it another way, they prefer that the end user - and not a few large chipper manufacturers - directs their business. In addition, if a customer is particularly happy (or displeased), Zenith gets quick feedback. Paul Morrete of The Sharp Tool Co. agrees. "What separates us is our service … We try to make it easy for people to do business with us. People can call with a credit card, place an order before 3 p.m. and have it shipped the same day."

In this situation you can count on the dealer (usually a chipper dealer as well) to offer advice on the best chipper knife for each situation. "Since you can't tell a good chipper knife from a bad one by looking at them, our dealers give our customers the information they need," notes Ray Eluskie, the knife product manager at Simonds. "We do all our manufacturing in house, so people can count on quality."

Halloran at The Knifesource also makes everything in house. In the business for 40 years, he only sells to chipper manufacturers and their dealers and feels that the end user is best served that way.

Over the years, chipper knife production has improved. However, like many American industries, changes in the market have resulted in some problems that arborists should know about.

As long as most arborists get good quality chipper knives, few will ever notice, or even care, that the chipper knife industry has changed in recent years. Venture capitalists have moved into the industry, issuing bonds and using company assets as collateral to secure the debt. As a consequence of the debt, bond payments have been missed.

"The steel industry is not supporting the chipper knife manufacturers because bills aren't being paid properly," says Halloran at The Knifesource. "With some companies in financial difficulty, prices drop, and in the end this will hurt quality and supply."

As Halloran sees it, when a manufacturer gets into financial trouble, the company has to try anything to increase sales. This means lowering prices and quality. In the meantime, the other manufacturers lose contracts to the low pricing, and are forced to follow the same path in order to compete. It becomes a vicious cycle.

Since you can't tell a good blade from a bad one by looking at them, the best you can do is buy from a reputable company. In the world of chipper knives, quality matters, and you have to pay for it.