Concrete cutoff saws

Concrete Construction, August, 2004

Hand-held concrete saws, often referred to as cutoff saws, come in several types. The most common is the circular or wheeled version, which is frequently gasoline powered. Concrete cutoff saws are considered by some to be, well, just plain unfriendly. But in the hands of a professional who needs to get a job done, their power and versatility often provide the key to success. Circular saws can be heavy, require regular maintenance, and can be very dangerous. Its spinning wheel creates gyroscopic forces, requiring the operator to use two hands and have sure footing. The concrete cutoff saw can act almost with a mind of its own, making it one of the most demanding tools to use; but it can cut just about anything. While choosing a cutoff saw often comes down to personal preference, understanding the tool can help you to make a purchase you'll be pleased with.

A few words of warning first: The diamond blade, commonly used on the cutoff saw, cuts differently than carbide blades, which work best on wood. Diamond blades cut by grinding the concrete, while carbide blades cut by chipping or tearing away at the wood. For that reason it is very important never to substitute a carbide blade for a diamond blade.

Features and benefits

Air filtration is a primary issue to consider when you buy a cutoff saw. Because of the grinding action, saws make clouds of dust when cutting dry concrete. So, although there are blades for wet and dry cutting, wet cutting has several advantages. It reduces the environmental hazard not just for the operator but also for those around the work area.

With dust suppression and air filtration, the saw lasts longer. Dust is the leading cause of shortening the tool's life. Dust or dirt entering the gasoline engine can destroy it quickly. Manufacturers have gone to great lengths to build in sophisticated air filtration systems, including multistage paper filters and oil-foam filters. It is important to change the air filters regularly, particularly when dry cutting.

Lighter saws seem to be the order of the day. Typical saws range from 20 to 35 pounds. However, lighter is not always better. It is important to let the tool do most of the work. So even though a lighter tool may be easier to carry around, it might actually make the work more difficult.

Buyers also have to consider other design features, including handle configuration, location of the spark plug, and how easy it is to change. Power is another consideration; but horsepower doesn't tell the whole story. It is torque that does the work, and that depends on the belt tensioner design. The best way to judge torque is to try out a machine.

Lastly, service is something to consider. With most machines, manufacturers frequently tout service as important, but it is more relevant in this case because of the amount of maintenance these tools require. Buying one without an adequate service network could possibly shorten its lifespan, costing more in the end.

Blades offer another source of variation. Blade makers and suppliers are more numerous than saw makers, and the range of blades is even wider. Diamond blades alone have a huge range of options. For example, Thomas Fisher of Diamond Products said his company has nine different blades for cutting cured concrete, from economical blades up to high quality and specialty blades.

The science of diamond saw blades is complicated. Important factors include diamond density and size and the quality of the bond that holds the diamond to the wheel.

Until recently there has been little to help consumers distinguish among blades types and qualities. The Concrete Sawing and Drilling Association is trying to cut through the confusion by establishing an application coding system for diamond blades. The system describes blades based upon the type of cutting (wet or dry), what is being cut (concrete, asphalt, tile, etc.), and with what kind of saw. While only voluntary for manufacturers, the code offers a first step for consumers to find what is right for them.

If you want to learn more about the new coding system, contact CSDA at www.csda.org. To learn more about any of the saws and blades listed below, circle the corresponding reader service card number.