Mount a dull steel blade on a new, $400 circular saw, and the professional-grade tool will slowly chop a ragged cut, and probably leave burn marks on the wood from excessive friction. But mount a new, top-line carbide blade on a $35 entry-level saw, and the cut will be clean and smooth.
It would be nice to have the best of both. But with saws, the extra investment can cost hundreds, and return power and durability for daily, contractor-grade production cutting that DIYers don't need.
With blades, the extra investment is often about $10, say for a Freud 71/4-inch blade with 60 carbide-tipped teeth — about $25 to produce a cut edge as slick as glass.
Die-hard woodworkers can debate the benefits of tooth angles and C3 carbide versus C4, the hardest on the market. But for most DIY work around the house, and even big projects, there are two basic blade materials, steel and carbide, and two basic configurations, crosscut and trim. Specialty blades for cutting plastics, concrete and other materials are mainly for contractors.
Steel vs. carbide
Steel is the old standard, largely replaced now by blades with carbide cutters mounted at the teeth. They're not sharper than steel teeth. They just stay sharp longer — up to 50 or 60 times longer. But steel has one big advantage: It's easy to touch up. Nick a nail, dull the blade cutting through hardwood knots, and you can sharpen the teeth on the spot with a metal file. DIYers and even most contractors don't have the specialized equipment or expertise to grind carbide teeth.
Carbide blades outsell steel by 8 to 1. But if you use a saw only a few times a year to cut some shelves, steel is fine. If you do more woodworking and use a carbide blade to cut material like veneer plywood, it's still handy to have a steel blade to use on rough jobs like cutting landscape timbers or old flooring that might contain hidden nails.
Prices rise with the blade diameter, but even more with the number of teeth. There are dozens of special features, like anti-friction coatings and expansion slots to disperse heat. But tooth count is the overall yardstick. A blade with fewer teeth makes less contact with the wood and produces a rougher but quicker cut. A blade with more teeth makes more contact and produces a finer but slower cut.
Crosscut blade: Most people use a crosscut blade (also called a combination blade) most of the time. For a standard, 71/4-inch circular saw, this all-purpose blade will have at least 24 teeth, and up to 40 when the manufacturer tags it as a smooth-cut combo blade. It's just right for cutting deck planks, fence posts and other beefy boards.
Trim blades: Generally have 40 or more teeth. They're best for cutting shelving, veneer plywood and other thinner lumber that requires finer, cabinet-quality joints. If you buy one blade, buy a combo, and if you're trimming finished lumber, move the saw more slowly than you would slicing a deck board to length.
Carbide.com offers an interesting selection process for choosing just the right blade for the job at hand. Once you have zeroed in on the most practical type of blade, or two, consider one with a coating, often Teflon, over the main blade plate that reduces friction and resists corrosion. If you're using a somewhat underpowered saw, or an older battery-powered model, consider a thin-kerf blade. It's slightly narrower than standard blades that typically make a 1/8-inch slot as they cut. Because the narrower teeth contact less wood, there's less strain on the motor and more power delivered as you make the cut.