Circular saws cut new territory

Circular saw blades aren’t just for wood anymore. With purpose-built blades, they can also tackle metal.

by Clair David Urbain

The first thing my dad taught me about using a circular saw was to keep it out of the dirt and away from metal or any body part.

His sage advice still applies about the dirt and body parts, but with the right saw and blade, you can get through ferrous and non-ferrous metal as fast as a sugar addict can chew through hard candy.

But the news in circular saws isn’t all about metal cutting. There have been advances in wood cutting blades that make them cut faster and last longer. Circular saw experts share their observations about the new territory circular blades and saws are carving for themselves. They even offer some common – and uncommon – sense use tips that can help these blades do their jobs faster and more safely.

Wood cutting
Blade costs continue to decrease for commodity wood-cutting circular blades, report the experts. “Wood cutting is now a value proposition. Users can get great blade prices when they buy in bulk. The volume discounts yield lower costs,” says Shawn Horan, group product manager for accessories at Milwaukee Electric Tool.

But even with the lower costs of commodity blades, manufacturers continue to improve on well-proven designs, says Brad McMullen, DeWalt senior product manager of saw blades.

“The most recent advance that has spurred user interest is new blade coatings. They reduce friction and heat, which means less wear and longer blade life. A coating can also reduce pitch buildup and gumming when cutting manufactured wood or wet lumber,” McMullen says.

For general framing work, the most common blade used is the 7 1/4" diameter 24-tooth blade with carbide teeth, says Steve Phillips, blade and accessories product manager at PrimeSource Building Products, which recently introduced its own Grip-Rite blade line.

“As we develop our blade line, we are benchmarking popular blade types and changing a few things. Our first blade is the 24-tooth wood cutting blade. It meets the needs of framers and represents a large percentage of the market. We are working on blades that decrease wobble and increase cutting speed. We are focused on carbide quality and making sure our tips are welded properly to ensure they won’t separate from the blade,” he says.

Irwin has taken blade development to a different level with a patented tooth configuration on its Marathon blade. The blade has varying tooth widths that produce faster cuts with less effort when compared with a thin-kerf blade. “This gives us 20 percent faster cutting vs. the previous design without sacrificing durability. The first tooth cuts, then the second tooth cuts and cleans up the wood edge,” says Lisa Rizzo, Irwin circular saw blade product manager.

“The expansion slot configuration on the new Marathon blade prevents blade warping on cross, rip and radius cuts. The heat vents help with plate deflection and binding on deep cuts. By optimizing the expansion slot and heat vent design, tougher cuts through thick materials and difficult arch cuts are easier to make,” she says.

“The 7 1/4" diameter, 24-tooth blades are a commodity, and one with a thin kerf and hard body will work well in most framing applications. In some cases, opening price point or inexpensive blades are a good choice,” says Chris Carlson, Bosch Power Tool and Accessory saw blade product manager.

“However, higher cost blades offer lots of advantages. They are often coated, have better carbide and use better brazing processes that attach the carbide to the blade. Look at your applications. We recommend an inexpensive blade for form work or for a short-duration job where the blade may hit nails. There are various quality blades at that level,” says Rick Gray, saw product manager at Bosch Power Tools and Accessories.

Anti-kickback is another subtle difference users will find with brands and price points of blades. “For example, the plate of our Construction blade has an anti-kickback design. It has a pall behind the tooth that helps control feed which helps reduce kickback,” says Carlson. “Some blades have anti-vibration slots, which are laser-cut squiggles in the plate. “Some contractors like them, while others don’t. It creates some flex in the blade, but it can reduce vibration and noise,” he adds.

The experts report that the lower the blade’s tooth count, the faster and rougher the cut will be. Carlson recommends an 18-tooth blade for bevel cuts at 50 or 60 degrees. “You can also get a higher quality cut with a fewer-tooth blade by cutting slower,” he adds.

“Tooth angle can also affect blade cutting speed,” says Gray. “With the short cuts used in stud work, a 10 to 15 percent faster cut is something a user can’t really perceive. What counts to these types of users is blade durability. Changing out a blade in the middle of a job is time consuming,” he says.

“We are also seeing lots of interest in our nail cutter or remodeling blade,” says Carlson. “It has a low hook angle and a reinforced tip that can take abuse. The low hook angle helps them chew or chisel through nails,” he says.

Wood cutting with cordless saws
Cordless circular saws are gaining in power and popularity, but still haven’t replaced corded saws for high production jobs. Instead, these saws are most popular with trades that do punchlist work or utility jobs that would take more time stretching an extension cord than the time it takes to make the cut.

“Cordless saw blades have a thinner kerf. They remove less wood so there is less drain on the tool and therefore more run time. There are different tooth angle grinds that also help battery run time. There may be a slight trade-off on the finish of the cut,” says McMullen.

“Cordless saws have created an interest in using thin kerf blades in corded saws,” says Carlson. “The first cordless saws used thin kerf blades because it helped improve the number of cuts per charge. Users quickly saw the advantage of cutting faster, so they are moving toward thin kerf blades with corded tools. The new thin kerf blades are also hardened. They remove less material and cut faster. This was very important on early cordless saws.”

“The cordless blade development that’s now underway is due to the increase in power of the Litheon Li-ion battery system. The power is now there to cut. Just as in jigsaws and planers, the new cordless circular saws work as well as their corded counterparts. It really expands the usefulness of the tool,” says Gray.

What’s next for wood-cutting circular saw blades? “Some of the innovations found in metal cutting may be applied to wood cutting in the next few years,” says Horan.

Metal cutting
The advances in metal-cutting saws and blades is perhaps one of the fastest growing segments in the world of sawing.

“Intuitively, cutting metal with a circular saw isn’t something you’d expect to be able to do,” says Peg Thomas, accessories product manager at Milwaukee Electric Tool. “Over the past three years, there have been continual improvements to the technology.”

The new saws are capable of cutting ferrous and non-ferrous materials. “There are different metal cutting blades for different metals – aluminum, stainless steel and steel,” says Alan Peterson, product manager at The M. K. Morse Co.

“We have steel and thin steel blades. The thin steel blades are for material 1/8" thick or less. They have more carbide tips and produce a finer edge. They can cut thicker steel, but the cut will be slower and blade life will be shorter. These blade are more expensive than the steel cutting blades, so cutting thicker material with the thin steel cutting blade will cost you more per cut in time and in shorter blade life,” says David Byrley, director of new product development at The M. K. Morse Co.

“The thickness of the steel that can be cut is driven more by the power of the saw than the design of the blade. The blade for a conventional circular saw can cut steel up to 3/8" thick easily as long as it is under RC 25,” says Peterson.

Metal saw selection
The experts recommend using a purpose-built circular saw for cutting metal. “Although conventional circular saws can be used with some blades, we recommend using a special saw for high-volume cutting. Metal-cutting circular saws have a lower rpm and higher torque so the power curve is flatter. These special metal-cutting saws start at a lower rpm and then stay there throughout the cut,” says Peterson. “They also have a catch tray for metal chips, are more comfortable to use and are built to make repetitive cuts.”

Carlson also believes it’s better to use a saw built for metal cutting. “Cutting metal with a wood saw subjects it to ingesting metal chips, which can dramatically shorten the saw’s life.

Different design approaches
“Metal cutting blade design is evolving,” says Thomas. “They are so much more efficient than cutting with an abrasive blade or wheel. They offer a nice finished edge that’s cool to the touch and can be handled right after the cut without burning the skin. The cost per cut is low due to the fast cutting time and the more cuts per blade.”

David Serdynski, associate product manager at Milwaukee Electric Tool, encourages using metal-cutting saws. “They have the proper guarding and power for the job,” he says. “The blades in metal cutting saws also run slower than wood cutting saws. Metal cutting saws run at 3,500 rpm, where wood saws cut at 4,800 rpm. Metal-cutting saws also have a chip collector that reduces chips going everywhere and reduces cleanup time. It also offers a clear line of sight for the cut, adds Serdynski.

The one downside: Metal cutting blades are noisy. “We are trying to engineer out some of the noise. Users should wear hearing protection,” suggests Carlson.

“There is a difference between ferrous and non-ferrous metal cutting, so it’s important to know what you are working with. Use a magnet to see if the material has any iron in it,” suggests Jessica Jatczak, accessories senior product manager at Milwaukee Electric Tool.

Then, measure material thickness. That also affects blade selection, says Jatczak. Finally, will you be using a corded or cordless tool?

Nonferrous cutting
“Nonferrous blades are more aggressive than ferrous blades. They have a deeper gullet. However, it’s hard to generalize on metal-cutting blades because manufacturers approach blade design differently. So it’s best to refer to the application and cutting depth written on the blade to select the right blade for your job,” says Thomas.

Peterson says there has been huge growth in cordless blade sales. “Workers like the cordless tools while working on rolling scaffolds. Electricians like them for cutting conduit and light structural steel. The limit is the staying power of the tool. For many workers, it’s a good tradeoff not to deal with extension cords.”

Larger (14" diameter) blades can cut up to 5" diameter pipe. “These are special machines for this task,” says Peterson. “They cut at a lower rpm. The 10" or 12" chop saws for abrasive wheels or wood cutting blades or abrasive wheels run too fast to power a metal-cutting blade, so don’t mount metal-cutting blades to these machines.”

Published in the January/February 2007 issue of Contractor Tools and Supplies magazine.

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