Woodshops process a huge range of materials from composite boards and plastic laminates to solid lumber and foil. The machines that cut these run the gamut from beam saws to aggregate heads, so it’s challenging to set guidelines that work for all, or indeed even most, blades. The ideal solution is for a shop owner or manager to sit down with a tooling supplier and talk through all the options that apply specifically to the shop’s processes. And there’s a good chance the conversation would start with standard and thin kerf blades.
The reason that shops switch to thin blades is that in removing less waste (lowering the chip load) the blade is quite a bit easier on saw motors. A standard blade takes out a 1/8” wide kerf (0.125”), and a thin kerf blade is usually about 3/32” wide (0.09”), but some specialty blades such as the Micro-Kerf from Total Saw Solutions are much thinner than that (0.01”). The material savings that come with thin kerf blades are negligible unless the saw is running full-out for several hours a day. In the average custom shop, there’s no real benefit in terms of waste but in production shops with high volumes, there may be some savings. So, the huge advantage is that thin blades offer less resistance. That means the feed rate can increase a bit, which can save a little on labor costs. But shops generally switch because less resistance means less wear and tear.
The next most common saw blade question isn’t so much about the blade itself, but how it is used. Even experienced pros sometimes wonder if they’re setting the blade at its optimum height when ripping. It’s a good question. Conventional wisdom says to set the blade height on exposed cuts (as opposed to buried ones where the material is thicker than the depth of cut) so the bottom of each gullet just clears the material. The thought here is that the least amount of tooth exposure is safer for the operator, but the gullets still need to clear the material so they can dissipate waste from the cut.
For the occasional hobby woodworker, that’s probably a sound theory. For professionals who need to process material quickly while leaving clean edges, it could be tweaked a bit. The higher the blade is set, the more aggressively it can cut because even though fewer teeth are in the material simultaneously, they’re meeting the work at a higher hook angle. So, blade height is a trade-off between speed and smoothness. The higher the blade, the higher the chance of a micro-wobble, especially with less expensive blades. The ideal height is somewhere between the blade’s maximum cut and the slightly revealed gullets.
Of course, the more blade that’s exposed, the more the shop needs to think about safety. Guards and electronic sensors can only go so far. If the material isn’t behaving well (as in, say, reaction hardwoods that want to warp), or the fence isn’t perfectly parallel to the blade, a higher blade can exaggerate the problem and offer a bigger chance of kickback.
The number of teeth on a sawblade is critical. The more teeth, the smoother the cut. But fewer teeth means a faster and cooler cut. On long rip cuts, large and well-spaced teeth can keep up with the feed rate and still deliver acceptable results. For crosscuts on a miter saw, it’s basically the more teeth the merrier. The miter saw’s combination of side grain cuts (across the board) and slow traverse plays to the strengths of small and more numerous teeth, and the net result is a much cleaner cut than a long-grain rip. For clean edges on rips, you’ll need the highest quality saw plate with no flex, and a slightly slower rate of feed – not so slow it heats and burns but not so fast it bogs. The species makes a huge difference, too. It takes some skill, for example, to rip a cord of cherry without burn marks.
There are two common grades of saw plate, stamped and laser cut. Stamped plates are more traditional and less expensive to produce. Most commercial plates are now laser cut and they usually have some geometrical relief cuts, expansion slots and welded in fillers that are designed to dampen sound and to prevent warping from heat build-up. You can usually tell whether the manufacturer has achieved those goals by tapping the face of the blade with a screwdriver. If it sounds dull, odds are it’s a pretty good blade. If it dings like a bell and has excessive resonance, you’ll probably need stabilizers to get good cuts.
The gullet size and frequency in a plate govern the amount of waste that needs to be cleared away during a cut. Larger gullets are found on blades that handle material faster, and those are usually rip blades. The frequency of the gullets is related to the number of teeth, which for wood blades is normally between 24 and 80 on a standard 10” blade. Larger blades on bigger saws have more teeth, so they can cut smoother and of course deeper.
If the plate is well made, the tips are probably made from a decent quality of carbide. The best guide to the quality of the carbide tips on a blade is not some number or rating, but rather the name of the manufacturer. That’s because the carbide industry is not truly standardized, and numbers are not always trustworthy. So, look for a reputable and trusted manufacturer’s name.
One challenge with choosing the right saw blade is that panel goods usually involve more than one material. What might work best to cut through an MDF or particleboard core may be too aggressive to deliver crisp edges in a laminate, melamine or veneer surface. Unfortunately, speed must give way to precision here. Teeth can be ground to meet several tried and tested geometries. There’s the flat top grind (FTG) for ripping; the triple chip grind (TCG) that reduces chipping in brittle laminations while still offering good speed; the alternate top bevel (ATB) that produces a very sharp and precise cut; the high angle alternate top bevel (Hi-ATB) that’s used when a shop needs to make very clean cuts in plywood, laminate, melamine and veneers; and then there’s the combination of the alternate top bevel with a raker (ATBR), which delivers a planing and cutting compromise for great edges.
There are also many standard combination/all-purpose blades that hobbyists prefer because you don’t have to switch them out for different cuts, and that pros like when they plan on further processing such as planing or edge sanding. Some shops also like to use a glue-line rip blade, which has a triple chip grind that delivers an edge so nice that you can pretty much go to glue-up without stopping at the jointer.
A hook or rake is the angle at which the face of a tooth meets the work. Draw an imaginary pencil line from the center of the blade to the front face of the carbide tip on a tooth. If the top of the face (the tip of the tooth) leans forward past this line, it’s an aggressive hook. If it leans backward, it’s a more accommodating rake. Some manufacturers refer to the rake as a negative hook. Most woodworking rip blades will have a 5- to 15-degree hook so that they pull the work into the blade. The softer the material, the bigger the hook that can be used. Sliding miter saws are often set up with a negative hook because the blade is above the work and the tips might grip it if the hook is too aggressive.
Some saw teeth have a relief angle where they’re beveled – they’re thin at the bottom and wide at the top. This helps reduce the tendency to bind, especially in hardwood.
Coatings and other factors
Most manufacturers offer coating options on their blades and other tooling. These are designed to let the blade run cooler, or to stop rust and corrosion, or perhaps to make it easier to remove resin build-up. An old woodworker once said that these coatings are a lot like religion: you must accept them on faith because it’s hard to evaluate them using empirical norms. But one thing that you can evaluate mathematically is the relationship between the RPMs of the saw and the maximum RPMs recommended by the blade manufacturer. If you have an older saw that runs faster, choose blades that are comfortable moving at that speed. Exceeding the recommendations can cause heat buildup, and it can even be dangerous.
It’s surprising how feed rate can affect quality. There’s a sweet spot where most saw blades deliver burn-free, clean edges. Push a little faster or slower and the cut quality degenerates quickly. Over time, woodworkers acquire an innate sense about that rate in different materials and species.
One of the biggest surprises for new woodworkers is that pitch build-up doesn’t mean that a blade is dull. Clean it off and performance usually increases. However, if it’s left on the plate or the sides of the teeth it will cause heat to build up, and that will make a blade go dull faster. There are several commercial pitch cleaners on the market, and concentrated laundry detergent works well, too.
This article was originally published in the April 2022 issue.