The cutting tools that get the heaviest use in most woodworking shops are those that use circular saw blades. These tools include the table saw, radial-arm saw, power miter saw, and handheld circular saw, and blades designed for each of these tools share most of the same characteristics—often, a particular blade can be used on several tools. As your woodworking skills and experience expand, it's likely you will find it useful to own three to five different blades, each designated to a particular type of cutting. Choosing blades for any of these tools requires a consideration of several options.
The first choice you have is the size of the blade. Circular blades are identified by their diameter, and each saw specifies the largest blade that will fit the tool. Handheld circular saws typically use 7 1/4-inch or 8 1/4-inch blades, but there are also specialty panel saws that take a maximum size of as little as 4 1/2 inches, and contractor-grade worm-drive circular saw that accept blades as large as 9 inches.
For stationary saws (table saws, radial-arm saws, miter saws) the most common blade size is 10 inches, though 12-inch saws are also available. There are also 8-models, but these are usually very lightweight saws that aren't very suitable for major woodworking projects, though they can be fine for hobbyists who limit their work to smallish craft projects.
While it is not generally recommended, you can mount a smaller blade in a saw specified for a larger blade size. But under no circumstances should you mount a larger blade than the saw's specified maximum size.
Material to Be Cut
Many blades are marketed as suitable for cutting many different materials, but manufacturers also offer blades designed for specific types of building materials. For example, blades may be specified for plywood, melamine, or laminate. This designation mostly assures that the tooth count and tooth size is appropriate for the material. This is not to say that a good-quality combination or general-purpose blade cannot be used to cut these materials, but if you cut them frequently, you may want to invest in blades specified for these materials.
Basic Blade Types
Next—and arguably the most important distinction when choosing a blade for a circular-action saw—is the basic type. There are four general categories of blades used on circular-action saws:
- Crosscut blades have teeth that integrate sharp chisels welded to the tips of the teeth, often made from carbide steel (these blades are often marketed with the phrase "carbide-tipped). On these blades, the teeth and cutting chisels are slightly angled ("set") so the alternating teeth point in opposite directions. This creates a slightly wider cutting slot (kerf) that makes the cutting action more efficient and cleaner. This can produce a very fine finish on most materials. Because it is harder to cut wood fibers cleanly when cutting across them, these blades tend to have smaller, more plentiful teeth. Crosscut blades are used on table saws and radial arm saws, and are the only type used on miter saws.
- Rip-cut blades are designed to cut parallel to the grain of the wood. A rip-cut blade has fewer teeth than a cross-cut blade, but they are longer with deeper gullets between them. This helps to help clear away the material as it is cut. Rip-cut blades can cut quite quickly. They are often used for ripping duties on table saws and radial arm saws, but are never used on miter saws, which perform only cross-cutting duties.
- Combination blades are engineered with a shape that offers the benefits of both rip-cut and cross-cut blades. They are designed so that a rip tooth alternates after every few crosscut teeth. These blades are a good choice for casual woodworkers who don't want to change blades frequently between cross-cutting and rip-cutting tasks. They are used on table saws and radial arm saws.
- General-purpose blades are sometimes confused with combination blades, since they serve the same purpose—to crosscut and rip cut with equal effectiveness—but the design is different than that of a combination blade. Here, the teeth are all the same size and shape—slightly larger than those found on a combination blade, with a more pronounced bevel on the cutting edges. These blades have begun to replace traditional combination blades for many woodworkers.
While the basic crosscut, rip-cut, combination, or general-purpose blades will serve the majority of cutting duties in a woodworking shop, there are also specialty blades that many skilled woodworkers find helpful:
- Panel blades have a large number of relatively small teeth with a less aggressive hook angle. They are designed to produce smooth cuts in panel sheet goods, such as laminates, plywood, and solid-surface material. These are normally used with materials that may chip or break when cut with regular circular blades. These blades are sometimes specified for a particular material and can be labeled a number of different ways: "laminate and plywood," "industrial glue" (designed for cutting through the glues used in plywood), or "solid-surface" (for cutting materials such as Corian®).
- Diamond-tipped are used for cutting masonry, and are used more often with portable circular saws rather than stationary table saws.
- Hardened blades are used for cutting thin sheet metals, such as steel, copper, or aluminum. Some varieties are labeled "non-ferrous metals."
- Dado sets are specifically used for woodworking projects that call for cutting grooves for various dado joints, using a table saw or a radial-arm saw. The two types of dado blades are: wobble blades, where the blade is adjusted to a particular angle to create a dado; and stacked dado sets. Wobble dado blades can create a considerable amount of vibration, which can be a bit unnerving when in use. Additionally, wobble blades don't leave the cleanest dadoes for your joinery. A stacked dado set consists of a full crosscut blade on each side of the arbor, with smaller "chippers" in the middle. The chippers are typically either 1/8-inch or 1/16-inch in thickness. The width of the dado is dependent on the number of chippers on the arbor between the two blades. A typical stacked dado set will be able to cut dadoes between 1/4 inch (using no chippers) to 13/16inch (using the entire complement of chippers).
Circular saw blades are generally categorized by the total number of teeth they include, rather than by teeth-per-inch (TPI), which is the standard for bandsaw and jigsaw blades. There are general rules of thumb when it comes to the number of teeth on circular blade: Rip-cut blades generally have the fewest teeth, panel blades have the most, while crosscut blades, combination blades, and general-purpose blades fall between the extremes. A 10-inch combination blade for a table saw, for example, can range from as few as 24 teeth to as many as 80 teeth; an average woodworker finds that a 40-tooth combination blade gives good results for most cutting. With 12-inch blades, you can find blades with as many as 96 teeth.
The rule to remember is that the more teeth, the finer the finish. Blades with a low tooth count will cut very aggressively but leave a relatively rough finish, whereas a greater number of teeth will leave a cleaner finish but will cut slower.
Thin-Kerf vs. Full-Kerf
Specialty blade manufactures may offer essentially same blade in both thin-kerf and full-kerf versions. Full-kerf blades leave a cutting slot about 1/8 inch in width, while thin-kerf blades leave a kerf of about 3/32 inch. Your choice of which blade to use depends mostly on the power of your saw's motor. Full-kerf blades require more power to drive, and are best suited for saws with motors at least 3 hp. Thin-kerf blades are less likely to bog down, and work well with saws that generate less the 3 hp.
While circular blades can all look the same, there is a substantial difference between how cheap blades and premium blades are engineered:
- Usually made of standard stainless steel
- Carbide tips, if present, are relatively small, and can't be resharpened
- No Teflon coating to lessen friction
- Blade body made of high-speed carbide steel
- Blade coated with Teflon or another lubricant to reduce friction
- Cutting tips are made of carbide, and are oversized to allow for repeated sharpening.
- May have slots cut into blade to reduce expansion due to friction heat
Good cutting performance requires more than just selecting the proper blade size and style. Before each work session, you should also inspect the condition of the blade, which may require test cutting on scrap material. When you've used a saw blade for a period of time, they can become dull or caked with pitch and thus less effective. Dirty blades can also be more susceptible to dangerous kickbacks since wood stock will not pass through the saw cleanly. If a considerable amount of pitch has collected on the carbide tips, there are cleaning solutions available at your fine woodworking supplier to remove the pitch.
It's equally important that your blades be sharp, as sharp saw blades are much safer to use. If you purchase quality carbide blades, they can be sharpened by a professional saw sharpener, which will increase the life of the blade. Some companies that make high-quality saw blades, such as Forrest, offer sharpening services through the manufacturer's website (for a fee, of course). However, quality blades can be sharpened a number of times, which will help justify the increased initial cost. Better quality blades kept sharp will cut quicker and cleaner, and keep their edge longer.