Near the end of the last century, a Shaker woman was watching two men sawing a log with a pit saw when a wagon passed by. It was at that moment that a thought occurred to her to put saw teeth on a wheel and use the power of the water wheel to saw trees into boards. The power saw was born! Initially, most of the circular saw blades had teeth resembling those of a pit saw formed into a circular plate of steel. Then, with the advent of the Industrial Revolution, numerous different blade configurations began to appear from many different manufacturers, but they all had one thing in common...they needed to be sharpened frequently.

Then, carbide appeared on the scene...a revolutionary new material that was expensive, but lasted ten times longer than steel. Today, dozens of different-looking blades can be found on the shelves of hardware stores and home centers. It's no wonder woodworking tradesmen and hobbyists alike are often dumbfounded and confused. "Which blade should I use for what job? How do I make the right choice ?" Let's talk about that.

To begin with, it's important to remember that the blade and the table saw work hand-in-hand. A high quality $50 to $100 saw blade will do little to make your "cheapie" $200 table saw perform more admirably. However, put that same high quality blade on your Shopsmith MARK V and the story will be different.

For the sake of clarity, there are two primary terms that will help you understand why saw blades are so varied. Those terms are kerf and set. Since the sole purpose of a blade is to make a cut, it must remove the wood in its path to do so. The kerf is the path cut by the blade as it moves through the wood. If this kerf left by the blade isn't slightly wider than the blade body, binding will result, and that spells trouble in the form of dangerous kick-backs. There must be clearance here...and that clearance is determined by the set of the blade's teeth...the direction or angle the teeth are positioned in order to clear the wood out of their path as they make the cut.

THE FOUR BASIC TYPES OF SAW BLADES

Flat Ground Blades (A) have teeth that are set to alternate at equal right/left angles. These blades actually shave off the wood fibers, much like the knives of a jointer, thickness planer or hand plane.

Hollow Ground Blades (B) are tapered and get narrower as you move from the teeth on their outer perimeter towards the arbor hole near the center. Often referred to as planer blades (because they make such smooth cuts), the teeth of a hollow ground blade have no set and the necessary clearance is provided by the recessed sides of the blade. These blades should be reserved for finish cuts only and should not be used for heavy, sizing cuts.

Thin Rim Blades (C) offer the same basic characteristics as Hollow Ground Blades...except their concave taper is usually only a couple of inches deep, limiting their depth of cut. Thin Rim Blades are always carbide-tipped and are designed primarily for making finish-quality cuts on laminates and tough woods, while taking a narrower kerf.

Swedge Blades (D) feature teeth that are wider than the body of the blade and slightly squared like small spades. The swedge design is common with the chipper teeth on steel stacked dado blades and provides a relatively smooth kerf as it cuts.

It's important to note that no single blade can perform all cuts perfectly. For example, an all-purpose combination blade is designed for both crosscuts and ripping but isn't the best blade for making either cut.

SAW BLADE CLASSIFICATIONS

Saw blades are classified as rip, crosscut, or combination (also referred to as all-purpose) according to their assigned task. They're made of either high carbon steel, alloyed with nickel and chrome -- or of tungsten carbide-tipped steel.

Rip Blades (1) have large, chisel-shaped teeth and have been designed to cut only with the grain of hard or soft woods (cutting to width). They should not be used for making cuts across the grain of the wood. They feature deep gullets between the teeth for removing large shavings as they create a clear path for the following tooth. While steel rip blades offer flat or bevel ground teeth that are alternately set, their carbide-toothed counterparts offer square top ground (or flat ground) teeth with no alternate set.

Crosscut Blades (2) are designed to cut only straight or diagonally across the grain of hard or soft woods (cutting to length). They should not be used for making rip cuts with the grain of the wood. Crosscut blades work equally well on solid woods, plywoods, particleboards or veneers. The steel version of these blades feature small, alternately set teeth, beveled front and back to a sharp point, while their carbide-tipped counterparts also have similarly ground teeth as well as a triple chip grind.

Combination Blades (3) are good general purpose blades for both ripping and crosscutting. They're the number one blade of choice for most woodworkers because of their versatility...but remember, they're not the best blade for either job...just the most economical alternative. Carbide-tipped combination blades do an admirable job of cutting thick or thin hard or soft woods, plywood or particleboard.

Plywood Blades (4) are made specifically for sawing plywood, paneling and veneers. They offer fine, tiny teeth to eliminate splintering and fraying of single and multiple layers of thin wood. They work equally well for ripping, crosscutting and mitering stock up to 1" thick.

CARBIDE-TIPPED BLADES

There are two primary factors to consider when deciding whether to purchase steel or carbide-tipped blades. Those two factors are cost and durability. Although carbide-tipped blades last up to 10 times longer before re-sharpening is necessary, you will typically pay two to three times as much for them as for their steel counterparts. If you use your table saw for more than an occasional cut...or if you're often cutting tough hardwoods or man-made materials such as particleboard, MDF (medium density fiberboard) or laminates...you'll be better off in the long run with carbide-tipped blades.

The durability of a carbide-tipped blade comes from tungsten carbide, a powder, electronically derived from steel that's mixed with a binder material and fused under intense pressure at an extremely high temperature. The resultant incredibly hard material - Cemented Carbide - is then brazed to the steel blade.

Carbide blades (5,6,7) are classified on the basis of two factors -- the grade of the carbide used in their construction -- and the grind of their teeth. Carbide is available in four grades of hardness: C1, C2, C3 and C4. The softest (C1) offers the highest resistance to shock (such as hitting a hidden nail in the wood), and the lowest resistance to wear (requiring more frequent sharpening). On the other hand, C4 carbide is the hardest and most brittle. That means it offers the lowest resistance to shock and the highest resistance to wear. You'll sharpen a C4 blade a lot less but hitting a hidden nail will most surely chip the teeth or break them off. C2 carbide is the most common grade for rip blades, while C3 or C4 are more common with crosscut and combination blades.

Carbide Blade Teeth are wider than the body of the blade and typically have no set. Where the teeth on steel blades are ground on the fronts, carbide teeth are ground on their tops as well as their fronts and sides. The three most common grinds for carbide teeth are: 1 - Square Top Ground (5) for ripping wood with the grain ; 2 - Alternate Top Bevel Ground (7) for cutting with less resistance and leaving a smoother finish. Their teeth are ground to alternating left/right bevels to shear the wood fibers during the cut and sawing man-made materials ... where the smoothness of the cut is important; and 3 - Triple Chip Ground (6) for cutting man-made materials with minimal surface tear-out. Triple Chip Ground Blades feature a combination of alternate top bevel and square top ground teeth with the corners ground off. As a result, they deliver a better quality cut than an alternate top bevel ground blade.

TIPS FOR SAW BLADE SAFETY & MAINTENANCE

It's important to remember that table saw operations lead the list of in-shop accidents. But, like ALL power tool accidents, they're preventable by simply using common sense and avoiding the use of hazardous techniques. First, be sure your table saw and accessories are properly and accurately aligned. Also, be aware that a dull blade (or one that's covered in pitch) is NOT safe to use. If the blade binds, the stock can kick back toward you, resulting in personal injury. NOTE: The glues and resins used in man-made materials such as particleboard and MDF...and the resins used in laminates WILL cause rapid dulling of your blades (more so, of course, with steel blades than with carbide-tipped blades)...and that can spell DANGER. So, keep your blades sharp. Don't force tough stocks rapidly through a cut, as this can result in overheating and warpage. And keep your blades free of pitch and gum by using a saw blade cleaner frequently.