Glossary of saw tooth styles
Dictionary of carbide teeth with close-up pictures of tip shapes and details. Identify carbide tooth styles and find information on angles, names of parts and definitions.
ATB: Alternate Top Bevel
Tips with one corner pointed on top to shear across fibers are called Alternate Top Bevel style. This means half cut on one side, the rest on the other. A tungsten carbide tooth usually has a flat face with edges on both sides. In a variation of ATB, each tip has an alternate bevel on the face, so only one side has an acute edge. This type is relatively rare. How neatly ATB tips cut depends on variable factors such as spacing, whether there's a positive or negative hook angle, and the degree it is slanted. It ordinarily slants 10 or 20 degrees; not as high as the HATB kind.
Acutely pointed High Alternate Top Bevel tips are beveled 25 to 40 degrees for shearing and slicing. They have a negative hook angle. These modifications can neaten the passage through extraordinarily fragile stock. Save Hi-ATB for delicate finishing details. HATB deflects more than a TCG shape. All the different styles of teeth with extremely pointy shapes share a vulnerability. Alternate bevel teeth dull faster than triple chip shapes.
Most shapes, as in the pictures above, have each tip narrowing vertically from top to bottom for side radial clearance. Ample tapering scribes characteristic curved lines. This typical taper is the opposite of a cone, which would be narrow at the top. A conical shape is is quite unusual and is used just for superficial scoring.
For side clearance, carbide teeth are not normally set or pried outward. Instead, they are shaped for clearance in both the vertical and horizontal planes. In this close-up picture looking at tangential clearance from above, tips extend outward on both sides in the horizontal dimension. This is necessary so that the sides won't rub. The profiles protrude slightly at the face and taper in toward the back. If the difference is subtle and the tapering is barely noticeable, the cut surface of your material will be polished. That effect can occasionally be desirable, in exchange for lost efficiency. Ordinarily though, you want plenty of elbow room to spare for efficient operation.
The shoulder is the part behind a tip supporting it. For back clearance, the shoulder profile descends slightly.
The rim has a low opening before each tooth. If the open parts are big and rounded, they scoop out sawdust efficiently and help cut fast. Little gullets fill up and retain heat.
A concave curved hollow ground face has acute side edges. Those parts of the tip are meant to pierce easily, at least until their razor edges round over. Curved tops are found on a few rare styles. These unusual kinds of tips are vulnerable and costly to maintain. A practical alternative is HATB.
Hook angle, negative or positive
The way a saw tooth leans is called hook or rake angle. A radius is a line from the center to the rim. You can define a face cutting angle by its degree off the radius. Thus, zero rake is simply straight up.
Positive hook angle leans forward to move stock rapidly. This common detail is desirable when you rip, but not on overhead models where positive rake would pull too much.
Negative hook angle leans back, as in the right picture. The scraping of negative hook creates some resistance, which inhibits pulling. The reason why you might want cutting angles that are leaning back is that they are beneficial when you need to push at a gentle, controlled pace in order to gain a neater result.
Rip style teeth
The obvious feature of a rip profile is its big deep gullet. The purpose of it is to rake out dust and get things moving along quickly. To go with the grain, the style of a rip table saw blade has an aggressive +20 degree positive hook and plenty of side clearance. Usually a rip profile is flat on top as shown here. (Triple chip is seen on some varieties.)
Because a raker tooth serves a similar purpose, it also has the flat shape or F style. A raker opens up combination patterns which are primarily alternate top bevel. It is inserted between and slightly below the level of the groups of other tips. It typically has the capacious gullet, but sometimes has a bit less hook.
TCG: Triple Chip Grind
You can identify a carbide tooth style called TCG by its pattern of a high, chamfered, cornerless tip alternating with a low flat topped one. It occasionally goes by the name TC and F. In the picture, the face view detail shows only the corners of the flat one behind. Triple Chip Grind can stand up to dense, tough composites. Because the shape is beveled on both corners and balanced on center, TCG is a stable design that makes a very neat cut. Triple chip style has versatility to excel in a variety of manmade materials, and it rips well. For slicing across natural wood grain fibers, triple chip teeth cut somewhat rougher than alternate bevel tips.
California Triple Chip Grind is a variant of the TCG pattern. It represents somewhat of a multipurpose compromise in the middle between other styles which are more dedicated to their specific purposes. The flat tops of C-TCG have just one corner removed on alternate tips. CTCG is not so common as the triple chip style.
On each tooth, a square chunk called a Tungsten Carbide Tip is inserted. The carbide grade in the tip itself may be varied to suit an application. The parts are first individually secured and then they are shaped.
Since both sides of carbide tips cut, fewer carbide teeth are needed than with steel. Count the full number per dia. You might find a number marked such as 60T, or Z60 for zahn in German.
The tip count on a 10 in. dia. ranges from 12 to 100T. The average is around 40 or 50T. Tooth spacing makes a significant difference in rate. Closely crowded ones feed cautiously and cut hard stock cleanly. A low count, coarsely spaced by big gullets moves without hesitation, but may cut less neatly.
With each increase in circular saw blade dia., approximately 20T are added to keep the same effect. These tooth counts are roughly comparable:
- 7 1/4 in. 40T
- 10 in. 60T
- 12 in. 80T