Blade Types

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Blade Types By David Fielhaber
There are so many blade types out there, that buying a new blade for your table saw, band saw or scroll saw can be confusing. The main problem seems to be too many terms and not enough definitions. Another problem is blade types, which seem to provide similar results on the same material or materials, which need different blades depending on the cut. I'll start with circular saw blades, then band saw and finally scroll saw blades.
Circular Saw Blades Alternating Bevel - ATB. This tooth design is the most familiar with the teeth alternating between leaning to the left and right. The top bevel can range from 10 to 20 degrees. It is best for providing a slicing action in cutting across the grain in solid wood, for melamine and general-purpose cutting but does not rip very well.
Triple Chip - TCG. The triple chip is named for the shape of every second tooth. This tooth is slightly higher than the Flat tooth it precedes, plus it has had the corners removed. Because of this, the tooth makes a narrow groove just before the final cut and helps to eliminate chipping in hard or brittle materials like melamine and laminate. Excellent finish cuts in solid wood and laminated veneer.
Hollow Ground - HG. Hollow ground teeth as the name implies have a cupped shape to them. This means the outer edge has a slicing action just before the middle part of the tooth makes the final cut. This is a different solution to the same problem that TCG blades were made for. Designed for clean chip free cutting in melamine. Sharpening these blades can be difficult, and someone who is not familiar with them can ruin the hollow grind, turning them into a flat tooth.
Flat or Chisel - This tooth design, with its flat-topped shovel like tooth was originally only for ripping. Now you can find them recommended for cross cutting and general purpose as well. I don't recommend them for cross cuts in solid wood because they provide no slicing of the grain. Only when brand new can you get a clean cross cut but as they dull they will tear the grain. Designed for cutting with the grain in ripping cuts. Also can be used for plywood.
Combination - Designed to do it all. They normally have a series of ATB teeth for crosscuts, followed by a flat-topped raker tooth for ripping. You will not get sand free cross cuts, but it does mean you do not have to continually change blades. It does everything good but nothing great.
Hook or Rake - This is the angle of attack that the tooth hits the material. If you place a straight edge though the center of a blade up to a tooth you will see this angle. Angles range from 20 degrees to negative 7 degrees. Solid wood is best cut with teeth with a positive hook, while melamine, laminates, aluminum and plastic should be cut with a negative hook. Also, sliding compound saws should be equipped with a negative tooth blade because of the action of the saw is different than a table saw.
Kerf - The kerf of a blade is the width of the tooth and therefore the width of the cut you will be making in the material. When you use a thin kerf blade your saw does not have to work quite as hard and in expensive material you are not wasting as much. Both of these benefits may be negligible but can mean more for smaller saws in the long run. A draw back is that you have a blade, which is thinner and therefore not as rigid. A final thing to keep in mind is when you change blades with different kerfs, you need to zero out your fence each time.
Anti-Kickback Shoulder - This raised shoulder limits the amount of material a tooth can bite into as the blade passes through. This means you have to reduce the feed rate slightly but the reward is a much safer blade. If a tooth bites too much material it can either lift it away from the table surface or in the case of a radial arm saw the blade might ride on top of the material. Both of these situations are dangerous. On the table saw the lifted material can be shot backwards at the operator causing a serious injury. On a radial arm saw, if the blade rides on top of the material the blade & housing can run straight out on its tracks and remove fingers just as easy as cutting spruce. Blades with over a certain number of teeth do not have room for shoulders, but the tight packing of teeth actually help in limiting the bite.
Expansion Slots & Copper Buttons - Expansion slots are usually laser cut lines, loops, spirals, etc. cut into the body of the blade which help prevent the blade from distorting by centrifugal force and as it heats up. This means a blade, which stays flat and true before, during and after use. Copper buttons also act to help dissipate heat by absorbing it faster and away from the blade body.
Gullet - The gullet is the small hollow in front of each tooth. The chips and dust are caught in this space and ejected, preventing build up and clogging.
Plate or Body - This is the steel disc making up the flat surface of the blade and the carbide teeth are attached to it.
Clearance - This is the distance from the outside edge of the tooth to the outside edge of the body. The smaller the clearance the more chance of burning is the material is twisted or skewed while cutting.
Top Bevel - This is the bevel angle on an ATB tooth. The greater the angle the more of a slicing action the tooth will make as it cuts the material. This is especially important in making cuts across the grain.
Relief Angle - The relief angle is the back bevel from the top of the tooth backward away from the cutting edge. All teeth have this regardless of design. If they didn't the back of the tooth would actually strike the material first and batter it instead of cut it.
Tensioning Ring - Most blades have a slight ring about 2/3's or ž's away from the arbor hole. This shows that the blade has been pretensioned to stay as flat as possible while being used.
Band Saw Blades Regular - Fine equally spaced teeth with 0 degree face angle. This tooth gives you smoother cuts. Skip - 0 degree face angle. Fast cutting & chip removal because of the extra large gullet. Excellent for thicker woods, plastics and composition material. Hook - Positive face angle. Fast cutting rate but rough surface and is good for longer cuts. Best for thicker wood, plywood and composition material. Bimetal - Longer lasting, finer teeth suitable for metal. Some bi-metal blades now being made for wood cutting.

Choosing correct number of teeth per inch. Fewer teeth - faster rougher cut. More teeth - slower smoother. General rule of thumb - at least 3 teeth in work piece. 32 - 18 metal, plastic, wood under ź" 14 - 4 general wood cutting 3 - 2 cutting thick stock and resawing
Scroll Saw Blades
Regular Tooth - Good general purpose blade. Cuts everything including non-ferrous metal, but leaves tear out on the bottom surface of wood. Must cut slowly to reduce chance of burning because chip clearance is not as good.
Skip Tooth - Best for soft woods but still good for hard woods and plastic. Fast cutting and good chip clearance. Provides a fairly smooth finish.
Double Tooth - Best for softwoods and plastics. Provides very efficient chip removal. They are fast cutting and give clean edges but not smooth.
Precision Ground - Best for Hardwoods. Provides smooth and accurate cuts on most material and lasts longer then other blades. Minimizes burning and has rapid chip removal. Can be in skip or double tooth and are normally reverse tooth to reduce tear out.
Crown Tooth - Replaces regular tooth as best general purpose, except metal. Smooth, almost sand free finish. Design cuts on both down and up stroke reducing splinters. With no top or bottom, the blade lasts longer since you can turn it up side down and use the upper portion.
Reverse Tooth - Normally associated with skip or double tooth patterns. Provides splinter free cutting in wood & plywood by cutting on the up as well as down stroke.
Spiral - Blades have the teeth cut and then are twisted into a spiral so the cut in any direction without turning your material. Draw back is a rougher cut and wider kerf.
Metal - Hardened and tempered steel to cut ferrous and nonferrous metal. Regular tooth pattern.
Pinned - These blades are wider and thicker in order to have a small pin in the ends. They normally come in regular or skip tooth patterns but are tougher to find. Most new scroll saws are not set up for pinned blades. Draw back is poor selection and because they are wider they cannot cut tight radius, but because of this they can cut straight better without as much fluctuation.