Question
In my shop I have a Unisaw that is my primary tablesaw for the shop. I use one blade when I cut veneer and MDF and I have a separate blade when I cut hardwoods. Does anyone leave one blade in the saw for all cuts or is it best to change blades? What kind of blades do you like the best?
Forum Responses
(Cabinetmaking Forum)
From contributor Z:
I use a few different blades. I use one for rough sizing of hardwoods, one for plywood, and one for final dimensioning of hardwoods. Forrest woodworker II has been my favorite overall.
First, a bit of terminology.
Body or plate: the body or plate is the main piece of metal used to make the saw blade. The teeth are fastened to the outer rim. The center has a hole to accommodate the arbor.
Collar: the washers that are each side of the blade when the blade is attached to the arbor are called the collars. The collar not only holds the blade to the arbor, but also stops wobble and effectively increases the blade stiffness. The collar should be as large as practical for best stability, especially with thinner blades. (Many collars are too small, in my opinion.) The collar must touch at its outer perimeter, so often one of the collars is hollow ground while the other is perfectly flat.
Gauge: the measure of the plate thickness. A typical saw, for example, could be 0.125" in thickness.
Gullet: the space between the teeth and the body of the saw. This space holds the sawdust while the teeth are in the cut. The gullet must be large enough to hold all the sawdust produced. A full gullet means that no further cutting can be done; slower than normal feed speeds will have to be used, plus the blade may vibrate excessively. Larger gullets are required when making deep cuts (that is, when sawing thick pieces). Slow feed speeds when gullets are too small means fine sawdust, low production, heating and short saw life (rapid dulling). Gullets should be rounded without sharp corners to avoid cracks and breaks.
Kerf: the width of the slot in the wood that the blade makes when sawing, is the kerf. For practical purposes, the kerf is the same as the overall width of the saw teeth, called the set. Technically, after the teeth cut the wood, the wood actually closes the slot or springs-back a very small amount giving a narrower kerf.
Number of teeth: circular saws are specified based on their diameter and the total number of teeth the have. Closely spaced teeth make fine, smoother cuts, with less chipping and slivers (preferred for plywood and sheet materials) while wide spacing makes coarser, rougher cuts. Closely spaced teeth tend to make more fine sawdust and potentially heat more, causing the blade to wander a bit at times.
Set: in order to create enough room for the body of the saw to pass through the wood without rubbing, the saw teeth are made a bit wider than the body of the saw. The extra width on each side of the body of the saw is called the side clearance. The set is the total width of the teeth. Avoid large sets as they will greatly affect yield and profits.
Side Clearance: see set.
Side of the tooth: although the top of the tooth does a lot of cutting, when ripping a piece of wood, it is the sides of the teeth that prepare the ripped surface. Hence, the sides must also be sharpened.
Side Dressing: it is oftentimes important that the sides of the teeth be sharp and also be perfectly aligned so that they produce a smooth surface. This process of sharpening and aligning is called side dressing.
Teeth: the teeth are the part of the blade that cuts the wood. The teeth cut a slot, called the kerf, in the wood that is a little bit wider than the thickness of the plate, so the plate can move through the wood without rubbing.
Top of the tooth: the part of the tooth that does the actual cutting or scraping of the wood is the tip or top of the tooth. Some manufacturers of inexpensive band blades do not have extremely sharp teeth when the new blade is shipped - this is bad news.
Tooth point: same as tip of the tooth.
Saw Plate Thickness: the plate of a saw blade is often 1/8 to 1/4" thick. The thinner plate means that there is less sawdust and so potentially less waste. However, thin blades, often called thin-kerf blades, are very sensitive to heating and wobbling, which in turn means non-straight (wavy or snaky) cuts. As a result of this one factor, most people opt for a thicker and therefore stiffer plate. When someone comes up with a thin-kerf, stiff plate, it will sell like hot cakes and improve wood manufacturing profits.
Saw Tooth Design: there are four basic tooth designs for circular saws:
Flat-Top Grind (FTG). These teeth, as the name implies, have a flat top. They are shaped like miniature chisels. They are best suited for ripping as they are fast. It is critical, if the ripped edge will be glued to, that side dressing is perfectly done. It is surprising how often saw shops fail to do a perfect job, so the ripped edge quality is poor.
Alternate-Top Bevel (ATB). These teeth, as the name implies, are beveled on the top, with every other tooth being beveled in the opposite direction to the adjacent teeth. The bevel angle can range from 5 to 40 degrees; 10 to 20 degrees is most common. (FTG is 0 degrees.) With this angle, the tooth cuts with a shearing action and this limits tear-out or chip-out. ATB teeth are usually more closely spaced than FTG. This tooth can be used for ripping and crosscutting.
ATB and Raker (ATB&R). This sawtooth design consists of typically four ATB followed by one raker, which is basically an FTG tooth. With the ATB, the cut is clean, but has a beveled bottom. The raker tooth cleans up the kerf to achieve a flat bottom. This would be important with dado cuts or other cuts that do not go all the way through the workpiece. The 40-tooth ATB blade has replaced this blade in many cases.
Triple-Chip (TC). With the triple chip, the teeth resemble a FTG, but then the outside edges of every other tooth are chamfered at 45 degrees. The tooth that is not chamfered is called a raker tooth. The chamfered tooth makes a rough cut and then the raker cleans up the cut. This blade is especially suited for particle board cutting. It does okay with solid wood, but not as well as an ATB.
Hook: the angle at which the tooth face is at compared to a radius from the center of the plate is called the hook angle. (Rake is the same angle, but usually rake is applied knives.) The larger the hook, the more the blade wants to climb into the wood; a saw with large hook is called an aggressive saw. The large hook also means rougher cuts (that is, more tear-out).
On the other hand, the smaller the hook angle, the more force it takes to push the blade into the wood. In fact, with a radial arm saw, the hook is usually zero degrees so that the saw does not climb into the workpiece and stall or create a safety issue. However, zero hook for crosscutting and ripping can force the workpiece to come flying back out of the saw toward the operator- -slow enough that it can be seen but too fast to move out of the way. For rip saws, the hook is 15 to 20 degrees typically. For crosscutting, 10 to 15 degrees.
Preferred Saws: certainly there is a lot of debate, but the following are my thoughts about the “best” saws: crosscutting solid wood and cutting plywood. ATB with 40 to 80 teeth on a 10" diameter blade and 10 more on a 12" blade, depending on the quality of the cut required
Ripping solid wood: ATB with 40 teeth on a 10" and 50 on a 12"; or FTG with 20 to 30 teeth on a 10" and 10 more on a 12". Cutting composite wood materials - TC with 80 teeth on a 10" blade and 90 or more on a 12"
Radial arm saw: as above but also with zero hook – very important.
Tooth Material: although a few saws use steel teeth, almost every modern saw uses carbide tooth tips that are brazed onto the steel body. Carbide consists of a mixture of tungsten, carbon and cobalt. It last 50 times longer when cutting wood than steel teeth. Carbide is very brittle, so the saw must be handled very carefully once off the arbor. There are other materials used for teeth including diamond and Stellite.
Saw Quality: with saws, the old adage is true: “You get what you pay for.” Expensive saws are flat, have quality brazing of the carbide tips, and have expansion slots for accommodating any heat. For most commercial installations, a good everyday blade should cost no less than $50 and perhaps even $75 or more. Remember that proper side dressing is critical. Once the blade is mounted on the arbor, it should be flat. When turned by hand, it should not have any wobble or run-out. Use a micrometer to check this. Run-out can be a problem with the blade or, more likely, a problem with the arbor bearings or the collar flatness. Avoid heating the blade. One cause of heating can be a dull blade. Heat can ruin the blade quickly. Keep the saw clean. Commercial oven cleaners will dissolve the glue in the carbide, so avoid this product. Paint remover is OK, but the fumes can be dangerous. I prefer commercial blade cleaning products. Certainly the setup of the saw machine itself is also important, but is not covered in this article.
Safety: please be careful with a saw. It does not know the difference between wood and fingers. Use all safety devices. Avoid kickback hazards.
You can use a general purpose blade for most things, but sometimes it's better to use specialized. For instance a rip blade will work faster and last longer than a general purpose blade if you’re ripping a lot of stock. A crosscut blade will give a much cleaner cut than a general purpose. It comes down to how much quantity your doing and does it merit buying and changing blades frequently.
If the carbide and its fastening is designed to be 200% stronger than needed, it is possible that, with a saw not sawing knotty, dry, dense hardwoods, the loss of strength will not affect performance until the loss exceeds 50%. I suspect that an expensive blade has this over-design.
Incidentally, I only have two different types of tablesaw blades in my shop - a glueline rip blade (24t or so) which is used for hardwoods with a feeder, and a 60t crosscut blade which I use for most everything else (clean double sided cuts on all except for melamine, which will chip one side).
I use those blades on my 16" Tannewicz which has a measurable amount of runout. Yet still can achieve better results than my neighbor with their beam saw with scoring blade on sheet goods.
A good sharpening facility will extend the life of the blades for a good deal of time and you will be pleased with their performance when they come back. A poor facility will rob you of money in the blade and the sharpening.
We run a slider and we have Freud triple chips in it with a scoring blade. We run a lot through it from melamine to solid wood, even solid surface occasionally. They are great blades, but they have a lot of carbide. We change out to ripping, solid surface and other dedicated blades when we have a need to cut a lot of a certain material. So for us the triple chip is what stays on most.
