Nature spent years growing the wood we use, and then we spend a few minutes cutting the wood into small bits and pieces. And the truth be told, we really do not cut wood. Rather, we tear it apart with a saw blade that we force through the wood. So, let's look more closely at the circular saw blade.
The first step to understanding circular saw blades is to learn the vocabulary.
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.
Collars. The washers that are on each side of the blade when the blade is attached to the arbor are called the collars. The collars not only hold the blade to the arbor, but they also stop wobble and effectively increase the blade stiffness. The collars 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 inch 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 mean 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. 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.
Tooth point. Same as "tip of the tooth."
Now you have a grounding in the basic language of circular saw blades. Next month we'll talk about some of the factors that are important to consider when choosing and using these blades.
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