The capacity of any type of saw (not just circular saws) is the maximum material thickness which it can cut. Larger capacity means the saw is able to cut thicker sheets. For all types of circular saws, this is normally considered to be 1/3 of the blade’s diameter in most materials. The usual diameters are 6-1/2″, 7-1/4″, 8″, 10″ and 12″. According to this, typical woodcutting blade with 12″ diameter has 4″ cutting depth. There are times when it is possible to cut up to 45% of the blade’s diameter, but that usually requires removing safety guards, which is not a good practice. This is typical of large circular blades.
The Deepest Cut
Capacity is one of the major factors which power tool manufacturers take into account when designing a saw. Everyone wants the biggest capacity possible, so that they can cut the thickest material possible. Working with a saw blade with greater capacity enables you to make cuts in one go. Therefore, saw designs, especially the designs of safety guards, are done with the idea of making the deepest possible cut. The other exception which limits the capacity of a saw is the material being cut. Cutting depth for masonry and concrete is larger than the one for tile or stone. Plastics and Plexiglas in particular limit the saw’s capacity to only about 15% of the blade’s diameter length. This isn’t so much because of the saw, but the ability of the material to dissipate heat. When plastics become too hot, they can melt. So, deep cuts can cause you to melt through the material, rather than cut through it. Plexiglas tends to crack when it expands rapidly from heat. If cutting lumber, remember that the blade won’t have the same capacity when rip cutting and when crosscutting.
Motor and Saw Blade Size
Motor size is also a consideration for saw capacity. Small capacity saw blades are lightweight and easy to manage. But if you look at a selection of circular saws, you will see that the larger the saw blade, the more powerful a motor is installed in the saw. That’s because the larger blade will have a greater amount of surface area in contact with the material being cut, increasing the friction. Cutting through a 4 x 4 post requires considerably more power than cutting through a 3 x 4 stud.
When making a cut only partially through a thick piece of material, it is always useful to use a blade depth gauge for depth adjustment. These stepped gauges, typically made of aluminum, allow you to precisely determine the distance from the table to the teeth of the blade, on either table saws or radial arm saws. Always verify your adjustment by making a test cut on a piece of scrap after adjusting. With the help of these tools, the precision of cut is outstanding.