You’re in a bind. You have a 7 ¼” circular saw, but the blade has become warped, or maybe dull. The only other blade you have that is usable is a 7” blade (referring to its diameter) – it’s not warped, and it is still sharp. Is it okay to use, even though it’s smaller? Is it the wrong blade for the saw?
Circular saws are an extension of a carpenter’s arm, ubiquitous on job sites, generally used in the shop as well. It’s a versatile power tool, easy to use, easy to carry on the job, and well suited for many cutting tasks. On job sites, it’s the perfect tool for trimming framing lumber or ripping a 4’ x 8’ piece of plywood panel.
With compact, powerful motors, it’s capable of filling many roles in a single day: scoring concrete, trimming roof decking, and ripping a 2×4 lengthwise, for instance. Lightweight, and with a comfortable handle, it can go up the ladder with you easily for framing and roof jobs, and serve as a substitute for a table saw in the shop.
Generally speaking, the standard size circular saw uses a 7 ¼” blade, and has a cutting depth capacity of about 2 ½”. No matter the size, though, the maximum depth of cutting capacity of a circular saw will be less than half of its diameter. The circular saw blade is secured to the saw and rotates on an arbor at the center of the blade, and you are not able to cut to the arbor.
One of the features that helps the circular saw stand out is that its blades can be used interchangeably among various devices, including miter saws, table saws, radial arm saws, and other circular saw brands. The question becomes whether that interchangeability extends to different diameter blades.
Circular saws do accept smaller blades, and in this instance, a 7” blade can be used on a 7 ¼” circular saw.
Implications of Using a Smaller Blade On Your Circular Saw
While you can use the smaller blade on your circular saw, there are some implications to consider.
- Cutting Depth. As mentioned above, the cutting depth will always be less than half of the blade’s diameter. When you use a smaller blade, the depth of the cut you can achieve will also be less. You’re going to lose some depth with the 7” blade, and if depth is important to your cut, you’ll need to get a new 7 ¼” blade or have the old one sharpened.
The depth will not change significantly, though, since the blade size difference is so slight, and you will probably be okay. If the difference in blade size was greater, too, cutting depth could be an issue.
Cutting depth indicators on your saw might no longer be accurate, too, if the difference in blade size is greater than the one we are discussing. You’ll need to account for that in your measurements, so be aware of this if you use a significantly smaller blade.
- The Blade’s Geometry. Yes, that high school geometry class may help you a little bit here, even though you might not have thought so when you were studying it. It will have to do with the blade’s teeth (shape and angle), and kerf. The smaller blade might have a smaller kerf, so take this into consideration when measuring.
- Rotation Speed. Here, just make sure the maximum RPM of the circular saw is greater than that of the blade you are using. Again, with such a small difference in size in this article’s example, it won’t be an issue. But, it can be with a greater difference in size. The saw’s general performance can be affected – the larger blade will cover more distance per revolution than the smaller blade, suggesting less stress on the smaller blade – – exactly why you want the max RPM of the saw to be greater than that of the blade.
Can You Use A Larger Blade With Your Circular Saw?
This is not a good idea. The larger blade will put greater stress on the motor enough that it may not have the strength to give the blade adequate cutting power. A larger blade can tend to wobble, also, putting additional strain on the arbor. That strain could lead to the arbor failing with catastrophic results.
There is also the issue of the blade guard, which may not be able to accommodate a larger blade. The blade guard is there for a safety reason, and safety always comes first in the workshop.
Although we were unable to find a video directly on point about using a smaller blade size, we do have a couple of suggested videos for you about blades and circular saws that you might find helpful;
This video is all things circular blades.
This video demonstrates how to change the blade in your circular saw.
We always talk about the right tool for the right job at Obsessed Woodworking. In this instance, it’s the right blade for the saw. Always remember to be safe, and use your shop goggles when using your circular saw in the shop.