What is a circular saw?

The circular saw is a tool that uses a toothed blade to cut wood. For this reason they are also often referred to as disc saws. And although some people sometimes refer to table saws as disc saws, in this blog when I talk about disc saws or circular saws I always refer to the portable handheld power tool that I talk about in this article.

Regarding the wood cuts that we can make with this woodworking and DIY tool, these can be: straight cuts along the grain (rip cuts); cross cuts at 90 degrees to the grain, angled cuts, or miter cuts relative to the wood grain; or cuts with the blade tilted. With a circular saw, we can only make straight cuts (well, except for some special techniques that we won’t cover here), but with the advantage that we can cut faster and even achieve cleaner and more precise cuts than with other machines like a jigsaw.

Let’s look at the different parts of a circular saw and the various systems they have to adjust to the cuts we need to make in each of our woodworking projects.

On the motor side of the circular saw, we have the plastic housing that protects the electrical parts, prevents us from touching the electrical parts, and contains the necessary elements to operate this electric saw during the cutting of wood or other materials.

1. Power trigger
2. Handle or knob
3. Unlock button
4. Circular saw motor
5. Access to change the brushes

The trigger is the button we press to turn on the circular saw. It is usually located on the underside of the handle.

The handle is used to hold the circular saw with one hand while pressing the trigger. Next to the handle, we usually have the knob, which is used to hold this power tool with the other hand. While cutting, we should always hold the saw with both hands, firmly and always attentive to any unforeseen events such as a possible kickback.

The unlock button is used to unlock the trigger so it can be operated. This prevents the circular saw from being accidentally turned on. Unlike the jigsaw, this button does not keep the trigger engaged.

The motor of the circular saw can be directly connected to the cutting blade or via a worm drive. The nameplate provides the power in watts and the rotation speed. The rotation speed is important to consider when installing a new blade, as cutting blades usually have a maximum speed limitation.

Over time, the brushes that carry the electric current to the motor wear out, so they may need to be replaced. To avoid opening the entire housing that covers the motor, modern saws typically have easy-to-open caps for simple brush replacement.

On the blade side of the circular saw, we have the parts that directly engage in cutting and some safety systems.

The circular saw blade has a hole in the center for mounting on the machine using a screw, and teeth on the outer edge for cutting wood. The central hole must have a diameter equal to the raised flange around which it must sit on our saw. Sometimes, when buying a blade for a circular saw, we also find adapter rings for different diameters. The teeth can be made of materials harder than the blade itself. Blades can have varying numbers of teeth, and the teeth can have different shapes, even on the same blade. The shape and number of teeth will affect cutting speed and cleanliness.

On some circular saws, we see a metal plate behind the cutting blade that surrounds a small portion of the blade, maintaining a few millimeters distance and following its curved shape without reaching the full depth of the cut. This riving knife maintains its position relative to the blade even if we change the cutting depth. It should have the same thickness as the blade and serves to prevent the cut in the wood from closing against the blade, thus reducing the possibility of kickback.

The bolt that keeps the circular saw blade fixed in position. It can be an Allen type or hex head. If it’s an Allen type, the circular saw usually comes with the necessary wrench to loosen and tighten the bolt. To prevent the blade from moving while loosening or tightening the bolt, it’s necessary to lock the blade, either with a piece of wood or by using the blade lock button that some of these power tools have.

When we want to change the blade of the circular saw, it’s necessary to lock the blade to tighten or loosen the screw that holds it in place. To do this, we can use a piece of wood to block the blade, or in some circular saws, we find a button that, when pressed, locks the blade. It’s also good to know which way to turn the tightening screw; if pressing this lock button doesn’t loosen the screw, we might need to turn it the other way. In direct-drive saws (see more below on types of saws), the bolt usually tightens clockwise (normal for all screws), but in a mini saw I have with a worm drive (see more below), the arbor bolt tightens counterclockwise.

To install the cutting blade on our circular saw, we must place it between two washers that fit on the drive shaft. The end of the drive shaft is more or less rectangular, so the washer that goes over the blade fits into that shape. Thus, the tightening screw presses this upper washer when inserted into the hole in the drive shaft. As for the other washer, the lower one, it’s very important when buying a new blade because the central hole of the cutting blade must fit perfectly on the circular flange we have on that washer. Some blades come with rings that allow the blade to fit different washer sizes. In some circular saws, this lower washer has a flange on one side and another size flange on the other side.

We can also have a washer for when the blade hole is larger than the mounting diameter on the arbor. So, often when buying a new cutting blade, we see that it comes with simple washers to adapt it to different models or brands of circular saws.

The lower guard protects the lower part of the blade and protects us from getting cut if we turn on this power tool when not cutting. I’m not sure if this guard will close quickly enough in the event of a kickback from the circular saw.

So, when we want to cut a piece of wood, as we approach the blade to the edge of the wood, the guard starts to open to allow the blade to make contact with the wood. This guard includes a tab to open it if necessary, if for any reason it doesn’t open on its own. For example, in cuts with the blade at 45 degrees, the lower guard often has difficulty opening, so we must use the tab carefully while starting the cut.

The upper guard is the rigid housing that surrounds the upper part of the cutting blade. It serves as cut protection and also guides the sawdust produced towards the dust extraction port located in the upper guard.

The dust extraction port is a small tube (or sometimes just an opening) that protrudes to the outside or to the rear of the upper housing. It serves to evacuate much of the sawdust produced when cutting wood. It also serves to attach a vacuum hose, although sometimes connecting a vacuum hose here can make working with the circular saw awkward and even dangerous. I’ll talk more about this in the section on circular saw dangers.

The metal base is what we rest on the wood to be cut (or on a guide in some cases), and it slides over the wood while cutting.

The depth adjustment system, at the back of the saw or on one side, is usually a wing nut or lever that we can loosen to lift the cutting blade relative to the metal base. We only need to loosen or tighten in one place because at the front there is a hinge that allows the rest of the circular saw to tilt forward relative to the metal base.

Similar to the depth adjustment system, we have a system for adjusting the tilt of the cutting blade. But in this case, we have two wing nuts that we can loosen to tilt the saw sideways relative to the metal base.

When changing the cutting tilt, we can use a scale that tells us the degrees of tilt, but it is not a very reliable scale, and it’s advisable to have another system to verify or adjust the angle. I usually use a plastic drafting square or architect’s square to check the 45-degree tilt angle.

In the metal base, we usually have a couple of slots to fit a typically metal side fence that we fix in the desired position. This allows us to make parallel cuts, usually rip cuts, although the fence is not usually of high quality.

These guides are grooves in the front of the metal base that align with the cutting blade. They help us follow the cutting line when cutting with the blade at 90 degrees or with the blade at 45 degrees.

These are saws with the blade directly connected to the motor shaft or through a straight gear system. Thus, the cutting blade rotates in a plane at 90 degrees to the motor shaft. The blade speed can be the same as the electric motor’s speed or determined by the gear transmission ratio if there is one. These are the most commonly used circular saws and are the ones we usually find in hardware stores in a wide variety of brands and models.

They are lighter than worm drive saws and are more manageable.

Worm drive saws are circular saws where the motor shaft drives a worm gear that turns a pinion gear, which in turn rotates the shaft connected to the cutting blade.

In these saws, the blade rotates at 90 degrees to the electric motor shaft. Since the motor is positioned parallel to the blade, these circular saws are usually longer and narrower. Being narrower and longer, they are useful in construction as they can fit into narrower spaces and allow for a few more centimeters of reach when extending the arm while cutting.

To transmit the motor’s power to the blade, a worm gear system is used. The worm gear is a spiral gear aligned with the motor shaft, or parallel to it, which turns a flat gear connected to the blade: the motor drives a worm gear that turns a pinion. This pinion turns the shaft connected to the cutting blade.

The worm drive configuration makes the blade spin slower than direct-drive saws (the cutting blade rotates slower than the motor), but in return, these circular saws have more torque. However, they are somewhat more challenging to handle.

I don’t have a “normal” worm drive saw, but I do have one of those mini saws that have recently become somewhat trendy (I don’t really see the appeal). These mini saws operate with a worm drive. The one I have, despite being small, felt very uncomfortable to handle. Additionally, being a cheap circular saw, it came with a rather poor blade that splinters the wood a lot. But from the image, you can get an idea of how the worm drive system works.

The traditional circular saws with their power cord. These are what I use in my small home woodworking shop since it’s rare for me to need to use the circular saw outside the shop or in areas where I can’t plug it into an outlet. They have the advantage that the battery doesn’t run out, and since I’m used to unplugging it after working, there is less danger of accidentally turning it on when I’m not using it.

Aside from safety, which we will discuss later, let’s see how to use an electric circular saw:

To cut strips or boards of wood with a circular saw, it’s advisable to clamp one side of the wood to be cut (we generally clamp the side of the wood on the motor side of the saw).

First, we mark the cutting line and adjust the cutting depth of the circular saw so that it does not protrude more than one tooth below the bottom of the wood being cut. This way, we achieve a cleaner cut and reduce the effect of kickback. Then we proceed to cut with the saw, holding the circular saw with both hands whenever possible.

A trick for clean cuts is to ensure that the good side of the wood is facing down. This is because of the way the circular saw cuts, it makes a cleaner cut on the bottom side of the wood, while it causes more splintering on the top side.

Another trick for clean cuts is to apply painter’s tape on the wood and draw the cutting line on top of it, as the painter’s tape will help contain the splinters produced when the blade, in its cutting action, pushes the wood upwards. But don’t expect this to achieve a perfectly clean cut.

My best trick for clean cuts in wood is to use a high-quality cutting blade with the circular saw.

Now we place the front of the metal base on the wood to be cut, turn on the saw before the blade touches the wood, bring the blade to the wood, and start cutting. We slide the metal base over the wood, making a straight cut until finishing. For miter cuts (e.g., at 45 degrees) or 90-degree cuts on narrow wood, it may be sufficient to cut freehand, but for wide boards, it is necessary to use guides that allow for straight cuts. These also help to cut more precisely.

When cutting a board with a circular saw, it’s necessary to use a guide for a straight cut. We also need a large surface to support the board. Here are two ways to do this:

a. I usually cut them on my workbench. I set my homemade guide for straight cuts with the circular saw, adjust the cutting depth so that only one tooth of the blade sticks out below the board, and firmly holding the saw with both hands, I cut the board. The problem with this method is that the cutting blade faces me, and the motor faces the inside of the board. Although I have experience doing this, it may not be the safest way to cut a board for beginners. If the piece of the board left on the motor side of the saw is small, then I don’t have this problem because I can cut at the edge of the table, remaining on the motor side.

b. Another option is to cut the board on the floor. Not directly on the floor, but on a rigid foam insulation panel, for example, and with the blade height adjusted the same way as in the previous case. We set the guide and cut the board. The advantage is that we can step onto the board, ensuring we stay on the motor side.

Always remember the dangers of these woodworking tools and never get complacent, as the circular saw is one of the most dangerous woodworking machines we will work with, and we must always be aware that a kickback can occur.

Coming soon.

According to what I find on the Internet:

The bottom of the cutting blade should be about 5mm lower than the bottom of the riving knife.
The space between the teeth of the cutting blade and the edge of the riving knife should be about 5mm.

But I will try to find more information on this.

The main advantage of the circular saw, I would say, is the speed with which it cuts wood. Additionally, with good woodworking guides and a high-quality cutting blade suitable for the type of work we want to do, we can make perfectly straight cuts and cut wood very precisely and cleanly.

This woodworking tool will help us pre-dimension the wood, give it final dimensions, and even make precise cuts when cutting, for example, some slots for making woodworking joints.

The main disadvantage of the circular saw is that it is more dangerous than other electric saws like the jigsaw or saber saw.

Another disadvantage is that the circular saw is only good for making straight cuts, so it is not as versatile as a jigsaw.

High-quality cutting blades for circular saws are expensive, and we will find many cheap cutting blades on the market that give the impression of being high quality but make mediocre cuts in wood. Keep in mind that a good brand tool always comes with a blade from that brand. It will not be the best blade of the brand and won’t have many teeth for super clean cuts, but it will still be a quality blade that makes better cuts than cheap blades.

I suppose we’ve all read the manual for this power tool and its recommendations, right? 🙂 And whatever I say here or anywhere else should not be taken as valid if it contradicts what the saw’s manual or its manufacturer says in that manual or elsewhere. With that said, let’s look at some of the dangers I’ve encountered using this DIY and woodworking power tool. Although there are many things I haven’t covered here that you can find elsewhere, I will focus more on my own experiences.

The main danger of the circular saw is kickback. Although we will largely avoid this if we cut dry, straight, and flat wood, keep the cutting blade clean, adjust the cutting height according to the wood thickness, if the saw has a riving knife behind the blade, if we hold the saw securely with both hands, making straight cuts with the help of a guide, and are attentive to any strange movements of the saw.

Keep in mind that a rip cut (parallel to the wood grain) is more susceptible to causing kickback.

Do not use a circular saw for gardening or felling tasks, nor cut green or resinous knotty boards.

We should also be aware of where the cable is before moving the saw to the position where we will start cutting.

For some tasks, it might be a good idea to connect a shop vacuum to the area of the housing that covers the cutting blade where the chips come out, but for some cuts, the vacuum hose can make handling the saw difficult, making it better to wear a mask. And glasses, better with glasses, although this woodworking tool doesn’t expel chips as dangerously as the router.

Also, circular saws are noisy, so it’s better to wear hearing protection.

As you can see, these circular saws can be dangerous power tools for beginners and even for more experienced users.

As you may have noticed if you follow this woodworking and DIY website and my YouTube channel, I’ve bought several circular saws over the years. I’ve worked with several brands, and my best recommendation is to buy a model that has a riving knife behind the cutting blade. Although it doesn’t eliminate kickback 100%, it helps to avoid it to some extent. And also, in this case, I would go for a saw of a good brand if we can afford it.

If we are looking for a cheap circular saw, we must think that it will likely not withstand intensive use but will be for occasional use. And remember, a cheap saw comes with a cheap blade that will likely make poor cuts. My experience is that high-quality cutting tools (blades, cutting discs, knives, etc.) make the difference in making clean and quality cuts.

That said, remember that a high-quality saw always comes with a high-quality blade. It won’t be the best in the range, but it will be suitable for many of the cuts we will make.

A cheap saw probably hasn’t undergone a good quality control process, making it more likely to arrive defective.

We should also consider what we will be cutting with our circular saw. Sometimes a mini saw is enough. But mini worm drive saws, to me, are not comfortable to handle. I would prefer a mini saw that is a smaller version of the typical direct-drive ones with the blade spinning directly with the electric motor shaft.

Corded or cordless? My first opinion is corded, as we will normally (in my case, 95% of the time) use the circular saw in the workshop, and it’s frustrating to run out of battery or have something break in the battery or its connections and have to leave a project unfinished. If we opt for a cordless circular saw, again, we need a high-quality battery.

Yes, I know I’m focusing a lot on buying a high-quality brand circular saw, but today we can buy affordable models for around €100. And a circular saw is a tool we will use for many years.