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Last updated on June 29th, 2021
A miter saw, circular saw, cut-off saw, radial arm saw, and a table saw have one thing in common; they all use circular saw blades to cut. Each of these power tools uses a motor to rotate the circular saw blade at a high speed for cutting. Some common woodworking cuts you can make with a circular saw blade include cross-cuts, rip cuts, miter cuts, rabbet cuts, and bevel cuts. However, to make very clean and accurate cuts, you must always keep the blade sharp. This allows you to get through workpieces like butter. Otherwise, you may end up with ragged and ripped cuts. Sometimes a blunt saw blade may cause so much friction that may result in burnt cuts and a lot of smoke.
To avoid lackluster moments with your saw tool, always inspect the cutting blade thoroughly before making cuts. This will help know when the blade is dull or has a problem so that you don’t end up with bad cuts. You will also be able to replace or sharpen the blade ahead of time. Furthermore, a sharp saw blade that is free of defects will extend the life of your saw.
Identifying a bad or dull circular saw blade
Identifying a blunt or dull circular saw can be a walk in the park if you know how to read the signs on the blade or the workpiece. Unfortunately, not everyone knows how to do it. Only the seasoned woodworkers find it easy. Others find it difficult and even complicated to differentiate when a saw blade needs replacement or sharpening.
Luckily, there are some key telltale signs of a bad circular saw blade you can identify easily. These signs can help you decide whether to sharpen or replace the blade on your cutting tool. In this article, I will share with you the 10 most common signs of a defective circular saw blade. These signs will help you decide if your teethed blade needs sharpening or replacing. Knowing how to identify the signs will also help you plan your next woodworking job more effectively.
10 Common Signs of a Bad Circular Saw Blade
The following signs will help you identify a defective circular saw blade so that you can replace it in time. You will also learn how to identify a blunt blade that only needs sharpening.
1. Blade starts chipping wood
Chipping or tearing out of wood occurs mostly when cutting across the grain direction of lumber or sheet of wood or plywood. As the saw blade exits wood material, it lifts up little pieces of the wood grain. This causes the wood material to splinter at the cutting point resulting in ugly edges.
Although chipping of wood is one of the characteristic signs of a blunt saw blade needing replacement or sharpening, it can also be a sign of lumber or plywood in a bad position. Therefore, before you decide to slap in a new round saw blade, you need to ensure that you are using the woodcutting best practices.
One of the best practices of cutting across the grain of wood material is to scribe the cutting line before running the saw. You can use a utility knife or a cutting gauge to scribe. By scribing or precutting wood with a scribing tool, you savor fiber ahead of time so that when a sharp saw blade cuts, you have a nice clean edge. Alternatively, you can apply masking tape on the top side of the wood that will be cut.
Another trick that applies mostly to plywood is to cut with the best side facing down. This way, you prevent the teeth of the blade from grabbing and tearing out the veneer when exiting. Otherwise, if you are still getting ugly rough edges, I would advise you to sharpen the saw blade or replace it with a new one. Torn-out wood edges are ugly and unprofessional. Don’t let a dull blade undermine your woodcutting skill!
2. Blade cuts with difficulty or binds
Unless your electric wood saw tool is not powerful enough, one of the surest ways to tell that a cutting saw blade is blunt is if it struggles to cut through the material. You will also notice that it takes longer to cut, requiring you to apply a lot of force to push it through the cut.
A good circular saw blade cuts through like butter. If yours isn’t or bind up, you need to sharpen it or get a new blade altogether.
3. The cutting blade spins slowly while cutting
As it gets harder to cut through wood with a dull saw, the speed of rotation of the blade reduces significantly. When a saw blade spins very slowly, it causes friction to build up, making it extremely difficult to cut through. A blunt blade cuts very ineffectively and may degrade the quality of your woodcuts with burn marks. It may even cause the motor to labor a lot, resulting in overheating. And you know that when you overheat the motor of any tool, you shorten the life of that tool.
Although a blunt blade is a major cause of slow spinning, using the wrong saw blade can also cause it to cut through slowly. For example, a cross-cutting blade spins very slowly when used to make rip cuts. Therefore, you should make sure that your circular saw, miter saw, or table saw has the right blade for the type of cut you want to make.
4. Saw produces laboring sound when cutting
In addition to spinning slowly, a dull saw blade may also cause the tool to labor as you cut through wood material. If this happens, the motor and the blade may overheat causing your wood to smoke and the motor to smell like it is burning. A burning motor smells like overheated car brakes.
However, the laboring sound of a saw motor does not always indicate a blunt blade. Sometimes the sound may be produced if your saw comes into contact with wood material before getting to full speed. It can also occur when you start the saw while the blade is in contact with the wood you want to cut.
Notwithstanding the cause, a laboring sound is usually a sign of a saw that is struggling to cut. Detecting this sound, however, requires a trained ear to tell when the machine is working harder. Newbies might not differentiate and it would be advisable to look at visual signs such as smoking or tearing out.
5. Cuts become ragged and burnt
As mentioned, an unsharpened saw blade will not only cause the motor to overheat but also the blade due to the buildup of friction at the point of contact. This results in ragged cuts with burn marks. Marks of burning on woodcuts are very visible and make your work look ugly and unprofessional. You can avoid them by ensuring that the circular saw blade you are using is sharp enough to cut through wood easily and quickly.
There are other reasons why wood would have burn marks on it when cutting with a saw blade. One of the reasons is a dirty blade. The teeth of a circular blade must remain shiny. So, when they start to discolor, that is dirt building up and will cause friction to build up when cutting. This results in burn marks on lumber. You can avoid having dirty blades by cleaning regularly with a tool cleaner fluid for removing wood resin and a soft brush such as a toothbrush. This will keep the blade shiny and cutting as good as new before it gets dull.
On a table saw, the circular blade might cause burn marks on wood if you feed the stock too slowly or if the table saw fence is misaligned. So, you must ensure that you are feeding lumber at the right speed and that the fence is parallel to the table saw blade.
6. Workshop smells burnt wood
Sometimes it is easy to mistake small burn marks with wood contours. If you doubt that the dark edges are a result of burning or heating, you can validate with the smell of burnt wood. Usually, when wood overheats due to friction, dark areas are formed at the point of contact and a burning smell is produced. This smell is close to that of toast. When you smell it, you should know that your wood is cooking and it is time to check the blade.
7. Blade produces smoke while cutting
If you are wearing a dust mask, it might be difficult to smell burning wood. But you cannot fail to see smoke when it appears. And it is not usually good news when smoke comes out of your wood when cutting.
The heat due to friction between wood and a blunt saw blade produces visible white smoke. This is a sign that your saw blade needs your attention. You don’t have to wait until you cannot see the cut clearly to sharpen or replace the blade.
Other reasons the saw might produce smoke
Sometimes smoke will not necessarily mean that the blade is bad or blunt. It could be that you are cutting wet lumber. Wet lumber produces a lot of heat due to friction, which in turn produces smoke. So, it is good woodworking practice to always ensure that your lumber is dried well before cutting with a circular saw blade. Otherwise, it will be smoky and with casualties due to potential kickbacks.
Another common reason why you might see smoke coming out of your wood while cutting is if the saw is backward. A circular saw blade installed backward burns through wood more than it cuts. Hence producing a heck of a lot of smoke. This is a common mistake most newbies do when replacing or installing the blade for the first time. Some siding installers also place their blades in reverse to cut siding and soffit panels more easily. However, with wood, reversing the blade can be catastrophic, let alone smoky.
So, always inspect the circular blade on your saw before you start cutting wood to ensure that it is sharp, has all teeth, and is not installed backward.
8. Degraded cut quality
Woodcuts made with dull saws are rough and very ugly. The feel of the cut by hand will tell you that something is not good with the blade. But you also need to ensure that the wood material is properly positioned while you make cuts to avoid making a bad saw cut with a good saw blade.
9. Blade has worn teeth that can no longer be sharpened
After intensive use of the blade, the teeth will eventually wear out to a point that they cannot be sharpened anymore. How you tell that the blade is worn is if the teeth cannot In such a case, you need to replace the blade with a new one. Otherwise, sharpening a totally worn-out circular saw blade will not have substantial results.
10. Circular saw blade has a missing tooth
Sometimes when cutting with a circular blade saw you may encounter hard surfaces that may break the teeth of the blade. Dropping your saw blade on a hard surface may break the saw teeth, especially for tipped teeth. When you have such a blade, the only thing you can do is replace it with a new one. Otherwise, installing a blade with a broken tooth or chipped teeth on your saw machine may cause injury and often results in substandard woodcuts.
Pro tip: Instead of tossing the broken blade into the bin, you can make a fancy tool from it. Many tradesmen make steel knives from damaged saw blades instead of throwing them away.
Bottom line, if you want to maintain crisp and clean cuts on your wood, you need to know when the saw blade starts to fail. This will help you sharpen or replace the blade ahead of time before the quality of the woodcuts begins to degrade. To that end, the 10 factors will help you a great deal identify when the blade in your sawing machine starts to give up so you can act accordingly.
That being said, sometimes the problem is not a dull blade but rather a dirty blade. A dirty saw blade cuts horribly and causes chip-out to occur on the edges of your stock just as bad as a blunt blade does. It also leaves burn marks on wood, which affects the quality of cuts. Luckily, cleaning the blade using any of these 5 most effective ways to clean saw blades can eliminate the problem.
Lastly, if there is a symptom of a bad saw blade I have missed, please feel free to share it in the comment section. It will help everyone to keep their circular saw tools in optimal conditions throughout.