10 Signs Your Circular Saw Blade Needs Replacement

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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 has a motor assembly that rotates the saw blade at a high speed enabling it to cut. Some of the common woodworking cuts you can make with a circular saw blade include cross-cuts, rip cuts, miter cuts, rabbet cuts, and bevel cuts among other 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, resulting in burnt cuts and a lot of smoke.

To avoid lackluster moments with your circular saw tool, you should make it a habit to inspect the saw blade thoroughly before making cuts. This will help you identify bad signs of a circular saw in advance to avoid transferring them to your cuts. By so doing, you will also be able to replace or sharpen the blade ahead of time and increase productivity. Furthermore, a sharp circular saw that is free of defects extends the life of your tool.

Identifying a bad or dull circular saw blade

Identifying a defective or dull circular saw can be a walk in the park if you know how to read the signs on the saw or 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 circular blade needs sharpening or replacing. Knowing how to identify the signs will 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.

How to identify a dull circular blade – 10 signs
  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 o wood is one of the characteristic signs of a blunt saw blade needing replacement or sharpening, it can also be a sign of a badly positioned lumber or plywood. 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. By scribing wood or precutting it using 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 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. Cutting wood becomes hard

    Unless your electric wood saw tool is not powerful enough, one of the sure ways to tell that a cutting saw blade is blunt is if it struggles to cut through wood material. You will also notice that it takes longer to cut and you have to apply a lot of force to push it through the cut. A brand new circular saw blade cuts through wood like butter.

  3. The cutting blade spins slowly

    As it gets harder to cut through wood with a dull saw, the speed of rotation of the blade reduces significantly. When the blade spins very slowly, it can cause friction to build up making it extremely difficult to cut through. A blunt blade is very ineffective and may degrade the quality of woodcuts by leaving burn marks. It may even cause the motor to labor a lot resulting in overheating. Overheating the motor reduces the life of the 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. Laboring sound

    In addition to spinning slowly, a dull round saw will cause the tool to labor you cut through wood material. If this continues, the motor and the blade may overheat. Sometimes a laboring sound may be produced if the saw contacts material to be cut before getting to full speed. It can also occur when you start the saw with the blade against the wood to be cut. A laboring sound is usually a sign of a saw that is struggling to cut. Detecting a laboring 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.

  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 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. Smell burnt wood

    Sometimes it is easy to mistake small burn marks with wood contours. If you doubt that the dark edges are as 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 inspect the blade.

  7. Smoking blade

    If you are wearing dust mask, it might be difficult to smell burning wood. However, you cannot fail to see smoke when it appears. Sometimes the heat due to the friction between wood and a blunt saw blade may produce visible white smoke. This is a sign that the blade needs your attention. You should not wait until you cannot see the cut to sharpen or replace the cutting saw blade.

  8. Cut quality degrades

    Woodcuts made with dull saws are rough and very ugly. A feel by hand will tell you that something is not good with the blade. But you also need to ensure that you have positioned wood material in the correct position while you make cuts.

  9. Blade can no longer be sharpened

    After intensive use, the teeth of your saw will eventually wear out to a point that they cannot be sharpened anymore. In such a case, you will need to replace the blade with a new one. Otherwise, sharpening totally worn-out circular saw teeth will not give you clean woodcuts. Sometimes if getting a professional sharpening service is impossible, it is best to buy a new sawing blade for your machine instead of trying to sharpen it yourself. You know the work of sharpening saw blades requires attention to detail for you to get substantial results. In fact, I recommend using a digital sharpening device if you are going to sharpen your saw blade. This ensures that you get a factory equivalent sharpening job, especially on carbide-tipped round sawing blades. If that is not possible, you better invest in a new blade altogether.

  10. Missing teeth on the circular saw

    circular saw blade with broken 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 also result in broken saw teeth, especially for tipped teeth. In such situations, the only thing you can do is to replace the blade 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.

    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 woodworking cuts, 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 cuts begins to degrade. These 10 factors will help you a great deal to identify when the blade in your sawing machine starts to give up so you can act accordingly. Lastly, if there is a symptom of a bad saw blade I have missed, please feel free to share it in the comment section. This will help to keep the circular saw tools in optimal conditions throughout.

Julius

Julius is an electrical engineer working as an O&M supervisor at a solar microgrid company. He heads a team tasked with maintaining operations of microgrid power plants. In his career, Julius has learned that getting the right tools for the trade is key to getting the job done right. That is why he likes to talk about tools.

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