How to sharpen a circular saw blade – 3 methods

Is it worth sharpening a dull circular saw blade? Find out in this article including three methods of how to do it.

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The secret to making clean cuts with your circular saw blades is keeping their teeth sharp. You can achieve this by either cleaning, sharpening, or replacing the blade whenever you notice it is blunt. In case you do not know how to tell a saw blade is blunt, read my article on the signs of a dull blade. You will find 10 common signs of a blunt or bad blade on both the saw blade and resulting woodcuts. In this post, however, my focus is on how to sharpen a circular saw blade.

Is it worth sharpening circular saw blades? I know that is probably the question running in your mind and the simple answer is that “it depends on the type of blade”. If you are using an expensive blade (above $50) you can sharpen it once or twice before disposing of it. But if you are using cheap blades, sharpening might be more expensive than replacing. So, the decision is yours to make.

There are many ways to maintain a sharp cutting edge on your blade teeth. You can sharpen the teeth by hand using a saw file, or angle grinder saw blade sharpening jig, or by sending the blade for professional sharpening. In the next sections, I will look at the three blade-sharpening options in more detail. I will also share the pros and cons of each to help you make the right decision about dealing with dull circular saw blades.

1. Circular saw blade sharpening by hand

Sharpening a circular saw blade by hand at home is the easiest and cheapest of the three options. All you need is a flat fine grit (600) diamond file and a vise for holding the blade firmly. But before you start sharpening, inspect the blade to make sure all the teeth are intact and none is chipped. Otherwise, you may have to throw away the blade and get a new one because it is unsafe to work with a chipped blade. If all is good, follow these simple steps to sharpen the blade.

Procedure

  1. Set up the vise on the edge of your workbench
  2. Install two wood pads between the jaws of the vise the install the blade and clamp it down. The wood pads protect the saw blade from being damaged by the metallic jaws of the vise.
  3. Grab your flat fine grit diamond file and get ready for the job. I am assuming your blade has carbide teeth.
  4. Mark the first tooth where you want to start from.
  5. Place the flat side of the diamond file onto the front of the carbide tip of the marked tooth.
  6. Make 2 to 3 light strokes with the file. This should put the edge back on the tooth.
  7. Repeat the process for all the teeth on the blade.

This method is the easiest for putting the edge back on your saw teeth. It is also inexpensive but tedious. It is also not very effective because you only polish the face of the tooth and leave out the other parts.

2. Circular saw blade sharpening using an angle grinder

This method uses a power tool to sharpen the saw teeth instead of a saw file. It is faster than the first method but you need to get the setup right. Otherwise, you might cause irreversible damage to your saw’s teeth.

First off, you need to get an angle grinder and a diamond wheel for the grinder. It is a bit expensive but it does a decent job restoring the cutting edge to the blunt carbide tips. You will also need a few screws and some wood pads. Here is how to set up the whole blade sharpening system and sharpen the blunt blade.

Procedure

circular saw blade sharpening jig
  1. Mount the angle grinder firmly onto a 2ft x 3ft wood pad or board. You can use plywood or MDF board.
  2. Ensure the grinder is parallel to the length of the board, a few inches from the edges. Mount it such that the grinding wheel is perpendicular to the board.
  3. A few inches from the other end of the board, mount two rails for mounting the second board.
  4. Mount 2 runners onto the second board. The board should be about half the length of the bottom board.
  5. Stack the two boards by the rails and runners. Now the boards are stacked such that the top one slides freely back and forth on the rails.
  6. Place the blunt circular blade on the top board near the edge closer to the grinder.
  7. Slide the top board such that the grinder wheel enters the groove between the teeth of the blade without touching the bottom of the gullet.
  8. Mark the position of the arbor hole on the top board and drill a hole for installing a bolt. This is the bolt onto which you will install the blade.
  9. Once you drill the hole, install the bolt, washers, dull blade, and a nut to secure the blade.
  10. Slide the top board such that the grinder wheel only touches the front of the carbide tooth and not the bottom of the gullet.
  11. Install a stopper on the bottom board to keep the top board from sliding past that point.
  12. Now adjust the angle of your grinder according to the incline of the teeth to ensure the wheel sits flush on the phase of the carbide tip.
  13. Mark the tooth and turn the grinder on to start grinding. Grind each carbide tip for 3 seconds and move on to the next.
  14. Work your way through all the teeth by sliding the top board back and forth and turning the blade clockwise to move from one tooth to the next.
  15. Grind until you reach the tooth you marked. By now your saw should have the edge back.

Alternatively, check out this link for sketchup templates for building a professional circular saw sharpening jig.

How to build a DIY angle grinder circular saw sharpener.

This method has a steep learning curve. It involves building a saw sharpening jig, which is not the easiest of tasks. The margin for error on this method is very slim since it uses a powered tool to grind the teeth. So the chances of destroying the saw teeth are very high for a beginner. However, the jig makes the process of sharpening the teeth by yourself very fast especially if you are dealing with a bunch of blades. This method is good for saw experts.

3. Sending the blade to a professional blade sharpener

Sharpening a circular saw blade can be difficult at times. You can also ruin the teeth if you are not careful. That’s why I would recommend sending dull blades for professional sharpening on a digital sharpening machine. The machine will not only polish the face of a blade tooth but also the cheeks and the top at the proper bevel angle.

The downside of professional blade sharpening on a digital machine is that it is not cheap. You will pay roughly $20 for a blade, making this option ideal for only the expensive blades. Otherwise, it is more economical to replace cheaper circular blades than to take them to the shop for professional sharpening.

Sending blades for professional sharpening is the easiest and the most effective of the three blade sharpening methods. This method has no learning curve. All you need is a fat wallet to pay for each blade, making it the most expensive, nonetheless.

There you have it! Those are the three options for dealing with blunt circular blades. Now you can make a decision on what to do with your worn out blades. If they truly cannot be sharpened, you can make beautiful utility knives instead of throwing the blades away.