Now, before you start sharpening, it's a good idea to clean the circular saw blade first.

Next, take a small piece of wood not more than 5 inches long and 3 inches wide.

Stick sandpaper on the piece of wood.

Next, carefully remove the saw blade from the circular saw.                                     

Take the dull saw blade and, using a clamp or a bench vice, fix it in place.      

Mark the first tooth before sharpening beings, so you'll know when one full pass has been completed.                                                                                                       

Apply some oil or lubricant onto the sandpaper.                                                      

You don't have to sand the top of the tooth.     

Place the sandpaper on the face of the tooth and begin filing back and forth on the face of the tooth.              

After filing around 5 to 10 times, you can move on to the next tooth. 

Continue this process until all the teeth have been sharpened. 

With this step, you have successfully completed sharpening a circular saw blade.