Bandsaws are terrific tools to use, and can be very versatile in cutting wood. But for a bandsaw to be at its best, it needs a sharp blade. Many problems with using a bandsaw can be traced to using a blade that is too dull for the task at hand.
When a bandsaw blade becomes dull, you could replace it with a new one, but sometimes you can get some additional life out of your old bandsaw blade by resharpening it. This may seem like a daunting task given how many teeth there are to deal with, but this task is easier and quicker than you may think.
Today, we will learn how to sharpen the teeth of a bandsaw blade.
One thing to mention before getting started: this approach does well for carbon steel and bimetal bandsaw blades. Do not use this method with carbide or carbide-tipped bandsaw blades, as the teeth are too hard to sharpen easily. In the case of carbide-tipped bandsaw blades, the tip may even pop completely off while doing this procedure.
Bandsaw tooth geometry
Not all bandsaw blades are amenable for resharpening, especially if the teeth of the bandsaw blade is too fine. Luckily, the workhorse blade for bandsaws is a 1/2” 3 or 4 TPI blade (see our post on choosing a bandsaw blade), and the teeth on these blades are large enough that you can sharpen them easily.
When a bandsaw blade cuts, the sharp leading edge of the tooth slices through the wood. This is the part that becomes dull over time, and this is where we will concentrate on the sharpening. The sawdust that is made by the tooth goes into the gullet, which is the space between the teeth, and is eventually carried out of the kerf.
If the teeth are dull, however, it will not slice well, and it will not be able to cut its own path through the wood. Instead, it will follow the path of least resistance, and can be deflected by the grain lines in the wood, heading into softer areas of the board. Also, the pieces of sawdust tend to be larger if cut with a duller blade, and fill up the gullet faster. When the gullet becomes packed with sawdust, the sawdust surrounds the tooth and it can no longer cut, causing the bandsaw blade to follow the path of least resistance again and a deflection of the blade.
Sharpening the back of the teeth
Now we can start sharpening.
Here are the tools you’ll need:
- Blue masking tape or a Sharpie marker
- A Dremel tool
- A sharpening tool with a flat surface, such as a diamond plate, an oilstone or a waterstone.
One of the keys to a smooth and efficient cutting blade is to ensure that the tips of the teeth are all in the same plane. To this end, we will start the sharpening on the back side of the teeth. This way, if too much metal is removed, it won’t throw off the geometry of the front side of the tooth too much.
Before you start, make sure that the bandsaw is unplugged, so that it can’t be accidentally started while you sharpen the blade. Mark the bandsaw blade with some blue tape as seen in the photo above, or use your marker to make a mark on the blade. We will be working our way around the blade as we sharpen, so when the mark reappears, you will know you are done. If you don’t have anything handy to mark the blade, you can always look for the weld.
Next, pick a Dremel tool attachment that fits the curve of the gullet. Turn the Dremel on, and lightly touch the back side of tip of the tooth. Try to remove the smallest amount of metal that you can. It doesn’t take that much to sharpen the tooth. Making sure that the Dremel is on a low speed will help you maintain control.
Once you’ve done this, move on to the next tooth and repeat this process. Work your way around the bandsaw blade, and when you get back to your mark, you know you’ve hit every tooth.
Sharpening and aligning the front of the teeth
Now take your sharpening tool (diamond plate, waterstone, or oilstone) and place it so that it is facing the bandsaw blade. Open up the top wheel compartment. Move the sharpening tool slowly towards the blade until it barely touches the front of the tooth. Spin the upper wheel so that the blade is traveling backward, upward through the guides.
As the blade travels, any teeth that are protruding too much will contact the sharpening tool and be worn down a little. This will guarantee that the front tips of all the teeth are in the same plane, which means that each tooth is contributing to the cut, which leads to a smoother, more efficient cut.
If some teeth are touching the sharpening tool, but others aren’t, this means that the fronts of the bandsaw blade teeth are not aligned. If this happens, the teeth that are more forward are doing the majority of the cutting, while the teeth in the back slack off. Evening up the fronts of the teeth ensures each tooth contributes to the cut, which is more efficient.
Like in the first part, rotate the upper wheel until you see the blue tape come all the way around. When you’re done, you will have a newly sharpened bandsaw blade. Don’t worry about doing a less than perfect job. Just keep in mind that a poorly sharpened bandsaw blade will still cut better than your old dull one.
You should be able to get two or three sharpenings out of a bandsaw blade with this method. After that, it’s time to get a new one. And if you mess up the bandsaw blade, that’s okay, too. Remember, you started out with a dull blade that didn’t cut well, so there was nothing to lose by trying to sharpen it. But if things go well, and they should, you’ll have a bandsaw blade with new life.
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