Sharpening bandsaw blades

"Life is too short to be sharpening your own bandsaw blades" is what a co-worker who is also into woodworking remarked when asked him if he sharpens his own blades. I was inclined to agree with that statement until I hit a staple with a nearly new bandsaw blade. A very frustrating experience, having a good blade instantly transformed into a crappy one. Worse yet, my last blade had suffered a similar demise with a pair of small nails. So I had an urge to try to make right what I had screwed up without just throwing money at the problem again.

My first attempt at sharpening bandsaw blades was just to go at it with a cut-off disk on a Dremel tool and the blade still in the bandsaw.I was able to get the blade sharper than it was before, but the sharpened blade ended up making a wavy sort of cut in the wood. It was also hard to focus on the blade and cutter without another reference nearby, and I often ended up nicking the corners of teeth that I had just sharpened. So I figured perhaps this was not the best way to sharpen a bandsaw blade.
Why the red lines on the drawing? Well, you can't always assume people read the text, especially because I get a lot of traffic from non-English speaking countries, so I wanted the photo to make it obvious that I don't recommend it.

To start over again, I held a sharpening stone against the tips of the teeth for a few seconds with the blade running, so that they'd all be flattened a little to a consistent height. If your blade is inconsistently dull, perhaps as a side effect of cutting a nail or a staple, this may be a good idea. But if your blade is just dull from regular use, this step might not help any.

The next step was to rig up a setup for grinding the teeth. It had to be a one that I'd be comfortable sitting at. My rationale was that the more comfortable I was while sharpening the blade, the less tiring it would be, and I would end up doing a more consistent job of it.The wide piece of wood towards the center has a slot cut in it that the blade sits in. The smaller piece on the right also has a slot in it to guide the blade. With this setup, I can just slide the blade along to get at more teeth. The piece of wood at an angle on the right is another guide that helps to line up the blade as I pull it to the left.

I pulled up a chair to the workbench to do the sharpening. My 6 tooth per inch blade has over 550 teeth on it, so that's a lot of teeth to sharpen. But it was manageable.For resaw blades with fewer teeth, resharpening makes much more sense. For really fine blades though, hand resharpening may not be a worthwhile activity.

To sharpen the teeth, I just briefly touched the cut-off disk of the Dremel tooth to the top of the tooth. The Dremel tool is held at a slight angle so that the top of the cut has a slight bevel with respect to the direction of the blade's travel. Having previously flattened the tops of the teeth with a stone, all I need to do now is add a slight bevel to the top.Once I got a routine going, I was able to sharpen more than one tooth per second, so that sharpening all the teeth on my blade took less than 10 minutes. With that sort of time to sharpen a blade, it takes more time to go to the store and buy a new one. So the "life is too short to sharpen your own bandsaw blades" statement becomes difficult to rationalize.

Here's what the sharpened teeth look like. I made no attempts at grinding the valleys between the teeth.

I figure this procedure is good for only a few sharpenings before the blade needs replacing. With each sharpening, the teeth get a tiny bit shorter. To get a lot of sharpenings out of a blade would require deepening the valleys between the teeth. But once you do that, you also need to worry about the set of the teeth.Alternate teeth have a light left or right bend to them so that the cut that the blade makes is a bit wider than the blade itself. You can just see the left and right bend from looking straight on at the blade in the close-up photo at left.
With the cut slightly wider than the blade, the blade itself has a bit of room in the slot it cuts. This allows it to run freely without binding. It also gives the blade a little bit of slack so that it's possible to make curved cuts.
I figure once a blade has been sharpened enough times that it would be necessary to deepen the valleys and set the teeth, it's probably time to get a new blade. I'm happy extending the life of my blade by three or four times with resharpening, but I don't need to make them last forever.