Short blade life
Band mill blades that don't last, burnt tips and bad bearings. December 18, 2001
Question
I've been getting great life out of new Mizer blades--400 bd ft or more--but after I sharpen them, I'm lucky to get 250. I grind as little as possible off the face and back, lightly dress the wheel every blade or two to avoid buildup, run plenty of water, and don't go very fast. I do get some black tips no matter what I do, other than going ridiculously slow. What's the deal?
Also, what about carbide blades? Is the extra life worth the extra cost?
Finally, on my Wood-Mizer I'm getting lots of play on the idle-side band wheel. This causes the blade to shimmy forward and back relative to the outer blade guide. Has anyone ever replaced whatever bearing that thing rides on?
Forum Responses
When I grind and the tips get black, it is the result of the stone being too aggressive as it passes up the back of the tooth. If the tips turn black, the tooth has lost its cutting life. You need to keep dressing the stone until the black does not appear.
We sharpen Wood-Mizer blades with no water, and we take at least a moderate amount off. I wonder if you are really getting the blade sharp. We can run about as long on a sharpening as we can out of the box. We do use a sharpening stone by Suffolk machinery--very, very hard. We have to dress the stone, but only occasionally. Our biggest problem is that the blade breaks after about 4 sharpenings. I suspect we need to take more off when we sharpen.
Sounds like you aren't getting the blade sharp. I get a little black on the blade from the stone being loaded and can stop it by passing the dressing stone over it lightly to expose new grit. You may be overheating the tooth, but you will see it turn red at the tip if you're watching closely. If you are using a heavy flood of water, there should be no problem. I sharpen sometimes without water and get away with it on a WM sharpener.
A good rule of thumb is to only face-grind enough to flatten the face to 90 degrees and then take the rest off of the back to sharpen it. If you are working with a damaged blade, you need to reshape both and the gullet.
Tooth height is important and is easy to ignore. It will cause you to lose life and will also act like a dull blade.
I have replaced the bearings in the idle wheel and it was no problem. A damaged v belt will cause the same symptom you describe as well as a buildup of sawdust under the drive side belt.
Check the idle bearing while tension is on the blade, to be sure. The wheel will be loose normally if the blade is removed, and a lot of folks mistake that for a bad bearing when it isn't.
Unless you are cutting something that your blade can't handle, like nails or other foreign objects, don't waste your money on carbide or other exotic tips. It's cheaper to sharpen a blade; and the body of the blade will break regardless of what is on the tooth. As a matter of fact, you will maybe get more life out of steel teeth because you will keep them sharp and decrease the strain the causes body breakage, whereas you would be tempted to run a carbide tooth even if it were dull because you couldn't sharpen it.
I used to sharpen my own bands and had the same problem with burning the tips. No matter how slow I went, they would burn. I was goofing around one day to see how fast I could sharpen a band, and the teeth didn't burn (until about halfway when the wheel lost its shape). I put on a good band and tried about twice the speed I was sharpening normally. I would get a burnt tooth once in a while, but not bad. It must have been that the wheel was in contact with the face of the tooth too long.
I am now trying a Cobalt blade. I normally run Timberwolf 1-1/2". I was getting about 500 feet to a sharpening and about 6 sharpenings. I started thinking about cost per board foot of the blade. I took the gamble of buying a $68 blade, which is twice the cost of my normal band. I am cutting hemlock, red pine, larch, spruce and some hardwoods. I put the blade on and ran 3,000 to 4,000 feet with it. I just used it the second time on dirty logs, and got 3,000 feet on it. It is going back for its third sharpening. So far it has taken the place of two complete lives on a normal band, and still going strong. One thing I especially like about it is the ability to go from white oak to red pine with the same band. I got the Cobalt blade from Suffolk. The whole blade is cobalt, not just the tip. It is actually made for exotic hardwoods and residential timbers (yard trees).
If you do need a new bearing, get the new upgraded version available now for older mills with the smaller type bearing. It's larger and should be the last one you'll need for a long time.
A friend just bought a Wood-Mizer with new blades. He asked me why the blades were failing with less than about 4 hours of time on them. I advised him to run the new blades at a slightly lower tension and he has had really good luck since.
When I sharpened our own blades, I found that I'd burn the tips every time if I went too slowly. I got to really speeding the pace up and making two light grinds - one kind of a hit and miss and the second to get face, gullet and top clean. Then I'd check the blade for sharpness and send it around one more time if it was sharp, sharp.
Why do you sawyers keep sharpening your own blades? You will save time and heartburn by sending the blades back to Wood-Mizer for resharpening. I sharpened at home for six years, then wised up and have been sending them back to Wood-Mizer now for five years. I typically get 800-1000 bd.ft. per sharpening and they last for 5 or 6 sharpenings. I've put 1150 hours on my latest Wood-Mizer, an LT40HDD40 hydraulic mill, with setworks and debarker. The Wood-Mizer debarker is worth more than its weight in gold. I change blades every 3-4 hours of cutting time. I also installed the latest guide rollers and the Lube-Mizer option, both excellent upgrades! I've noticed some Wood-Mizer sawyers get terrible results when using the all-purpose 10-degree blade on walnut/hard maple/white ash, because it dulls almost immediately. For those woods, you must use the frozen wood blade (9 degree hook angle) to get perfectly flat cuts and long cutting time.
400 blade sharpenings at $8 a hit= $3200. Not everyone runs their mill all the time, so if you have a little spare time, it is a great way to save money.
