Straight cuts through knots
I have a Kasco mill and am having trouble cutting straight in pine. I have tried different sets and hook angles but don't seem to be getting it right.
I have cut red pine on my Breezewood bandmill with very good results.
I use a blade with 8-degree hook and .019 to .020 set. The blade must be sharpened with the tooth tips square to the blade body, not to the set tooth. Sometimes I have to slow my feed rate slightly to keep the blade cutting straight.
Also, use a lot of blade lube to keep the pitch from gumming up the blade. And a lot of pith on the blade will sometimes turn or angle the blade as it goes through the guides making the blade rise or dive in the cut.
Woodmizer has a .055 blade that they say will do well on pine.
First off make sure your blade is sharp and set right, and use a new blade. Then I'd try slowing down for each knot, or keep a steady, SLOWER speed than you've been using. It's easy to get a head of steam going in the clear soft wood, but if you don't slow down for a knot you make a wave. If slowing down doesn't work, check your guide rollers to make sure they're holding the blade parallel to the bed.
What happens when you hit a knot while sawing is that the feed speed is fine for the lower density "unknotty" wood, but when you hit the knot, the density increases substantially.
The blade will find it easier to take a smaller cut (uses less energy that way), so it will try to go sideways. Even though a sharp blade is critical (and judge the sharpness by the side corners of the teeth), if you increase the feed with a sharp saw, then, when you hit the knots, you are in the saw boat -- sawing too fast (or not enough energy to cut the dense knots). So slow down!
It is critical that the saw have as much tension on it as possible, and a wider saw will do better because the back of the blade will help steer the blade straight. A thicker saw will go straighter, but the bending around the wheels is more difficult. Finally, keep the guides as close to the wood as possible.
I have a Hudson bandmill and use Woodmiser 1-1/4 x .042-inch bands, with their standard 7/8-inch pitch and factory hook and set. I sawed almost 2,500 feet of red pine last summer for a customer without any problems.
My mill is manual, so I'm adjusting the feed rate by watching where the knots are and listening to the sound of the engine. I used water as a lube with liquid dishwashing soap added.
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