There are always common issues that are a part of sawing that we can all relate too. One such issue is dealing with sawmill blades rising out of the cut. So today in this article we are going to look at some facts that I hope will help you when you have to deal with these ‘rising sawmill blades’.
Typically with a rising blade what you will see is the band enter the log and when it does, it will rise and then come back to settle in a straight path cut. Or when it hits a knot in the wood it will rise and again come back to settle into a straight cut. Note: if you have a vertical sawmill these rules equally apply.
Before I get to in depth with an explanation let me explain that figuring out why a bandsaw blade does one thing or another is not voodoo, nor is it magic. The fact that there is a Creator who has set physical rules in place, and that those physical rules are consistent allow us to take the facts and solve problems. So with that being said, we can continue to do the same thing and yield the same results, or we can make a change to get different results. And in this case we want to change the results.
Now let us consider the bandsaw blade that rises in the cut when hitting an adverse condition such as a wood knot. Let’s eliminate the two most obvious things that would cause a bandsaw blade to deviate in the cut: a dull tooth, and a bad set. But let’s say our blade is freshly sharpened with a tolerable set. With these two things being true we know that the blade has the ability to cut straight through the knot. But it doesn’t, so why? Here’s a hint; the tooth load increases as the wood becomes harder so the bandsaw blade is always going to travel in the least path of resistance based on the physical alignment of the sawmill and the flatness of the bandsaw blade.
You see the knot is just as hard ¼” of inch up as it is straight through it, so the sawmill blade is not ‘seeking’ softer wood. The blade does not have eyes or sensors to tell it where softer wood is located. But it’s the physical pressure points from the wheels and guides that direct the blade to the least path of resistance. You might say just like air flowing between two large buildings, the buildings are pressure points that direct the path of the air. Physical pressure points also control the physical activity of the bandsaw blade.
The more adverse the condition the more the sawmill blade will be driven to the least path of resistance. Adversity can come in different forms. For instance, pushing the blade fast, or pushing when dull and the thing to look for is the sawmill blades first reaction whether that be to rise up or dive down, and in this case we are looking at the rising blade.
Consider some physical conditions or some pressure points that control the outcome of sawing with a sawmill.
Here's an Exaggeration to Make a Point.
If I were to tilt the band wheels back out of square by 1 inch at the top of the band wheel away from the log or cant you would visibly see the sawmill blade angle up, or aimed up severely. If we then tried to overcome this adverse angle with the guides we would conclude that the sawmill guides could not overcome this much misalignment and we would all agree and guarantee that the blade would saw upward as a least path of resistance and would do so 100% of the time.
We can say with certainty that the guides can only guide a sawmill blade in a limited fashion and the limiting factor is how the band wheels deliver the band to the guides. Remember that guides should always aim the sawmill blade parallel with the travel of the head on the bed of the sawmill.
Now Another Exaggeration to Make it Stick!
If I were to tilt the band wheels forward out of square by 1 inch at the top of the wheel toward the log or infeed cant, you could visibly see that the sawmill blade is aimed down. If we then tried to overcome this adverse angle with the guides we would conclude that the guides could not overcome this much misalignment and we would all agree and guarantee that the sawmill blade would saw down as the least path of resistance and would do so 100% of the time.
Again we establish that the guides can only guide a blade in a limited fashion and the limiting factor is how the band wheels deliver the band to the guides.
Let's Consider a Rifle and the Sights.
If the sights are set correct and aimed at the bulls eye, yet the gun shoots 6 inches to the right at 100 yards, we would have to conclude that the barrel which directs the path of the bullet was pointed 6 inches off. We would then conclude quickly that the barrel must be realigned so the sights can be supported, then the path of the bullet can be expected to be exact with the sights. The redirection is absolutely necessary for accuracy.
Upon the correction we could guarantee that the bullet would hit the bulls eye when the barrel is held aiming at the bulls eye. If however, the barrel is not realigned with the sights the bullet will always hit 6 inches off at 100 yards. Proving again, to get the same results don’t change anything, but if change is desired you must change a physical condition. We also note the true line of the barrel will always send the bullet in exactly the direction it is pointed.
Think on this: The blade guides cannot overcome any significant amount of misalignment no more than the sights of the rifle can overcome a misaligned barrel. Ponder the application: The band wheels are the rifle barrel of the bandsaw blade and the guides are the sights.
More About Pressure Points.
For the band wheels to deliver the band to the roller guides in the most guidable manner, and I mean for the roller guides ONLY, these instructions must be followed:
We have found from experimenting that if the band wheels are tilted out of square by 1/8th of inch toward the log at the top, the roller guides can do the best job. This is because of the pressure points of contact of the blade with the guide. By tilting the wheels forward we lift the back of the band upward toward the barrel of the roller guide and this gives the guide greater control of the back of the blade.
If you can control the back of the blade you can drive the teeth in the intended direction. On the other hand, if the back of the blade cannot be controlled you cannot control the path of the teeth.
At this point we must remind you that blade flatness is of great importance. The band must be flat and we must know this and we should never guess about the flatness of a blade. Point being, I don’t want to guess about the flatness of a blade and start adjusting wheels or guides when the blade could be the problem.
Blade flatness works hand in hand with the alignment of the band wheels and if either the band wheels are mis-aligned or the guides are out of adjustment then having flat blades will not solve a cutting problem by itself.
If we want to have accurate results we must have accuracy with all things involved. I strongly recommend that each sawmill or grade resaw have their own roller and then you can improve your cutting by maintaining the flatness of your blade as well as maintaining the sharpness and set of the blade.
Remember, there are "3 keys to a blade" to obtain straight cutting. They are Sharp, Set, and Flat. But even when these are perfect they will not overcome a miss-aligned mill. If one of these is left out you cannot saw straight at good productive levels.
If you will apply these basics, you will find cutting perfectly straight wood is easy.
Now go make your adjustments, put on your new Super Sharp blade, and you will see why it is refered as the leader in band blade technology!
Cooks Super Sharp is taking the sawmill blade industry by storm! If you don't have a Super Sharp blade yet you are loosing money. Be sure to learn more about these remarkable sawmill blades. You can order them anytime, here online, through our online store.
Until Next Time,
aka... the "Saw Doctor"
Co-Owner CooksSaw.com
Leaders in Bandsaw Technology!
