Let’s talk a little more about the bandsaw this week.
Bandsaws can do things that table saws can only dream of, which makes them pretty much a necessity in a shop; however, they need to be set up properly and to do that one needs to keep a few things in mind.
Just to start with a proper definition, bandsaw “wheels” are the spoked or solid items/wheels that are mounted on the axles. Bandsaw “tires” are the rubber, or urethane, coatings on the rim of the wheels that the blade actually rides on. Typically, the tires can be removed from the wheels.
Most good bandsaws use a wheel/tire combination that is ‘crowned’. In other words, where the blade rides, the surface has a distinct ‘hump’ in it. This hump/crown allows the blade to be tracked (def: - centered on the tire) with much more precision than if the tire/wheel were simply flat. On the Delta 14” bandsaws that I am most familiar with, the wheel had the crown machined into it and the rubber tire was just flat rubber. When the tire was installed, it conformed to the crown of the wheel.
There are some ‘bandsaw guys’ that say the crown gives the operator the ability to adjust the blade to compensate for blade drift (our last week’s discussion), but in over 25 years, I never saw that as a workable option.
Setting up the blade tracking is not really a difficult thing, but like most adjustable items, one can wind up chasing their tail if they aren’t careful.
Tracking the blade first requires that you center the blade on the bottom tire and the top tire. Once you have the blade centered, blade tension should be applied. I like to start out with only ½ to ¾ of full tension, until the tracking gets fully set. Ok, the blade is on, the tension is set at ½ and the blade is centered on the tires. At this point, roll the wheels and see if the blade stays centered on the tires. If it does, go ahead and apply full tension and roll the wheels again. If the blade stays on and centered, you are probably good to go. If your initial testing shows the blade trying to creep towards the edge of the wheel, you will need to use the saw’s tracking adjustment to coax the blade back towards the center of the tire. When the blade stays close to the center of the tires, the saw should do its job just fine.
Next week we’ll have a lesson or two about proper Band Saw blade selection.
Send your questions or comments to:
Toolsmartz@bellsouth.net and we’ll see what we can do to help you.
Friday, September 23, 2011
Friday, September 16, 2011
V2.21 - Make a Straight Cutting Band Saw
Let’s go visit our old friend the bandsaw, this week. One of the most common problems with a bandsaw is getting it to cut straight. You start out with a nice straight line and start the cut and before you know it, the blade has decided that it wants to shoot off at an angle and destroy the part you did not want to cut. Some of the ‘old pros’ call this ‘blade drift’- I call it ‘don’t cut straight’.
Most often, here is what happens. Looking directly at the blade teeth, one notices that each tooth on the blade is bent out at a precise distance. This is called the ‘set’ of the blade. Having the teeth set outward provides clearance for the back of the blade to move through the work. It also provides some clearance for the blade to cut around a curve. However, if (for example) the teeth that are bent to the right stick out further than the teeth that are bent to the left, the blade will cut towards the right. The best solution to this problem is to purchase a high-quality blade, but I have even seen those drift sideways - right out of the box.
Another solution is to make the ‘set’ more equal - more balanced, if you will.
One way to do that would be to increase the bend of the teeth that are not sticking out as far; however, that is a very difficult thing to do. The more practical solution would be to slightly file the tips of the teeth that are sticking out too far- actually you would be ‘dulling’ them ever so little.
A method I have used is to hold a whetstone against the running blade and let the blade teeth lightly skim across the surface of the stone. A fine touch is a must, but with some practice, it isn’t hard to manage. Take your time and test the blade often by taking a test cut, so that you don’t dull them down too far.
Another thing that causes blade drift is when the number of blade teeth per inch is too high and the wood chips cannot escape from in between them. This typically shows up when doing resawing – sawing very thick wood – because the blade spends a lot of time inside the wood and can actually heat up and bow inside the wood, thereby causing a warped cut. The solution is simple: Use a blade with fewer teeth per inch.
Next week, we’ll talk a little about how to get your blade to track properly. It’s always a scary thing to be cutting along and POW! the blade pops off the wheels.
Send your questions or comments to:
Toolsmartz@bellsouth.net and we’ll see what we can do to help you.
_______________________________________________________________
Most often, here is what happens. Looking directly at the blade teeth, one notices that each tooth on the blade is bent out at a precise distance. This is called the ‘set’ of the blade. Having the teeth set outward provides clearance for the back of the blade to move through the work. It also provides some clearance for the blade to cut around a curve. However, if (for example) the teeth that are bent to the right stick out further than the teeth that are bent to the left, the blade will cut towards the right. The best solution to this problem is to purchase a high-quality blade, but I have even seen those drift sideways - right out of the box.
Another solution is to make the ‘set’ more equal - more balanced, if you will.
One way to do that would be to increase the bend of the teeth that are not sticking out as far; however, that is a very difficult thing to do. The more practical solution would be to slightly file the tips of the teeth that are sticking out too far- actually you would be ‘dulling’ them ever so little.
A method I have used is to hold a whetstone against the running blade and let the blade teeth lightly skim across the surface of the stone. A fine touch is a must, but with some practice, it isn’t hard to manage. Take your time and test the blade often by taking a test cut, so that you don’t dull them down too far.
Another thing that causes blade drift is when the number of blade teeth per inch is too high and the wood chips cannot escape from in between them. This typically shows up when doing resawing – sawing very thick wood – because the blade spends a lot of time inside the wood and can actually heat up and bow inside the wood, thereby causing a warped cut. The solution is simple: Use a blade with fewer teeth per inch.
Next week, we’ll talk a little about how to get your blade to track properly. It’s always a scary thing to be cutting along and POW! the blade pops off the wheels.
Send your questions or comments to:
Toolsmartz@bellsouth.net and we’ll see what we can do to help you.
_______________________________________________________________
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