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| Forum topic by Don | posted 602 days ago | 1330 views | 4 times favorited | 14 replies | ![]() |
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602 days ago |
This is an article that has been worked around a bit and was in a woodworking club newsletter that I used to edit. I’m sorry that I can’t recall the origin of this article, but there is as much of me in it as the original author. I’m being up-front in stating that although I’ve modified it considerably, it is not all my work. However, it contains a lot of useful information for those of you that are new to the bandsaw. Have you ever notice how hard it is to rip a length of lumber on the bandsaw, especially a tall, thin piece (known as re-sawing)? You set the fence, previously aligned parallel to the miter slot. You set the width of the cut allowing a little extra for a pass over the jointer. Then you line up the wood against the fence and push. And pretty much without exception, especially on a long cut, it will either crawl away from the fence or bind against it, causing the blade to deform sideways away from the fence. The end result, in either case, is a tapered, irregularly shaped piece of work. This effect is usually exaggerated as you rip taller pieces. And it’s even more noticeable when you are ripping thin pieces, such as 18” veneer. It is usually devastating to your project, or else you cut extra thick to plane it true, wasting valuable timber. This is a 100% common experience with bandsaws. The basic reason is that the blade is not parallel to the miter slot. Several factors are the cause, including blade tracking on the wheel, wheel alignment and blade tension. In the ideal world we would tune these out. In reality it’s very difficult, and won’t stay for long periods. This inherent difficulty actually has a pretty easy ‘workaround’. The answer is “compensate”. Take a piece of 3/4” scrap at least 2’ long and about 4” wide with one clean, straight, and true edge. (Pass it over your jointer to achieve this.) Draw a line 1/4” from, and parallel to, the clean edge. Use a gauge if necessary, but the line must be parallel to the edge. Loosen the angle adjustment on the fence. You may have a factory fence that takes a wrench to set the fence angle. If not, you might want to build your own adjustable fence system. The photos of mine below show one approach; this one also has a tall re-saw fence. Slide the saw fence safely off to the left but keep it accessible. Start a freehand cut carefully guiding the timber through the blade along the line on the test board. Be smooth in your adjustments to follow the line. Don’t wander back and forth. In other words, don’t be swinging the board left and right to stay on the line. Make little corrections so that you ultimately establish a “cut path” before you run out of board. Cut slowly (at first) and continue until you get a cut that is tracking the line. About 3/4 of the way through the cut, or when you are sure you have established the track, holding the timber firmly, and turn off the saw. DO NOT MOVE the piece. Clamp it to the table in this exact position (or hold it firmly). Slide the fence against the clean edge and tighten the angle adjustment. With my shop-made table and fence this is easy. I simply loosen the front and rear knobs on the fence and adjust the angle of the fence to the wood. The front knob goes through a slotted hole that allows the fence to be adjusted at an angle. That’s the tracking angle for this blade, under this tension, at this particular time. I was skeptical, especially when I could see the offset angle. But I then cut a 2mm slice off a 15mm piece of timber 1m long. Awesome! I never knew the saw could perform so well prior to understanding this. You will have to do this setup prior to any bandsaw work if you have changed the blade, the blade tension, or the wheel alignment and it’s worthwhile checking the drift angle even if you haven’t. But the short time this takes is well worth the result. Here’s a shot of the underside of my bandsaw that shows how the larger table was attached to my Jet 14” bandsaw. -- CanuckDon "I just love small wooden boxes!" http://www.canterburybaptist.org/ |
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