How To Adjust or Tune A Bandsaw Blade
The Bandsaw Balancing Act Part 1
The following article was originally published in Wood News Issue 21,
Summer 1988.
For the past year, a renewed interest in the bandsaw as a woodworking machine has been evident through out the woodworking community. A catalyst for this seems to be Jim Cummings article "Home Shop Bandsaw" in Fine Woodworking #63 (March, 1987). From the hundreds of bandsaw owners I've talked with since the article appeared, it seems there are lingering questions on how to adjust a bandsaw blade, the blade choice and operation. In this article I will answer some of these questions by offering an approach based on practical results as well as theory.
My strategy for achieving good results on a bandsaw includes the following:
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Understand how the blade functions as part of the overall machine, and how to align it.
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Use proper blade set-up procedures (tension and tracking).
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Understand what results are produced by different blades.
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Use proper techniques when sawing.
Bandsaw Alignment
The blade of a bandsaw ties the upper and lower wheels together, becoming part of the overall machine. Inaccuracies in the shape, balance, and alignment of the wheels are transmitted to the blade and have a major effect on its cutting action. Thus the wheels and tires need to be round and balanced, and both wheels need to be aligned in the same plane. (See Mark Duginske's article "Bandsaw Alignment" in Wood News Issue #20 Fall 1987 pages 6-8.
Proper Blade Setup
Proper blade setup can make the difference in between good and bad results. By taking the time to tension tension and track the blade correctly and set the blade guides properly, you eliminate variables that can produce bad results. Here are some specific techniques.
Tension
Tension can make or break your blade's performance. Most people don't have a gauge to measure PSI (pounds per square inch). Few of us can correctly identify a blade's musical pitch either. (However, if one of these methods works for you, by all means use it.)
To find the correct tension, you can start with the tension scale on your saw, but you will probably need to fine tune the adjustment. With the saw unplugged, increase the tension on the blade until pushing on the side of the blade with your finger using a moderate amount of force deflects the blade about a 1/4" from its normal position. Do this along an unrestrained stretch of blade. (Back the guides out of the way first if only the front stretch of the blade is accessible on your saw.) The exact way that you push is not as important as doing it the same way every time, so the you develop a feel for what is the right tension for a particular blade. You can initially learn the correct tension experimentally by cutting a piece of scrap wood using different blade tensions. A blade that is undertensioned will be extremely sensitive to changes in feed pressure (more on this under Operator Technique) and you will have a tendency to bow in thicker wood. A bow can also be caused by other reasons. Too much to tension for one person may not be for another depending on the machine being used and personal work habits. When too much tension is put on the blade, premature blade breakage and poor tracking can occur, but most important, you can damage your machine by trying to make it reach a blade tension greater than the machine was designed to operate at. Good results come easier when using blades that serve your specific needs, rather than forcing one blade to do all jobs.
Tracking
After tensioning, track the blade to a correct position on your wheel. On a crowned wheel machine (such as Delta, Jet or Sears), this should be in the middle of the wheel no matter what the blade size. On a flat wheeled machine (such as Inca), smaller blades (3/8" and smaller) are tracked in the middle of the wheel, while blades 1/2" and larger should be tracked with the teeth just hanging off the edge of the wheel. Check the tension again to make sure it hasn't changed (new blades can stretch and the tracking process can also change tension). Always remember that tracking while rotating the wheel by hand will take care of major tracking adjustment, but finer tracking adjustment may need to be made with the saw running (with the cover on of course). So when you first turn on the saw, bump the switch on and off, and bring the machine up to speed slowly, allowing you to make small tracking adjustments if necessary.
Blade Guides
Before starting the machine it is necessary to adjust your blade guides properly. The blade guides are of two types, the thrust bearing and the side guides. Most bandsaws feature a thrust bearing and a pair of side guides above and below the table. The upper and lower guides are set the same.
Set the thrust roller bearing right at the back of the blade on the small blades (1/4" and smaller). On bigger blades, leave a gap of about 1/32" between the blade and the bearing to allow feed pressure to be absorbed. At no time should the blade bear hard on the thrust bearing when the blade is idling. If your thrust bearing happens to be adjustable left to right, it should be set so that the blade intersects the bearing about 3/16" from the outer edge of the bearing.
The side guides (which can be either roller bearings or mild steel blocks) are meant to prevent blade twisting and should be set as close as possible without touching or binding on the blade when it is idling. The blade will of course touch these guides when wood is being cut. Be sure to position the side guides behind the teeth, so that the teeth themselves do not pass directly between the guides during a cut.
An interesting experiment is to set the side guys too far from the blade and notice how increased feed pressure and turning make the blade wander.
A good trick for setting the side guides (if they are both horizontal) is to pinch them against the blade and rotate the wheel about a quarter of a turn. As the blade moves through the guides, it will move them apart slightly.
Bandsaw Blades Answers
The Bandsaw Balancing Act Part 2
Learn more about using, setting up and tuning Bandsaws:
Understanding Bandsaw Blades - Everything you need to know!
Are your bandsaw wheels coplanar?
What is the best Resaw technique: 3 Ways To Resaw
Shop:
Bandsaw Blades
New Complete Guide To Band Saws - Mark Duginske's highly recommended book on how to use bandsaws