Tuesday, December 9, 2008

How to Tune a Bandsaw

Bandsaws are great tools to use in any woodworking shop. They make clean, hard cuts and very versatile. However, if you bandsaw is not tuned correctly, it can break blades, wonder off-track, mess up your project, or cause serious bodily harm and injury. Here is how to tune up yoru bandsaw and keep it working perfectly.

UNPLUG YOUR SAW: This is the first and most important step. Unplug your saw first. Open the doors, and install the new blade or access the old blade currently on the saw. Raise up your guide all the way to the top of the mouth as well.

TENSIONING THE BLADE: The first thing to do is to put tension on your bandsaw blade when you install it. This tension is key for holding the blade tight against the wheels. Do not rely on the tension gauge on your bandsaw, as they are always inaccurate. The best way to make sure your blade is tightened correctly is to pluck it like a guitar string and listen for a clear tone. If it makes a dull thud, then you have to tighten it some more.

CHECK THE DEFLECTION OF THE BLADE: Next we need to check the deflection of our blade. The tone alone is not all we us to make sure the blade is as tight as it needs to be. We want to push sideways on the blade right under the guide to test for movement. Raise your guide to the top of the mouth opening, and then push sideways on both sides of the blade. We do not want it to deflect more that 1/4 of an inch. If the blade defects more that 1/4 of an inch, then it needs to be tightened, if it deflects less than 1/4 of an inch, it needs to be loosened.

TRACKING THE BLADE: When your saw is tracking correctly, the blade runs on the middle of the wheels. To adjust the tracking of your bandsaw, you need to tilt the top wheel in relation to the bottom wheel. A knob behind the upper wheel housing controls this adjustment. Make sure your blade is tight then spin the saw by hand and adjust the tracking control until the blade is running in the middle of the wheel. Once it sits in place after a few spins by hand, close your door covers, plug in your saw, and gently step the motor by flipping the power switch off and on so that the wheels gently spin and track the blade. The blade should maintain its position. Repeat this several times before running the saw at full speed. If the saw blade continues to slip off, then you will have to align the plane of the two wheels. Do this by taking a yard strick and a level, and placing it against both wheels. Adjust the top wheel it is level with the bottom wheel. Your level should be flush with your yardstick for accuracy.

SQUARE THE BLADE AND THE TABLE: Loosen the knobs that lock the table in place, and then hold a small square on the table with its blade against the saw blade. Square the table to the blade and lock it in place with the bolt or nut under the table.

SET THE GUIDES: Most bandsaws have two sets of guides - one on top of the tbale, and on below the table, aligned with the blade. The guides can be either a rear guide bearing and two guide blocks, or a rear bearing and also two side bearings. On either version, the rear bearing resists the force that you apply as you push the board past the blade and the guide blocks or bearings on the sides prevent the blade from twisting out of position. To adjust these, we want to move the guide up about halfway between the table and the top of the mouth opening. Set the rear bearings first so that they almost touch the blade. Leave about 1/32” gap between the blade and the bearing. Slide a piece of paper or a dollar bill in between them for accuracy. Then set the guide blocks or the side bearings to the same distance from the blade using the same piece of paper or dollar bill. Lock them down.

DO SOME TEST CUTS: Get a scrap piece of wood, and make a few test cuts in the wood to see how far the blade defects, to see if it is tracking correctly, and to see if it is rubbing up against your guide bearings on the rear or on the sides. If the saw is still cutting off, be sure to readjust the plane of the top and bottom wheel, as this is the most common issue.


Clean your bandsaw blade tires to keep the bandsaw working properly. If you do nto have a brush on your bandsaw to clean your tires already, install an old toothbrush as a brush. Cut the handle short enough to fit in the bandsaw box above the bottom tire, heat and bend the handle below the head of the brush into a 90 degree angle, and then bolt the brush in place.

Round the rear edges of your band saw blades with a medium-grit oils stone by holding the stone flat on the saw table and gently touching it to the back of the blade as the it is running. This makes it easier to cut tight corners and radii.

You will also have to find the new center cut with your bandsaw after you make your adjustments. Draw a straight line down a 2 foot piece of scrap wood, and free-hand cut along that line as closely as you can. When you get halfway into the wood along the straight line, mark a pencil line along the board and onto your table. This is your new center-line. Adjust your fence against this angle for straight and accurate cuts.

Do not put too much tension on the blades. It can cause the bearings to fail prematurely, it can cause the blade to snap under use, and it can cause flat spots on the tires.

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