Troubleshooting Bandsaw Vibration

Troubleshooting Bandsaw Vibration

by Robert Feeser

This article first appeared in a thread on theWoodNet woodworking forum. It was compiled and reproduced here for easier public consumption. All Text are the property of Robert Feeser.

Troubleshoot it to find out where the problem is.

Remove the belt. Turn it on. If it still vibrates you know it is the motor and/or the way it's mounted. If the vibration goes away you have eliminated the motor and pretty much the mounting as well.
Put the belt on and remove the blade. If the vibration starts it has to be from one of the moving parts that weren't moving in step 1. That includes the belt, the alignment of the pulleys (most important and the first thing to check), the lower wheel bearings and balance. If it still doesn't vibrate you have eliminated all those things.
Mount a blade and tension it. Move the guides and thrust bearings well away from the blade so they can't touch it. If the vibration starts you need to look at the new moving parts of the system. The problem can be the blade itself (twisted, crooked weld,...) tires out of round (they can have lumps just because they were stretched around the wheels without equalizing the tension all the way around), bad upper wheel bearing or balance, or misaligned wheels. The last can actually cause vibration in some cases, but it's unlikely.

You can judge bearings to a reasonable extent by removing the belt and blade and turning the shafts while paying attention. You shouldn't feel any roughness or hear any noises. Pull the shafts in and out, then up and down pretty hard; you shouldn't feel any looseness.

Wheel balance can be tested by removing belt and blade, spinning the wheel, letting it glide to a stop, and putting a mark on the bottom of the rim. Do it half a dozen times. If the marks gravitate toward the same part of the rim the wheel is out of balance. If they are distributed evenly or randomly all around the rim the balance is OK. Keep spinning and marking until you feel pretty good about whether it's balanced or not.

The concentricity and roundness of the tires can be determined by clamping a block close to the wheel, with a wide blade mounted. Use a dial indicator or feeler gauges to determine the maximum and minimum distance from the side of the blade to the block. Measure to the side of the blade, not to the tire itself. If they are within about 0.01" they are OK. If you don't have a dial indicator or feeler gauges, use your eyes. You can easily see a 1/100" eccentricity in the tire, you just can't measure it.

You can tell whether the blade is OK by examining every inch of it carefully, or by changing blades.

You can tell whether the belt is the problem by inspecting every inch of it. You will usually see that it has taken a set so that there are two sharp curves in it, but that's normal. Just because of that you don't know whether it's bad enough to be causing the vibration or not. If changing the belt stops the vibration, the belt was bad. If running the machine with the old belt on for an hour or so gets rid of the vibration you may be OK, or not. If the vibration is still gone the next time you use the saw, the belt's OK. If you have to run the saw for an hour every time you want to use it, consider replacing the blade instead.

You can check the alignment of the wheels and of the pulleys by holding a straight edge across them. If they are correctly aligned in that plane you can lay the straightedge on them so it touches both rims at two places. If you can do that, though, the shafts may still not be parallel. If you can find a position where you can sight across both shafts (pulleys) or rims (wheels) you can tell whether they are parallel. You need to do that in two perpendicular planes, like horizontally and vertically. But the straightedge verified it in one plane, and you just have to sight across the shafts or rims in the other plane.

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