Hi everybody. I recently purchased a Powermatic 14″ bandsaw and am having some vibration problems. I mostly just read here and rarely post, but today I’m hoping I can pick your brains. I have run the saw with progressively fewer parts in motion–with blade, without blade, without belt. There is a little less vibration with each step but it never goes away. All bolts are tight. The saw cabinet is not bolted to the mobile base, as the base is one where you insert plywood into four corner pieces, and in the corners is where the bolt holes are in the saw cabinet. There is no runout on the motor pulley. The surface of the upper wheel, not tire, has about ten thousandths of runout, and the lower wheel has about six thousandths. The hubs of the wheels appear to travel in eccentric paths as the saw runs. Not sure if that is vibration being reverberated upward through the saw, or if there is something more wrong with the wheels. And the saw cuts straight. The saw takes a serpentine belt, not a v-belt, so I can’t use a link belt. Anybody have any thoughts? Thank you for any help.
Replies
If you've still got vibe w/o the motor belt, then there are two areas to explore:
1) balance of the rotating parts attached to motor shaft
2) Stiffness of the structure mounting the motor.
Is this new or used? With so little runout at the wheels, the eccentric-looking hubs are most likely an optical illusion. As another poster mentioned, make sure the motor is properly bolted down.
How much vibration are we talking about? Enough to knock over a nickel sitting on the table on edge, or enough to shake your work around?
Maybe it's just personal prejudice, but I don't think much of those plywood mobile bases. Does the vibration go away when the saw is on a solid floor? I bet it does.
Pete
Hi Pete. The saw is new. I have suspected as well that the way the hubs of the wheels appear to travel is an optical illusion created by reverberation. The vibration is not enough to move my work around but is enough that the saw would never pass the nickel test. Tonight I'm going to have someone help me pick the saw up off its base and put it on the floor. We'll see what happens then. I have used these bases before without problems, but then with those machines I was able to bolt the cabinets to the plywood. As Dave mentioned above, there could be something out of balance with the motor pulley, and that is something I had overlooked checking. I will take it off the arbor and see if the vibration goes away.
Sounds like a good plan. It may be that the base isn't sturdy enough (likely) and/or that a frequency in the motor is finding a natural frequency of the base and machine.
Less likely but possible is that the sheave attached to the motor is bent or not running true. It sounds like you have a dial indicator, so you check the amount of wobble in the surfaces of the sheave that touch the belt. I would expect a significant amount of wobble to be visible to the naked eye as the motor slows down also.
Pete
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