The short of it is this: I have a Jet 8″ jointer. It produces such vibration, as to make it almost unusable. I thought it might be because it sat unused for an extended period of time and the belts had taken on a permanent shape, so I replaced the belts. Same thing. I checked the motor pulley, and found it about 3 1/2 thousandths out of round. That doesn’t seem to be a lot for such an application. The knife pulley was even less out. I then took it off it’s Jet rolling stand, and sat it on the floor. Not much improvement. I watched the belts while it ran, and the motor, though mounted quite securely, seems to want to move up and down as it runs. I removed one of the belts, and seemed to get some degree of improvement. I am at the end of my rope, and ready to kick away the chair!!!
The solution is in your hands now boys and girls, as I am fresh out of clues and ideas. I will patiently await your expertise. Thanks for any help you might provide.
Frustrated
Edited 11/13/2004 9:21 am ET by TOMBROWN10
Replies
Have you tried removing the blades and seeing if the vibration continues? Out of balance blades could cause this.
Try reducing the system to the simplest parts, and adding parts from there. Try the motor disconnected from all belts, then add parts one by one.
Good luck
Paul
I second Pauls recommendation. Reduce it to simple logical steps. Also make sure the gibs holding the knives are of the same weight. If it's new contact Jet for warranty service or tech help if it's out of warranty. Did it act like this when you first got it? If in Western Mass I do house calls for machine repairs!
Edited 11/13/2004 10:36 am ET by rick3ddd
Remove belt and run.If you still get vibration it's in the motor shaft.If not ,the cutterhead bearings may need to be replaced.Are all the knives in?if you recently changed them and one is missing the cutterhead will be out of balance.I saw this once when the cutterhead had four knives and only three were replaced.Not sure why removing one belt would help, could you have too much tension on the belts. Over tension will cause bearing failure,I believe,not absolutely sure though.
mike
Edited 11/14/2004 11:38 am ET by MIKEK4244
This is my best guess given limited information: one of the pulleys has been hit and damaged, narrowing the "v" groove at one point causing the belt to ride up and then drop back down into the groove as the narrowed part of the pulley's rim comes around with each revolution.
There are other possibilities, a missing knife is a possible cause of vibration, but that wouldn't cause the motor to be moving up and down.
This shouldn't be hard to diagnose. Unplug the machine and rotate the drive line by hand, you should be able to feel resistance at a certain point while turning, and see something shifting as you rotate the parts. If the machine rotates smoothly when turned by hand, but vibrates when powered up then the problem is in the motor or the cutter head, but what you are describing sounds like a pulley, belt, or bent shaft problem.
I suspect there is something in the machine's history since it last saw regular use, has it been banged around a bit as it was moved perhaps? - that would give a clue as to the problem. I would be interested to know what you find.
John W.
Edited 11/14/2004 6:59 pm ET by JohnW
It's your cutterhead bearing. The same thing happened to a guys powermatic I was working with. The thing vibrated so bad I told him I wouldn't use it until he got it overhauled. When he did, that is what the tool shop fixed. When you rotated it by hand you couldn't tell it was loose or worn, but that's what it ended up being when they took it apart. Unfortunately, it cost him a couple hundred bucks to fix, but it will be worth it.
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