Problems with JET bandsaw

[jonmulzer]

I had a slightly to slightly serious vibration issue last time I used my new to me bandsaw. I went through all the normal causes this evening starting with a possible bent axle considering the hit this machine took on top with the previous owner. The wheels and tires are within .002"-.004". Next I checked that the wheels were balanced and although my first three spins all landed within 2" of the same spot when it came to rest, the next several were all random. Then I noticed that the upper wheel seemed to be wobbling like a hula dancer. So I rigged up my dial indicator to check that and it shows the upper wheel as having ~.030" wobble to it. That seems excessive. The lower wheel is within a couple of thousandths. So it seems I found my problem unless someone else comes up with anything else or disagrees?

When I pulled the belt off to check the balance on the lower wheel it did not seem to have any memory but I am going to pick up a link belt for it anyway I believe. I will be in Woodcraft next week to pick up a special order so I can get it then if they have a reasonable price. The special order is a 1 micron upper bag for my dust collector to replace the fine dust spreader that is on there now and two boxes of plastic lower bags. Should be quite an upgrade and if anyone has a 1hp Delta dust collector they have the upgraded bags for $20.

Also, Kreg sent me the replacement knob for the fence I added very quickly. It was here within a couple of days so not only did they make it right, they were very speedy about it.

[Tom Slick]

Does it vibrate while running with no band?

[Uncle Cracker]

That upper wheel wobble is too much. You may have a bent axle or something like that. Also, the blade itself can get squirrely if left tensioned for a period of time.

[cgallery]

I know you know this, but the upper wheel has lots of play in the tension mechanism until you get a blade under tension. So you have to have a tensioned blade on before you can test for runout on the upper wheel. You can also hand-spin the wheel and w/o touching it w/ anything, you should be able to easily observe a .030" wobble.

A bent top axle shouldn't cause a wobble, as the axle stays put and the bearings spin on the axle.

Is it possible that you have a bad bearing(s)? Or a bearing that isn't snug in the wheel housing?

[jonmulzer]

I know you know this, but the upper wheel has lots of play in the tension mechanism until you get a blade under tension. So you have to have a tensioned blade on before you can test for runout on the upper wheel. You can also hand-spin the wheel and w/o touching it w/ anything, you should be able to easily observe a .030" wobble.

A bent top axle shouldn't cause a wobble, as the axle stays put and the bearings spin on the axle.

Is it possible that you have a bad bearing(s)? Or a bearing that isn't snug in the wheel housing?

I set my dial indicator up at the bottom of the wheel so it was putting tension on the tracking mechanism itself and I took all my readings with my hand off the wheel. I could put the blade back on it and check again, but I am pretty confident in my methods. The dial indicator always went to .030" positive at the same point on the wheel and always come back to zero at the same spot.

The last time I used it I could see the blade moving about oddly and I thought it was moving about around the radius of the wheel. This I believe explains it.

I don't think the bearings are bad. If I give the upper wheel a good spin there is zero noise and it spins for a few minutes before coming to rest. Do you think that is good enough to answer your question or should I disassemble to check more thoroughly?

[toolguy1000]

what model bandsaw do you have? i'm sorting out an 18" jet jwbs-18. perhaps some of the issues i've overcome are applicable to your situation.

[jonmulzer]

I can't remember the model number right now but it is the 14" closed stand model with 1hp. I have posted about it previously. I would look right now but I am already in bed and responding from my Blackberry.

[Uncle Cracker]

A bent top axle shouldn't cause a wobble, as the axle stays put and the bearings spin on the axle.

Not all by itself, true. But it can displace the bearings and cause the wobble. That's what happened to my first bandsaw... I replaced the bearings once, and thought I'd cured the problem, but the wobble returned soon after. The problem did not go away until I replaced the axle.

[cgallery]

I set my dial indicator up at the bottom of the wheel so it was putting tension on the tracking mechanism itself and I took all my readings with my hand off the wheel. I could put the blade back on it and check again, but I am pretty confident in my methods. The dial indicator always went to .030" positive at the same point on the wheel and always come back to zero at the same spot.

I don't think the bearings are bad. If I give the upper wheel a good spin there is zero noise and it spins for a few minutes before coming to rest. Do you think that is good enough to answer your question or should I disassemble to check more thoroughly?

Sounds like you've you've got it. And from UC's comment below, I guess it could even be the axle.

I suppose you could remove the wheel and with the hub on a flat surface you could check the distance between the rim and the flat surface around the perimeter. That may tell you whether the wheel itself is bad, or if the axle is the culprit.

It wouldn't be a perfect test, because the hub may not be perfectly perpendicular to the axle bore. But if the rim is out .030" in the test I propose, I'd say the wheel is bad. If you get a much different number, then I'd suspect the axle is bad.

[jonmulzer]

I checked it on the bench. It seems to support my findings on the saw. Also, upon removing the wheel I noticed there are probably a dozen holes drilled on the backside. They must have had balance issues with this one at the factory. Should I order replacement bearings also or do they come with them already installed?

[cgallery]

I checked it on the bench. It seems to support my findings on the saw. Also, upon removing the wheel I noticed there are probably a dozen holes drilled on the backside. They must have had balance issues with this one at the factory. Should I order replacement bearings also or do they come with them already installed?

I guess you'll have to ask Jet, though I kinda doubt they'll have bearings installed already.

[jonmulzer]

I guess you'll have to ask Jet, though I kinda doubt they'll have bearings installed already.

Agreed, and at $16.52 for a $1.50 bearing I am not getting them from JET either.

[cgallery]

Agreed, and at $16.52 for a $1.50 bearing I am not getting them from JET either.

Where are you going to find them for $1.50? They're BIG bearings.

[jonmulzer]

I exaggerate some, but they are still way overpriced. I would have to price them, but they are less than $5/per easily.

[jonmulzer]

Well, the bandsaw was put back together this week. New wheel, tires and a few odds and ends. She cuts like a dream! Not a bit of vibration now and would easily pass the nickel test.

Cgallery, I found the bearings for $1.42 a piece locally. They really aren't as expensive as you think and that was for sealed bearings to replace the shielded ones that were in there. I was originally going to reuse the old bearings but that did not work out. I took it to work (we have a full machine shop) and was going to pull them during my lunch break but one of the owner's insisted I have one of the other workers do it so I could keep my mind on real business. Who am I to complain when he puts an entire machine shop at my disposal? But the old bearings got trashed while cutting them free. So I picked up new ones from a local bearing supply. I bought a couple extra in case I ever need to replace the ones on the lower wheel also.

Pretty happy with the saw though. I fed some scrap 5" material into it today and with a 1/2" 3tpi blade it would take it as fast as I could feed it without a bit of complaint.