Bandsaw blade fluttering on 20" saw

[Matt Day]

I'm finally getting to put some time on my new to me Powermatic 2013, but after resawing some small stock the saw began to vibrate/shake and the blade moved forward and backward.
I tried increasing the tension and that seemed to make the problem more violent.
I think the upper wheel is out of alignment and not coplaner to the lower wheel. But since the wheels are recessed inside the frame, I can't put a straightedge across the wheels like on my 14" delta.
Are there any tips for doing this on larger saws? I thought if making some spacers to attach to the wheels but don't want to go through all that if there's a better way.

[Erik Loza]

Bad weld on the blade would be the usual suspect.

Have a different blade you can try?

Erik Loza
Minimax USA

[Matt Day]

I'll give it a shot. Thanks Erik.

[Richard Coers]

Watch it running with the doors open. Make sure one of the tires is not slipping or bunching up on the wheel just in front of the blade contact points.

[Jim Matthews]

+1 on the weld as the usual suspect.

You might also find the blade is longer than advertised.
If you're at the extreme of adjustment, you may not be operating under sufficient tension.

How wide is the blade?
Bigger blades are stiffer, and more resistant to being put under tension.

I've got a similar problem, and it is less pronounced with a 3/4" blade than a beefier 1" blade.

[Matt Day]

The blade is a 1/2" and I've used it for a little while without issue. I've got plenty of more adjustment. I'll play with a new blade tonight and look at the weld of the existing blade, which is a kerf master I think.

[Matt Day]

As I was changing the blade to a fresh one I decided to wiggle the wheel back and forth to see if there was any play, and in fact there was. I took the wheel off and wiggled the arbor and it was loose. I took apart the tension assembly to get the arbor off and see what was going on and there is a lot of play between the arbor and the (2) 6205 bearings. The bearings seem to spin fine and I didn't notice any noise when the saw was on. The arbor basically falls into the bearing instead of being any kind of press fit.

I happened to have a couple 6205 bearings (1 new and 1 used in good condition) from a planer rebuild, and it is clear that it would take some effort to get the arbor into those bearings. The loose bearings are the only bearings on the machine that I did not replace when I overhauled the saw (figures!).

Question is, any reason not to use the bearings I have on hand (6205ZZ) to get it up and running and replace the NTN 6205LU's?

[Rollie Kelly]

6205's are cheap and you only need one new one ,why risk the used one?
Rollie

[Yonak Hawkins]

I think the upper wheel is out of alignment and not coplaner to the lower wheel.

If the blade is tracking correctly it's almost certainly not a wheel alignment problem.

[Duane Meadows]

The arbor basically falls into the bearing instead of being any kind of press fit.

Matt, does the arbor "fall into" the new bearing as well? If so I'd change the arbor as well!

[John Lanciani]

Matt, does the arbor "fall into" the new bearing as well? If so I'd change the arbor as well!

I agree. Hard to tell for sure from the pic but it sure looks like the bearings spun on the shaft.

[Matt Day]

Nope, as I said the arbor is a tight pressfit into the new bearings. I just want to Fastenal and got a couple 6205's that I will put in tonight.

[Erik Loza]

Matt, it is good that you are replacing the bearings but I still think that blade was the issue.

Regarding the arbor shaft, I would hit that with a wire wheel before trying to fit the new bearings on. Possibly you did this already.

Best,

Erik Loza
Minimax USA

[Matt Day]

Well the new bearings made the upper wheel spin forever without the blade on it - definite large improvement. And the arbor really needed to be pressed into the bearings so it's a very solid connection.
All I had time to do was get the blade tracking in the center of the wheel and get the saw spinning up to 60hz a couple times and I didn't experience any of that vibration I had before, and I used the same blade. There is a slight forward/back of the blade but it's minimal, like a couple mm's.
I'm looking forward to testing it out tomorrow hopefully.
Thanks!

[Tai Fu]

Are you sure the play doesn't come from the tracking mechanism? There's a bit of a gap between the pivot points to allow the wheel to tilt, and I have the same problem on my bandsaw too if thin blades are used. The play should disappear when tension is applied... I know it's not bad weld because it does it on every blade.

Sometimes you may also need to adjust the tilt on your lower wheel. I think side to side misalignment can cause the blade to move back and forth... this is not really documented by most bandsaw manufacturer but if your blade sits too close to the edge on the lower wheel despite your tracking adjustment on your upper wheel, you need to adjust the tilt of your lower wheel. If it moves back and forth then you need to adjust the side to side alignment of the lower wheel.