Band Saw Blade Tracking

I received a set of urethane tires and a couple of band saw blades for Christmas.
I installed the tires and a 3/16" 4 tpi skip tooth blade, centering it on the tires.
As I was adjusting the blocks, I turned the wheel and the blade moved forward on the tires, settling about 1/3 of the way from the front of both tires. I was rather surprised, because I knew I had turned the wheel just a few minutes before and the blade had stayed centered.
Paying close attention to the blade this time, I turned the wheel again and the blade moved back to the center of the tire and stayed there. Now I was really confused.
After screwing around a little more I figured out what was happening:
If I turn the wheels *backwards*, the blade moves forward, settling, as I said, about 1/3 of the way from the front of both tires. As soon as I turn the wheels in the right direction, the blade moves back to the center of the tires and stays there.
Does anyone know why this happens? I checked the alignment of the face of the wheels and they appear to be aligned correctly, so I don't think I'm dealing with a tilted wheel.
I have not turned the saw on yet, since I'm still cleaning it and making adjustments, but I'm curious about why the blade would do that and if I should be concerned.
Thanks!
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DerbyDad03 wrote:

As long as it stays in the same place on the wheel - not necessarily on the center - when the saw is running, you are good to go.
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dadiOH
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Thanks for the response (you too, Jack) but I'm still curious as to what is happening.
When I spin the wheels in the forward direction, the blade stays right in the middle where I put it as I tightened the tensioning knob. However, when I spin them in reverse direction, the blade finds a new home and stays there, unless I spin the wheels in the forward direction again which causes the blade to return to it's original center position and then stay there.
I don't see how that's physically possible.
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As long as it is working it should be OK. I decided a long time age that things that work aren't worth stomach acid.
BUT - My wild, mostly uninformed guess. One edge of the blade is straight and rigid. The other edge is not - it has the cutouts that make up the cutting edge. There might be a very small difference in the tension from the back (smooth) edge of the blade and the front (cutout) edge. Might be enough to cause a little comparative tracking error between forward and backwards motion.
Now that I look at what I just wrote it is probably among the craziest things I have ever come up with. Can anyone do better (crazier)?
RonB
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On Tue, 27 Dec 2011 14:57:45 -0800, RonB wrote:

Even more likely is a burr on one side but not on the other.
--
Intelligence is an experiment that failed - G. B. Shaw

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Count me among those who say if it works OK don't sweat it. But my first thought of the explanation is that when turning in opposite directions, the blade on opposite sides of the wheel will be slacker or tighter depending on that direction, and small differences in alignment from front and back of one wheel compared with the other might account for where the blade ends up running on the tires. My visualation of this is a lot better than my explanation I'm afraid...
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There are no stupid questions, but there are lots of stupid answers.

Larry Wasserman - Baltimore Maryland - lwasserm(a)sdf. lonestar. org
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almost sounds like one or both wheels are canted just a bit.
Can you spin the wheels with enough force to have it run a bit by itself ? - e.g. a slow but running speed ?
Better than just rolling it around with a hand attached.
Martin
On 12/27/2011 3:02 PM, DerbyDad03 wrote:

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wrote:

re: "Can you spin the wheels with enough force to have it run a bit by itself?"
Yes. I just spun the wheel as hard as I could and got multiple revolutions. In the backward direction the blade moves forward as noted above, but when I spin it the forward direction, the blade moves right back to the center of the tires.
As soon as I find the replacement set screw I need, I'm going to close it up and make believe that none of this ever happened. ;-)
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I think I'd start looking at the tires for a possible explanation. Are you tires tight and even? Have you tried recrowning/cleaning the tires with a bit of sandpaper to make sure everything is properly crowned and circular?
Is there any pressure being exerted by the various guides?
Puckdropper
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Make it to fit, don't make it fit.

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On Dec 28, 1:03am, Puckdropper <puckdropper(at)yahoo(dot)com> wrote:

The tires appear to be tight and even. They are brand new urethane tires installed with the tool provided by the vendor.
I'm not sure that I want to take sandpaper to my brand new urethane tires. Is that something that is normally done with urethane tires?
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wrote:

All I ever said was that I was "curious". I'm not trying to fix anything, especially since many of you have already said that if the saw works, leave it alone.
Perhaps you missed the post in which I said:
"As soon as I find the replacement set screw I need, I'm going to close it up and make believe that none of this ever happened."
As far as "hung up", I'm not.
I asked a question and if people are going to be kind enough to respond, I'm going to be polite enough to respond back.
When it was suggested that I sand down my tires, I simply asked if sanding urethane tires was a normal practice. I've never had urethane tires before, so I think I'm justified in asking. I just might learn something.
When someone asked why I was adjusting my guides without the blades running, I simply responded that I don't think I'd want to do that on my saw.
When (if) someone else offers a suggestion as to the cause or asks a question about my saw, I'll probably respond to them too.
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Larry Kraus wrote:

That sounds like a pretty logical reason to me...the teeth moveing in different directions.
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dadiOH
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That makes sense. Thanks.
Still looking for that set screw. :-)
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I'm just curious myself...
Sanding the tires was part of a bandsaw tuneup suggested in a book, and it does help with certain conditions such as vibration. However, new tires probably don't need any adjustments, especially if everything runs fine in the correct direction.
Puckdropper
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On Dec 29, 2:12pm, Puckdropper <puckdropper(at)yahoo(dot)com> wrote:

Did the book differentiate between rubber tires and eurethane tires when they were suggesting that they be sanded?
I'm new to the eurethane tire world, having stumbled across them while looking for information on band-saw blades. Then I found a set of (new) eurethane tires on eBay for my Craftsman band saw which were cheaper than what Sears wants for rubber ones. SWMBO offered to buy them for me for Christmas, so who was I to argue.
Little did I know that a week later Sears would announce the closure of 120 stores. I'm feeling kind of guilty. ;-)
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I don't remember, and unfortunately the book and I are miles apart right now. The one I remember it from was Duginske's Bandsaw Handbook published in the late '80's.
Puckdropper
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On Tue, 27 Dec 2011 09:49:50 -0800 (PST), DerbyDad03

Most likely the new tires are crowned. Narrow blades are tough to track on crowned tires. As long as the blade stays in one spot you're good to go.
--
Jack Novak
Buffalo, NY - USA
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"Nova" wrote in message

Even harder on flat ones.
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On 12/27/2011 11:49 AM, DerbyDad03 wrote:

I can't help on the tracking/centering problem. I am confused as to why you are doing what you are doing. I've always been taught to get the blade guides and back bearing away from the blade and to get the blade running under power on its own. Bring the back bearing to the blade while it is running. I adjust the blade guides forward with the blade running, but they have already been set for the width blade I am running.
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I don't know what kind of band saw and/or guides you have, but I wouldn't want to adjust my guides with the blade running.
Maybe the back bearing, but not the side guide blocks. It's hard enough to get them to hold their position while tightening the cap screws with the saw off, especially the ones below the table.
I always adjust them as close as possible while spinning the wheels by hand, ensuring that I get at least a couple of full revolutions of the blade.
Look at page 13 and 14 of this manual. Would you loosen the cap screws to adjust the guides with the saw running, especially knowing that they are prone to shifting as the cap screws are being tightened?
http://www.managemylife.com/mmh/lis_pdf/OWNM/L0811258.pdf
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