Band saw cutting question


This is a question for those knowledgable about bandsaws. I have a Ryobi 9" bandsaw, BS903 (I think...). I comes with a 1/4" blade. I'm trying to do a straight cut through a piece of weed that is 2" high, and 1.5 inches thick and about 2 feet long. I need to make the cut 3 inches deep. When I do it, I can't get the cut straight, and it appears that the blade wanders a bit back and forth. It's not much, maybe up to 1/8 of an inch, but it's enough to make it very clear that it isn't a straight line. I have the blade guides adjusted fairly tight, about 1/64" on both sides of the blade, and don't think I could adjust them any closer. I'm thinking of getting a wider blade, say a 3/8 6t blade. Any band saw experts care to comment on what I can do to get a straight cut, and if a wider blade will help?
The manual is a bit fuzzy about adjusting blade tension, and I really have no clue how to tension the blade. The manual just says to tighten it until it makes a sound like a guiter string when you pluck it. wtf? Are they serious?
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yup, they are serious. I have a much larger model, but the similarities should help.
Unplug the thing, and open up the covers to expose the blade wheel. There should be a couple (in your case 3, but we are interested in the wheels above and below the table where you cut. The blade wheels ~should~ have a thin rubber "tire" that helps cushion the blade from the wheel. Inspect the blade, the tire, and the wheels to make sure there isn't a bunch of caked up sawdust getting in the way along the blades path.
On my bandsaw, there is a little knob that allows me to tilt the top blade wheel. Tilting the wheel ever so slightly allows the blade to run closer to the exact center of the blade wheel. You know how a pulley would have a concave surface to help align the rope? Well a bandsaw wheel has a convex surface (don't ask me why) and getting the blade to track on the "crown" of that convex surface usually requires a little fine tuning of the blade wheel tilt.
There are all kinds of gizmos you can by to try to make your cut run true, but if the blade doesn't ride on the "crown", then the other things you can do won't ever allow you to dial in your saw completely.
Use a gloved hand to spin the blade as you check your adjustments. The blade tension doesn't have to be "guitar sting tight" at this point... but snug is nice. Once you get your blade to ride on the crown, then close the cover back up and tension the snot out of it. Be careful, as you can accidentally overdo it. A small blade like you mention is fine for cutting curves, but not quite ideal for straight cuts. Don't get me wrong... it can be done. The size of the blade you use will mostly be determined by the ooomph of the motor. Based on your description you may not be able to go a whole lot bigger.
Next inspect the blade for kinks and other problems. If someone used a wood blade on metal, well then you are probably going to want to go get a couple of sharp blades to have on hand.
Next make sure your table is perpendicular to the blade. Sounds silly, but bandsaws (and other tools) lose their settings between uses. Get a plastic triangle if necessary. Move the blade guards out of the way.
Lastly, move your blade guards as close as possible to the work you are doing.. and if you have friction blocks or roller bearings to keep the blade from wiggling around, make sure you use them as well. If you have friction blocks, there should only be a paper-thickness between the friction block and the blade. Pull a dollar out of your wallet as a thickness tester and find that allen wrench and make the adjustment. If you are fortunate enough to have roller bearings, make sure they are set to ride on the flat portion of the blade, and NOT hit the teeth as the teeth go by. Again, just a paper thickness of clearance is what your are shooting for. With roller bearings there ~should~ be a third bearing that rides on the backside of the blade (the thin side OPPOSITE of the teeth) and this will prevent the blade from deflecting back away from your cut.
Go ahead and plug 'er back in and give it a test. LET THE TOOL DO THE WORK! So many folks get hasty and things don't go as well as they could.
Bandsaws will follow the grain... so if your cut is perpendicular to grain, you should get good results, if the grain is ~kind~ of going in the same direction as your cut... the blade will tend to wander. Going extra slow during grain transitions will help.
I have read lots of articles on tuning band saws... and some folks say that a band saw has a pre-determined "wander" that you can compensate for by making a test cut, and then setting up a fence at a small angle to purposefully try to correct the wander. I have tried this, but until I started tuning from the "ground up" as I have lined out here, my results were mixed at best.
Best of luck.
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-snip-

I'll 3rd the 'Yes' - and add that sharpness is also a biggie when you're pushing the limits.

-snip what sounds like good basics-
-snip-

This guy is moving too fast for my taste- but it is pretty cool, anyway. don't look at the video description- just see if you can guess what he's carving before you see it-
http://www.youtube.com/watch?v=YXW55S4X9zo

-snip-

I'd definitely do all the steps listed- and probably on a new, wider, blade. Buy the widest you can find- and only use it for re-sawing, or thick, straight, cuts. [used to be you'd go for fewer teeth on that re-saw blade, too, but I haven't looked at blades in 20 years, so they are likely to have something new out there.]
Jim
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Yes, they are serious. That is how a lot of people tune the saw. Setting up a bandsaw properly takes a little time the first go around. The wheels must be co-planer, the blade must be tensioned, the guides have to be jut right. The biggest problem you have is the small saw. They are difficult to get set straight. and I'm told by others, impossible for accurate cuts. That is the difference between the $99 tool and the $699 tool.
There is a book, The Bandsaw Handbook by Mark Duginske (or like that) that is very good explaining the setup and use of the bandsaw. Worth reading even though it cost about 1/4 the cost of your saw. .
Oh, the 3/8" blade can be harder to tension. The wider the blade, the more pressure needed.
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Tip: Get a pitch pipe. Tune the 1/4 blade to a 440 A, 3/8 blade to 256 C. Could also use a piano or electronic organ.... Or, a guitar!
:)
With the blade positioned under moderate tension, I turn it on, get the blade to seat, and finish tensioning it while it's turning. I "sink the blade down" much as you sink a nut down on a bolt, without stripping anything -- you sort of feel the maximum tightness.
--
EA

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Zootal wrote:

Use a table saw.
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WHERE DO YOU GET WEED THAT BIG? HOW MUCH DO YOU PAY? CAN YOU SCORE A COUPLE OF STICKS FOR ME?
Steve ;-)
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Man, you took the words right out of my pipe....
--
EA

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> Steve ;-)
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IIRC,there are blade tension gauges you can buy,but,yes,the tension should be very high.

would that be for medicinal purposes??

For the OP;
to keep a bandsaw blade from twisting,you need to keep the blade guide as low as possible,just enough to clear the workpiece. (and see what you're doing...) you also cannot push too hard,forcing the work.
shouldn't the blade guide blocks RUB slightly on the blade?
A wider blade WILL help. wider blades are used for rip cuts like you appear to be making. sometimes called resaw blades,used to make thinner boards.
--
Jim Yanik
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From what I've seen you your posts, Steve, you are doing just fine as it. You really don't need anything stronger as you seem to already be in orbit :-)
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Thanks to all those that responded with advice and suggestions. I went and picked up a 3/8 6t blade, installed it, cinched up the blade guides, and now I'm making perfect straight cuts. Veeerryyy nice, just going to a wider blade made a *huge* difference.
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On Thu, 17 Dec 2009 00:13:48 -0800, "Zootal"

A wider blade and a bandsaw tuneup will certainly help. It is typical there is a "drift" angle when cutting a straight line with a band saw and you correct for that by adjusting the piece. Take your time cutting.
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wrote:

I put a wide blade on it, and played with it a bit. Going to the wider blade made all the difference in the world. I think I pretty much have it tuned the way I want it. It's not the highest quality saw out there (it is a Ryobi, after all), but I can get it to do the job. Bandsaws are a bit touchy, aren't they? :-)
What I wasn't sure about was how to tension - how tight is too tight, or too loose. There is a very wide range of tension that results in a nice guitar-like twang. It would help if the manual suggested actual pitches to shoot for, instead of just saying it sounds like a guiter. Just going from the low E string to the high E string is two octaves, let alone working your way up the neck on the high E string, which is another octave and a half or so.
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-snip-

Here's a tool that will do it for you- http://www.grainger.com/Grainger/items/2CDN9
I imagine there is a cheaper one out there- but $419 gets you a real fine piece of equipment.<g>
Problem with this kind of thing is that the guy who could make that tool pay for itself can probably set by feel just fine. It is us guys who only use the bandsaw every couple years that could benefit from having a tool telling us what 'tight' is.
Play around- and if you're sawing on and off for a week or two you'll probably get a feel for what your saw, your sawing speed, and your blade like best.
Jim
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On Sat, 19 Dec 2009 17:13:14 -0800, "Zootal"

Just tighten it enough such that the blade makes a tune when plucked. If there is no sound, it is too loose.
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