metal bandsaw won't cut straight

Hi guys.
Got a 4"X6" Tiwanese bandsaw. It cut fine when I got it a couple of years
ago, but I must have messed something up. It now will not cut straight. It
cuts almost a 30 degree angle, drifting fromthe top of the cut towards the
bed as it cuts. As a result, it also is less straight along the bade as
well. It often seizes the blade and stalls. Quite often the blade breaks.
I have adjusted nearly everything I can adjust (maybe that's the problem).
The only thing I can think of left is perhaps the blade isn't tight enough.
It takes a 64 1/2 inch X 1/2 inch blade and there is barely enough thread on
the tensioner to put the blade on loose. I tighten the tensioner by feel
until it "feels" tight, but I don't really know how tight is should be.
Any advice would be appreciated.
thanks
Reply to
Kelly Jones
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Have you tried a new blade? Most probably the teeth on one side have been dulled, so only one side is cutting. The other side is just dragging. There is NO adjustment that will correct for an unevenly worn saw blade.
I am sure by now you have aligned all the guide wheels. However, these saws have a tendency to slip off the bearing/wheel that rides on the back of the blade. I have two saws. One had to have one bearing/wheel removed and a shim washer added to keep the saw centered on the bearing. It was so sloppy the bearing would slide to one side and let the blade ride on the pin holding the bearing. This also made the saw cut at an angle. The other saw doesn't have the problem.
As far as tightness, my saws are pretty tight. I can't put a number on it, but have to work hard to get it any tighter. Also, the saw will blade will expand with the heat as it cuts, so really tight cold is not so tight warm or hot.
Hope this is of some help.
Paul
Reply to
co_farmer
Mine won't cut straight unless it's on a flat floor, because otherwise the frame twists. The quick check is to stand a square up in the vise and raise the blade next to it. If it follows the edge of the square it will cut straight.
You could clamp a light aluminum bar to the blade above the teeth and see if the bar is perpendicular to the bed, or if it twists near either guide.
jsw
Reply to
Jim Wilkins
The problem should be fairly easy to resolve, depending upon what the primary fault is.
You can proceed by starting with a square as Jim suggested, and also closely inspect the parts that are related to the blade cutting path. The guide bearings may need adjustment or replacement. The guide bearing blocks may need adjustment. The pivot shaft for the upper saw casting shouldn't have a lot of slop, as the locating holes may be worn excessively. Eliminate most of the axial movement with washers, spacers or shaft collars. Blade tension is about right when you tighten the tension knob as tightly as you can by hand. Many 4x6 bandsaw users report that a quality, big brand name blade (Lenox, Starrett)will cut straighter than the generic hardware department imported blades.
There are many online user webpages about these saws on the big w3, which can generally be found by searching: 4x6 bandsaw, 4x6 band saw, or similar search terms.
Reply to
Wild_Bill
Insufficient tension can allow a cut to drift. It sounds like yours is not tight enough. "Feels right" is almost always too loose. Here's how I tighten mine: I put a leather glove on one hand, so I can grip the knob more tightly. I put that hand on the adjusting knob & the other hand on top of the first one. Then I turn as hard as I can! Really.
Your problem may not be a matter of tightness, but it could be & it's the easiest thing to check/fix. Try it first & let us know.
Bob
Reply to
Bob Engelhardt
First, check and make sure it is in forward, and not reverse. Since you've changed all the settings, it may be a good thing to start unsetting them, make a cut, and see how that changes things.
They work fine when everything is adjusted right, and you have the switch in the FORWARD position. Or at least on mine, that is.
Steve
Reply to
SteveB
There are a number of repairs out there for the weird ways these machines wear out. Mine regained a lot of its former accuracy when I changed out all the blade guide bearings and the drive wheel shaft bearings (thankfully I caught it before the worm gear stripped from running out of position). I have also had to rebuild pretty much every part of the top wheel support and tension bracket. I am an infrequent user, so mine may have had about the same use as yours has had if you were using yours heavily for those couple of years.
Another place that wears out is in the main hinge where the saw tilts. Have you tried measuring how much the saw falls out of line with a square as you pivot it down while not running? Have you tried wiggling the tilting section relative to the base to see how much play there is, throughout the range of motion? There have been a couple of fixes posted for this, from boring out the hinge portions in both the base and bracket and bushing with bronze bushings, to simply cutting them off and replacing them with appropriately sized pillow blocks when they're too far gone for even that. I've not repaired mine in this way, yet, though I have no doubt that there is some wear there for me to address.
Here's a couple of pages I have found helpful:
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a search on "4x6 bandsaw" will no doubt bring up more.
--Glenn Lyford
Reply to
Glenn Lyford
They take as much tension as you can crank in. The frame flexes before you get into really high tension conditions. If you owned a blade tension meter, it would show you that as hard as you can crank barely is enough for what the blade is rated in tension.
Also, make sure you take the tension off after you're done. I haven't had a frame take a set yet, but it's not good to sit there for days or weeks with the tension left on.
The posters have given you some good suggestions, the cutting wax one in particular. Lennox blades are what I've run on mine, the no-name hardware store and HF blades are just toothed banding iron by comparison. The difference is amazing. You also need a number of different TPI blades, depending on the thickness of what you're cutting, one blade TPI just doesn't do it. Too coarse will result in teeth shucking when cutting tubing, too fine will result in loading up and dulling when cutting thick stock. And they will always dull on one side, change them at that point if you want to keep cutting square (and the blades survive that long).
Stan
Reply to
stans4
All:
Thanks for all the advice. I ordered some Starett blades on Sunday and I'll let you know how it turns out when they get here.
They take as much tension as you can crank in. The frame flexes before you get into really high tension conditions. If you owned a blade tension meter, it would show you that as hard as you can crank barely is enough for what the blade is rated in tension.
Also, make sure you take the tension off after you're done. I haven't had a frame take a set yet, but it's not good to sit there for days or weeks with the tension left on.
The posters have given you some good suggestions, the cutting wax one in particular. Lennox blades are what I've run on mine, the no-name hardware store and HF blades are just toothed banding iron by comparison. The difference is amazing. You also need a number of different TPI blades, depending on the thickness of what you're cutting, one blade TPI just doesn't do it. Too coarse will result in teeth shucking when cutting tubing, too fine will result in loading up and dulling when cutting thick stock. And they will always dull on one side, change them at that point if you want to keep cutting square (and the blades survive that long).
Stan
Reply to
Kelly Jones
Aside from whatever you may have mis-adjusted in your experiments, the main thing is the blade tightness. You should tighten it by hand until the pain in your hand keeps you from cranking amy more. That will get you to the slack side of tight enough. As far as I know, there is no better way to do it.
Also -- beware that if the guide rollers are misadjusted so they press on the sides of the teeth instead of just on the flat surface of the blade, they can crush in the set of the teeth on that side, causing the blade to cut better on the other side, and thus walk towards that side.
I don't know which flavor of the 4x6 you wound up with. The one I got perhaps ten years ago from MSC has nice solid forgings onto which the rollers are mounted. Some others, however, are bent up steel which tends to un-bend a little under stress over time.
Good Luck, DoN.
Reply to
DoN. Nichols
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To be honest -- I've *never* seen a 4x6" bandsaw with a REVERSE switch position. (Nor any larger one which I have used, either.) It is expected that you will put the blade on with the teeth pointing in the right direction.
Enjoy, DoN.
Reply to
DoN. Nichols
564 > =A0 =A0 =A0 =A0 (too) near Washington D.C. |
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> =A0 =A0 =A0 =A0 =A0 =A0--- Black Holes are where God is dividing by zero =
Reply to
wfhabicher
The manual for the Wilton version with hydraulic feed control says to tighten it only enough that the blade doesn't slip.
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I don't now how well that works, the beat-up, kinked blade broke or jammed and popped off the wheels half way through the cut. Great help when I'm showing someone how to use it!
jsw
Reply to
Jim Wilkins
Hmm ... a bit larger -- 5x8" instead of 4x6" -- aside from the hydraulics.
That might suggest that they have it wrong, and the several who have posted here (including me) have it right. I know that I tighten it as much as I possibly can before using it -- and if I don't, it is more likely to pop off the wheels.
Enjoy, DoN.
Reply to
DoN. Nichols
Putting the blade on upside down and running the machine at its highest speed was one of the ways to friction saw material too hard to cut in the normal fashion.
Cheers,
Bruce in Bangkok (bruceinbangkokatgmaildotcom)
Reply to
Bruce in Bangkok
He's talking about a vertical bandsaw, not horizontal, so that "upside down" leaves the teeth in the same place but running backwards.
Reply to
James Waldby
Not really. The machines that will support this type of sawing will have friction-less bearings for both the side and back guides.
We used to do it with a big Doall and I suspect that most of the smaller "hobby" saws won't run fast enough to friction saw well. The Doall operator's manual had instructions for friction sawing and as I remember it Doall sold special friction sawing blades.
It was great for cutting hard materials, I've cut HSS tool bits with it. When the cut is started the feed pressure is very high - you are pushing a piece of metal into a blade running backward - but as soon as the cut starts the feed pressure drops dramatically.
Cheers,
Bruce in Bangkok (bruceinbangkokatgmaildotcom)
Reply to
Bruce in Bangkok
just fixed this agony myself. the frames are cast iron so there should never be noticeable twist. the pivot or hinge is quite robust so this isnt the cause.
take the blade off and wipe it clean of all swarf. clean any swarf out of the 4 guide rollers. clean any swarf off the two end wheels. reassemble it all clean.
now tighten the end wheels to get the blade tight. then go over the 4 guide rollers and tweak the eccentric cam action on them so that they are tight against the blade, and the rollers have the blade tracking the direction of cut perpendicular to the job. when these are correctly tweaked and the blade is tensioned it should cut true.
I now cut dry so that the swarf doesnt stick to the blade and push the guide rollers apart.
It took me two days to work out why it wouldnt cut straight. it does now. Stealth pilot
Reply to
Stealth Pilot
magnetic swarf ? not sticky ? or did you have the coolant too viscous ?
I run with a water based coolant and don't have trouble.
Might been blade tightness or load on a wheel...
Martin
Stealth Pilot wrote:
Reply to
Martin H. Eastburn

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