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Adventures in bandsawing.

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  • Adventures in bandsawing.

    Had a little fun tonite. Was sawing a piece of I beam that's just a tad beyond the capacity of this 4x6. Marked it, clamped it, supported the outboard end cause it's a heavy piece, got the cut going, then left it to do other things while it worked. As expected, the cut got to a certain point where the beam of the saw came down on it and it doesn't go any lower. Fine, shut the machine off, and I'm going to rotate the piece and finish the cut from the other side. Done this about five times now on this same piece, which is only about 4 ft long by now. Anyway, I get about 2/3 of the way through the web before I have to rotate it.

    So now I find that the cut has closed up and I can't get the blade out. Hmm. I make up a wedge from a scrap and try to open up the cut. No chance, the scrap just mashed. Make up another wedge from a section of old bandsaw blade and try to drive that in- no luck there either. It doesn't mash, but it won't stick in the groove- just jumps out.

    So there I am- what to do- I managed to wrestle with the piece, getting it ahead of the fixed jaw and slowly rotating it downwards as I get the cut going in deeper. I'm holding it by hand now since there's no way to clamp it. Finally the web is cut through and I'm into the flange- bang! The blade jumps off the wheels. I can't open the door to put the blade back on because it's down against the beam and I can't get in there. I can't raise the saw because the blade won't rise into the closed-up cut. I don't want to wreck the blade, so I go at it again with the wedges and flat blade screwdriver bits. This time I managed to get the first wedge to go in, then after that I get the blade up and wedge below it, pull some other wedges and get the blade out of the cut. Finally I can raise the saw to put the blade back on and finish the job.

    Now I get to open the door and I find the blade has broken anyway. So, on with an old blade and worry the thing to death until the piece is finally cut off.

    An interesting situation- why did the cut close up this time when it hadn't before? The simple answer is that this beam had been welded at one time to lengthen it, and I was getting closer to the weld with each piece I cut off. This cut was about 3/4 inch from the weld line, and I guess there was so much stress in the material that it warped. My plan all along had been to cut what I needed from this piece, and then toss the section that had the weld in it. I just got too close to the weld and the effects of stress-relief. I definitely will remember this when I next cut from the remains of the beam.
    I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

  • #2
    My customers that cut beams on big machines typically use a wide set blade to avoid the blade being pinched. I beams are known for this problem.

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    • #3
      Sounds like a fun time! I have had a broken blade welded back together before to get some more life out of it.
      Andy

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      • #4
        That is something I did not know. This particular cut closed right up, metal to metal, with the cut about 4 inches in and 2 inches to go. At first I looked at it as if it was a piece of 1/4 inch thick plate 6 inches wide being cut cross-wise. I couldn't imagine how there would be that much stress in a flat sheet- but then the beam is formed in a different way, probably inducing a lot of strain in the web.

        Next time I cut into the remains of this beam, I'm not going to walk away from it. If I see the cut closing up, stop right now. It still might be difficult to extract the blade, but maybe what I could do, or could have done this time, would be to heat the remaining part of the web with a torch. The edge with the flange would remain cooler, and the cut might open up enough to let the blade out.

        Fun time- yeah. I didn't lose my cool, at any rate. I'll have to give the blade a good look over to see what happened. I did quickly check to see if it had been developing cracks, but didn't see any. I didn't think to see if it broke at the weld or not. I will see if it's long enough to allow an angled and feathered silver solder repair. It should have some life in it yet.
        Last edited by darryl; 03-06-2013, 08:51 AM.
        I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

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        • #5
          Some days just go like that!! Lol

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          • #6
            Next time, just insert a wedge when the cut gets deep enough to support it, but not to deep to close up on itself. Just like cutting trees

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            • #7
              Maybe next time mark it out, use a sawsall or a gas axe to rough it to length and then use other methods (angle grinder, etc.) to get it to final size. How exact did the cut have to be?

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              • #8
                Originally posted by Dan Dubeau View Post
                Next time, just insert a wedge when the cut gets deep enough to support it, but not to deep to close up on itself. Just like cutting trees
                I'm not sure how wise this is, but I knew a guy who arc welded a "bridge" over the top of a piece of I beam about when you stuck the wedge in.. This is probably an effective way to weld the blade into the work, ruin the bearings in the saw, and/or screw up any blade heat treatment, or weld the work into the vise, but one time, it worked for him. I never got a straight answer as to why his log splitter needed a perfectly straight saw cut instead of just cutting torch and why cleaning up the bridge didn't matter (probably the remains of the bridge was on the side facing down), and why he had to use that particular distorted piece of beam. After the cut completed in the monster beam, he had to cut out the bridge. Probably was outta O2. I think he did it just to become legend. I suppose there's worse reasons to do something weird.

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                • #9
                  Sounds like you had so much fun. What's your band saw?
                  if you can't take criticism, do the right thing.

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                  • #10
                    Bandsaw is a cheap 4x6, which I have coaxed into being fairly decent. The blade guide system is an abomination of some kind, so I tend to leave the moving guide in a fixed position, and that's where it's adjusted to so it will cut squarely, etc. I think the next model up would be good for me to have now that I've progressed deeper into this hobby, but this machine has done it all so far.

                    I am considering building a second machine which will not have the blade twist system, but still have guides of course. I'd like the wheels to be bigger, but they can be closer together so I could use the same length of blade. The height capacity would be much more limited, but it would have more depth of throat, and I'd use it for cutting sheet materials, cutting off bolts, etc. Most of what I cut is small parts, and there's a lot of thin stuff, so I'd probably have a 14-18 on it, which means I could put a coarser blade on the 4x6 and use that mainly for thicker and larger materials. The new machine would have a larger, sturdy table and the alignment would be right on.

                    Still though, a larger bandsaw would be good to have- maybe down the road a ways though.

                    I like the idea of inserting a wedge to keep a cut open- I'll have to remember that 'trick'.

                    How exact do my cuts need to be? Good question. Much of the time, if the cut is square, the only other finishing to do is a few touches on the belt sander. But if the cut is off, then there's going to be time spent squaring it up. Mostly I'm making fixtures, or small projects, where the accuracy should be pretty good. So, yes, I want it to cut squarely, both ways. It's not often that a cut can be off and still be fine for the project at hand.
                    Last edited by darryl; 03-06-2013, 08:29 PM.
                    I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

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