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Has anyone tamed the infamous HF band saw blade welder?

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  • Has anyone tamed the infamous HF band saw blade welder?

    Just spent an afternoon struggling with my HF band saw blade welder. After more than a dozen attempts, I gave up in disgust. I am welding 1/2" x .020" Starrett bimetal bulk stock. To prepare the blade ends, I used the "flip one end and cut both ends together" method. I did this using a belt sander, a tool grinder, and a throatlesss shear. Got the best results with the shear. To the naked eye, the blade ends appear to join perfectly -- no light coming through. I set the spring tension on the welder clamps to 1/2". In all but two cases, pressing the "weld" button resulted in a shower of sparks and holes blown into the blade edges. In a couple of cases, there were no sparks, just a humming noise, and the resulting joint looked semi-OK -- there was squeeze-out all along the lower side of the joint where the metal was upset, but on top there was only partial squeeze-out, and where there was no squeeze-out, the joint was still visible, indicating incomplete penetration. After annealing and grinding, these joints lasted about 5 minutes of very careful, light cutting before they broke.

    I have a theory about why this is happening. If, despite appearances, the blade ends are not in fact making continuous contact along the full 1/2" width, the welding current will be concentrated at the points that are making contact. That results in too much current at those points, which blows the metal away instead of just heating it to welding temperature. But I don't see how I can prepare the blade ends any better than I am already! I have no idea why, in the few cases where the joint fuses instead of exploding, I get incomplete penetration. Using different spring tensions on the moving jaw doesn't seem to make any difference, and there are no other adjustments available.

    Before I give this up as a bad job, does anyone have any suggestions?

  • #2
    Do you think that a "skarf joint" where both sides of the joint are overlapped and ground to 1/2 thickness would help? Google has lots of examples.

    There was a thread about brazing bandsaw blades the other day, and brazing requires an overlap.

    Dan
    At the end of the project, there is a profound difference between spare parts and extra parts.

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    • #3
      I have one and it works great. I actually used it yesterday for the first time in five years.

      A few questions. There are two buttons, weld and aneal. You are using the weld button for the weld process??
      On mine you set up the spring tension and press the weld button and the weld happens, the blade moves closer together due to preset spring tension, and the machine stops welding BY IT SELF. So there must be some kind of contact inside that is triggered by the spring tension adjustment to stop the weld. Perhaps that is sticking?
      When I weld mine I just CUT the blade with tin snips. Yesterday I was cutting a large block of aluminum and never got back to put oil on it and it bound up and caused the blade to break. Yesterday I did NOT even CUT the blade. I just wiped it off good and welded the break. It worked fine.
      My second question is what kind of cutting oil are you using? If silicone then that could contaminate the weld. I don't know what else would contaminate a blade weld but I'm sure a lot of lubes could. FWIW I use Wal-Mart's brand of wd-40. It seems to work just like wd-40 but doesn't smell and its cheaper.

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      • #4
        Danlb. A scarf joint will not work with a blade welder because the welder holds both sides of the blade and the arc starts and the to clamps move together . This fills the gap imperfections and makes alittle bump where it welded. This now requires grinding so the blade will pass between the rollers on the saw. The blade welder has a little block screwed to the front of the machine that has a slot cut in it. This is a test block to make sure that the blade is not thicker where the weld is. If it was it would bind up when in the saw when going through the rollers and snap.

        If brazing a blade a scarf joint would give a strong connection because of more surface area.

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        • #5
          After reading the ops post again it sounds like the spring tension MOVEMENT is sticking.

          Again make sure that you are using the weld button. The aneal button will do the same but it won't turn off automatically.

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          • #6
            Some welders use a timer, some may have a limit switch. Does that one have a control to adjust for blade size? That will actually control the setting for amperage. If I were troubleshooting, I'd probably take it all apart, check all electrical connections, look for stuck switches or sliding surfaces, i.e. anything out of normal which could interfere.

            When the blade halves make initial contact, the surfaces should begin to melt and to allow the rest of the blade to make contact immediately, so the current spreads over the whole surface. If the current is adjusted properly, only a small area should melt and only a small ridge formed by sideward extrusion. Movement should be rapid enough that no oxidation gets trapped in the joint and no localized overheating happens.
            Besides adjusting the pressure, can the movement distance be adjusted? Are you setting the spacing correctly, does it have strong clamping pressure (good contact, no slipping)? Have you tried changing the spacing, just for testing purposes to see if something different from recommendation is actually better?

            Do you have an old, worn blade you can practice with? Even just an old hacksaw blade will work, or perhaps some steel banding, if not too wide or too thin.
            Polishing the surface of the blades near the cut might help get more uniform current flow.

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            • #7
              Apparently HF no longer sells a saw welder. There is an excellent operating manual on the DoAll Sawing Products web site.
              Search for the DBW-1A welder manual.
              alsinaj, your blade width may be set too high resulting in excess upset. This will usually result in a blown out weld.
              I have the DoAll DBW-1A. Used it yesterday. Nice machine.

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              • #8
                I've always just used my MIG welder. Haven't tried it with the TIG yet. The MIG was always there and set up with small wire I used for sheet metal work. Never had one break.

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                • #9
                  Bimetal blades do not weld with a resistance blade welder. At least not on my old DoAll welder. 1/4" carbon blades no problem, but my bimetals are 3/4". Had better luck scrafing the blade and silver soldering. Made an alignment fixture for them. On my Peerless power hacksaw I use 12" lengths of the bimetal. Now I don't have to buy expensive power hack saw blades.

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                  • #10
                    Exactly. Don't try to weld bimetal blades.

                    If you do try, turn that sucker down until you don't see any more blowouts.

                    metalmagpie

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                    • #11
                      My Grob industrial welder specifically states that is it not to be used for bimetal blades.

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                      • #12
                        Don't weld bimetal? All my bimetal blades are put together with one of those resistance blade welders. Have been for many many years.
                        Andy

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                        • #13
                          I had one of those HF machines and never could get it to work.
                          I took it back and got a refund.
                          I just buy pre-assembled blades -- less frustration!
                          Bill
                          I cut it off twice and it's still too short!

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                          • #14
                            I weld 1/2 inch bimetal with the hf welder and it works fine. The annealing process will determine if it breaks or not. Heat to a dull red and the keep bumping the button with shorter and shorter bumps until the blade temp is back down. The goal is a very slow cool from dull red. Thus removing as much hardness away from the weld as possible

                            Directions are printed right on the machine

                            The blade also must be a loop. You can't weld two short pieces together to test try.
                            Last edited by ahidley; 05-21-2018, 10:17 AM.

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                            • #15
                              Thanks for all the good tips. I'm getting slightly better at using this welder. Using less spring pressure seems to help. Stoning the blade ends seems to help. I also tried using the annealing button, with spring pressure, before welding. When I do this, I can clearly see where there is contact between the blade ends because those areas get orange, whereas the areas with no contact stay black. By pulsing the anneal button just right, the spring pressure deforms the blade ends enough so there is full-width contact. Then when I weld, there are no sparks and I get a good weld. If you lean on the anneal button a hair too much, though, the ends blow out. I annealed after welding and again after grinding. Because I'm using bimetal blade stock, I only heated the joints enough to turn them blue. I haven't used the blade I finally made (out of two pieces of too-short stock) enough to say whether it will stand up to hard use, but the joints look good and didn't break when repeated bent to a 4" radius.

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