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How to set blade tension on 4X6 bandsaw?

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  • How to set blade tension on 4X6 bandsaw?

    I'm obviously doing something wrong.
    I keep snapping bandsaw blades on my little 4 X 6 bandsaw.
    The roller guides are gapped to .030, and I buy .025 thick blades, so they're not getting pinched.
    I'm cutting 2.5" round 1018 steel on slowest speed.
    But how do I correctly set the blade tension?
    Right now I tighten it by hand, then give it a good 'tweek', about 1/4 turn.

  • #2
    I would suspect the band saw blade rather than the saw at this point. I bought some band saw blades for a" portaband" a while back and even though they were a good brand, five of six blades broke within a minute of use. I took them back and the folks swapped them out for another brand. I am thinking it was just a bad batch.

    rollin'

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    • #3
      you mean they breake? i have not yet managed to do that. i tighten as much as i can. weird. i also suspect its the blades.

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      • #4
        Can you tell if they are breaking at the weld joint or not? I try to run them as tight as necessary but don't go crazy on tension unless they are slipping. I usually buy blades in 100-250 feet length and weld or silver soldier them myself so only have me to blame if it's the weld. Also buy good quality blades as like mentioned may be brand/batch failure.

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        • #5
          They last about 2 weeks on average. Usually they'll slip off one or two times, then they snap in two. It appears to be at the weld.
          I was just wondering how tight I should set them.
          'Dog-Pi$$ Jones' tight, or just hand tight with a bit of flex still left in them?

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          • #6
            I also set my blade tension really tight and crank down on the knob pretty good.

            When I first got my bandsaws both of them would slip on occasion or slip and break.
            Ever since I started keeping the tension really tight, I very rarely have ANY problems.

            It could very well be the blades as others have said. Try a different brand and experiment with tension to find what works best for your machine.

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            • #7
              I checked into this because I've had one break. My conclusion was that I don't think a typical 4x6 bandsaw can apply enough tension to snap a blade, given that other alignments are correct. You need about 20x the recommended tension to break a blade just from tension.

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              • #8
                I had some problems with my 4x6 as well with blades breaking, always at the weld. I cut a mixture of brass and steel for the most part.

                I know for the amount that I use it, I was not wearing the blades out and dulling them. I don't have a average time, but it was enough that I was nervous if I didn't have a spare blade handy and would order 2 at a time. I tried several brands, teeth per inch, etc and never really noticed an appreciable difference between them. Given the time frame, multiple venders, etc, it was not as simple as a bad batch of blades.

                I found the best way to tighten the blade was just enough that it didn't slip cutting stock, plus a 1/8 - 1/4 turn or so. I have been using the same blade now over a year and what I do now includes using the saw more.

                You may not be able to break a blade simply from tightening it in these cheap small saws, but you can tighten it enough that you get premature blade breakage from being too tight.
                Last edited by baldysm; 05-30-2012, 05:37 PM.

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                • #9
                  I just broke a blade yesterday. It has been the longest lived blade ever, so far. It's a lennox diemaster II, and was about 50% more expensive than any other I've had, but has lasted about four times as long. It did not break at the weld. I suspect that I weakened it when it jammed in something I was cutting.

                  I keep it quite taut, kind of like a guitar string. I also have played with the saw a lot, aligning and adjusting so the wheels are parallel when the tension is on.

                  I would suggest to give the saw a bit of a re-build prior to mounting a blade. I would start at the bottom wheel- it should turn normally without much wobble, and there should not be much play in the shaft- if there is, you may never get a blade to stay on properly. Then go to the top wheel- clean and lube the adjusting threads, find and experiment with the wheel tilt adjustment. You can place a straightedge across the wheels to check- a carpenters level will be good enough for this.

                  Then remove the blade guides temporarily and mount a blade. You would adjust for tilt and tension at the same time, as one affects the other. When you have significant tension on the blade, and it stays against the flanges on the wheels when running, but does not grind against the flanges, then the tilt will be about right. The blade should be tracking well. If the blade is moving in and out as it goes around, it's probably toast. All the suggestions from people that say use a good blade are well-founded. It's cheaper in the long run, and less frustrating.

                  So with the blade tracking nicely under tension, you can re-instal the guides. The back of the blade should just touch the rear bearings, and like you say, there should be a bit of gap between the guide bearings so the blade isn't pinched as it passes between them. Now you fiddle with the alignments of the guide bearings, etc.

                  We haven't decided on the proper blade tension yet, nor found a way to set it to that tension. I like to crank it up til it is starting to sing, then bring it up a bit more. That's pretty vague, but it's better than 'crank it up as tight as you can'. With the tension adjustment cleaned up and lubed, it doesn't take 'all the hand power you have' to reach a suitable tension. If you never have lubed the adjustment, then it might take all your hand power to get you there. Still vague. Maybe make a few cuts in some steel with a hacksaw, and set the tension so the blade doesn't twist when you're sawing. Then use a two finger plus thumb method to gauge the tension. Set your bandsaw blade to about the same tension.
                  I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

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                  • #10
                    I bet the wheels are not coplanar so the blade is being bent in the wrong axis, ie back to front, rather than side to side, if you see what I mean...

                    That will pop the weld open pretty quick.

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                    • #11
                      I tighten my 4X6 as much as I can by hand, considered replacing the knob with a hex nut so I could get a "little" more on it. I weld all my blades from pieces from work that are too short for the saws we use there. I've done all the 4X6 mods and adjustments that I am aware of. My thought is that is difficult to get too much tension on this saw. Bob F.

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                      • #12
                        I can only offer my experience in breaking a blade on my 4x6 once... It was the blade that the saw came with, a quality name (Lenox). I was quick to blame the saw; it had always been difficult to adjust. The tension was always very tight when the blade was mounted. When I bought a second blade (Starrett), I realized that my troubles were actually caused by a too-short blade length of the initial blade. It was labeled and supplied correct... but it was way too short. I've read many complaints since of improper blade lengths in relation to what was purchased and, often enough, labeled.

                        I might also mention that you might want to keep the tension fairly loose for a good time when first installing a blade. Blade "break in" is very real, I have found. Those very sharp teeth when the blade is new can cause the blade to get caught up in the cut, snag, etc. until they dull a bit. Run the blade looser than you might, keep the slowest speed for everything and easy up on the downfeed if you have a hydraulic piston on yours. Give it a couple weeks. After that, I would argue you can tighten that blade up as taught as you would ever like, and it will be just fine. They're funny that way. This is all just info I have gleamed from using mine. Take it for what its worth
                        Last edited by Arthur.Marks; 05-30-2012, 07:04 PM.

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                        • #13
                          Bandsaw blade tension questions i have seen asked many times both on metal and wood saws.
                          I have yet to see a simple solution to this, there seem to be 100 different approaches from 100 different users.

                          What is needed on these saws (of any type), is an accurate gauge of some sort that can be set for gauge thickness etc.
                          I have yet to break a blade over 12 years, i use good blades,,AND, i ALWAYS slack the tension off after i'm finished cutting.
                          To re-tension the blade i simply just tighten , but NOT over tighten and twang the blade untill i think it's about right.
                          What is right???? I don't really know, i know i never get it exactly the same each time, but so far it has worked ok for me.
                          I think slacking off the tension is important when a cut is finished.

                          Maybe someone knows of a good method??

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                          • #14
                            The saw shouldn’t jam and slip. A blade that is to fine for the cross section being cut can pack the gullets and jam. 8-12 teeth in the material is ideal with a Max. of about 24. Down force should be no more than about 8 pounds as measured at the handle. At this weight, unless your saw has hydraulically controlled feed, the saw will need some minding at the beginning and end of the cut. I feel that the wheels on these saws are a little small and this can lead to fatigue cracking. To be on the safe side, don’t let the saw run needlessly without doing work and a flex back blade is probably a good choice.
                            Good luck, Mike

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                            • #15
                              (I think) that the manual that came with my standard 6 x 4 band-saw said that the gap at the guide rollers was 0.001" - so I set it to 0.000>0.001" and it seems to work pretty well. Cuts are straight, square and not bowed.

                              The tilt of the upper wheel is important as well as it determines where the blade runs on the flanged steel wheel.

                              All of the settings are in the hand-book and though a bit hard to follow at times ("Chingalish") it does the job well enough.

                              I "set and forget" my blade speed setting to "Low" - and there it stays.

                              I hand-feed (drip) tapping oil onto my blade as it is running. I hand control the vertical feed until I have a cut 3>4 teeth long and let the spring tension feed take it from there.

                              I can afford the time as I am retired and so have plenty of it and I only work on one machine at a time.

                              The dealer I bought it from suggested that I get rid of the blade that came with it and to use "Starrett" or "Lennox" - which I did and do.

                              Mine does not get a lot of use as some here do but it works well enough.

                              If it ever needed a lot of work or a re-build I'd replace it as they are pretty cheap.
                              Last edited by oldtiffie; 05-30-2012, 09:20 PM.

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