Announcement

Collapse
No announcement yet.

4X6 Band Saw Blade Tension

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • 4X6 Band Saw Blade Tension

    I have had one of these for over twenty years and never figured out how to properly tension the blade. There must be some guidance somewhere. Now I have two and I just bought a new blade and think it is time that I found out the right tension for these. Does anyone have some trick or insight on this. On my wood cutting bandsaw there is a indicator sitting on top of the blade tension spring. While not anywhere near 100% accurate, it does give a starting point.
    Thanks
    Peter
    Grantham, New Hampshire

  • #2
    I just crank on it as hard as I can with the little wheel it has, then adjust tracking. Supposedly the blade should make a nice pinging sound when you flick it.

    Comment


    • #3
      Originally posted by mattthemuppet View Post
      I just crank on it as hard as I can with the little wheel it has, then adjust tracking. Supposedly the blade should make a nice pinging sound when you flick it.
      Yup, works for me too, although not very much of a repeatable standard I agree.Only way I can think of to make it a standard would be to adapt a torque wrench to one adjusted "correctly" so that one will then on have a number to shoot for.

      Long time ago someone told me to get it as tight as you can using the little adjustment hand-wheel on the blade tensioner without tools, and it has been good to me since.
      Now I know I can make it much tighter this way than some and no doubt there are others that can make it tighter than me. Give it a good snugging and see if you can achieve that "ping".
      Home, down in the valley behind the Red Angus
      Bad Decisions Make Good Stories​

      Location: British Columbia

      Comment


      • #4
        I read an advisory that said that you tighten by hand till it does not turn. The theory being that the small diameter knob only gives you a certain amount of leverage. If doing it "right" you measure the deflection when pushed in the middle of the span. 1/4 to 1/2 inch should be OK.

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

        Location: SF East Bay.

        Comment


        • #5
          You do not mention the most important aspect of this, the size of the blade, a .060" X 1" blade will need more tension then a ,030" X 3/8" blade.

          The blade manufacturer will recommend a blade tension. Use a blade tension gauge if you are obsessed with measuring it.
          https://www.amazon.com/Starrett-682E...VGRB3Z2TDA2V04
          Last edited by Bented; 07-17-2020, 06:40 PM.

          Comment


          • #6
            The generic 4X6s all use a 1/2" blade, usually .025 thick. 'As tight as you can' seems a bit much to me. I get them pretty tight and check by feel, pinching the blade back toward the frame on the 'top' run, opposite the cutting side. It is very subjective, of course. In any case, too tight is probably better than too loose. By comparison, the bigger saw at work uses a hydraulic tensioner and the spec pressure is 875psi. That's for a 1" .060ish blade. That spec doesn't mean anything, though, without knowing the acting piston area but it is really tight!
            Last edited by chipmaker4130; 07-17-2020, 06:50 PM.
            Southwest Utah

            Comment


            • #7
              A blade gauge such as is found on a typical home shop saw that simply measures the length of the blade is meaningless unless all your blades are exactly the same length, width, and thickness. Most saws will accept blades with a variation in length of an inch or more. Even with identical blades, without a reference to a particular "standard" blade, a gauge won't mean much. "tight as you reasonably can" and "ping" has also worked fine for me.
              Last edited by mickeyf; 07-17-2020, 07:57 PM. Reason: clarified gauge type
              "A machinist's (WHAP!) best friend (WHAP! WHAP!) is his hammer. (WHAP!)" - Fred Tanner, foreman, Lunenburg Foundry and Engineering machine shop, circa 1979

              Comment


              • #8
                I do not know what the newer 4 x 6 cutoff saws have ( 1990 + in age)
                Mine was purchased in the early 80's and was from Taiwan
                The problem with these saws ( and may be true today ??) is the adjustment tension screw is a
                a solid screw with handle , so there is no shock absorber to handle minor issues
                You need to spring load the idler wheel !
                I made the screw ( threaded rod) locked in the idler wheel block.
                Put a Chevy Valve spring ( Chevy 4cyl ) with a heavy washer and Nut between the housing and a new threaded knob ( Safety protector , no function really)
                Now I tighten the heck out of it and the blade stays on ( did the above in 1985) and a nice "ping" comes with plucking the blade
                The threaded rod allows me to use weights for cutting, I add a brass ring or two/three to the rod to get correct cutting preload
                Rich

                Click image for larger version

Name:	P7170024.JPG
Views:	210
Size:	687.2 KB
ID:	1887634Click image for larger version

Name:	P7170027.JPG
Views:	209
Size:	696.3 KB
ID:	1887635Click image for larger version

Name:	P7170028.JPG
Views:	185
Size:	698.0 KB
ID:	1887636
                Green Bay, WI

                Comment


                • #9
                  I will adjust tension in a hacksaw and get a feel for what is 'enough', then try to get the same feel on the band saw. Same blade pretty much. If I can saw properly with a hacksaw without rolling the blade, then it should be about the same for the band saw. If I crank the knob by hand, I find it easy to get it too tight. I'm just pinching a bit of the blade between my fingers, and gauging tension from that. I've never needed to use a gauge or get fancy with anything.
                  I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

                  Comment


                  • #10
                    tighten as much as you can with two hands and the saw running.

                    Comment


                    • #11
                      I disagree that bandsaw tension gages are meaningless. Arguments based on physics notwithstanding, I find it laughable that Starrett would have sold an expensive instrument for many decades if it gave meaningless results.

                      metalmagpie

                      Comment


                      • #12
                        Too low of a tension will result in the blades breaking from flexing. And moderately too low will cause rough finishes on bigger bars due to the blade flexing and wandering when it tries to arch up from the pressure and this causes the portion along the teeth which are under compression to buckle back and forth. When you have "enough" you'll get nice fairly smooth cuts and the blade will last long enough to dull the teeth to where it worries its way through the metal taking four or more times as long to cut as it did when new.

                        For me this is pretty tight but not "as tight as I can turn the knob" where it leaves my hand hurting for a few seconds. Sound wise these are bigger blades so I go for more of a base like "pong!" sound when plucked. This has proven to be enough tension to stay in place for MOST cuts. The odd time the blade will jump off the wheels on me due to me using it in the vertical mode and pushing the work too firmly. But that's me getting greedy. I regularly wear out the blades and when inspected I think there was just one of them which showed signs of cracking in some of the tooth gullets. This sort of cracking is a sign of not enough tension normally. But since it only happened the one time I chalked it up to a poor blade.

                        Here is A LINK to an online piano keyboard to get a feel for the sound. I just checked and the knob is tight enough that it took a good effort to make it move at all. And the blade has a tone that is a pretty close match to the third white key to the left of the one marked "Q".
                        Chilliwack BC, Canada

                        Comment


                        • #13
                          Measure deflection over span, x.xxxx units of deflection divided by x.xxxx units of span (D/S) = blade tension. Consult the blade manufacturer for the DS ratio of a particular blade, they will be happy to hear from you.

                          Place an indicator on the beam with the plunger against the back of the blade, run the feed down with the blade stopped until it touches off on the sample much like setting the Z axis position of a tool in a mill. Advance the feed 1/2 of the tooth gullet depth and the indicator will give you the deflection.

                          A manufacturer may recommend a DS of .0005" per inch of span, therefore a 4" span will result in .002" of deflection at the center.

                          Last edited by Bented; 07-18-2020, 12:56 PM.

                          Comment


                          • #14
                            I have to laugh at some of the comments, my own being at the top of the list.

                            As tight as you can, but not as tight so as to hurt your hand, you are only using one hand aren't you?
                            But hey, not as tight as that big knuckle dragging goon over there, yet way tighter than that limp wristed wimp over there.

                            Push till you get 1/4-1/2 inch of deflection, ok how hard should I have to push to get that much?

                            Then there are the musical comparative analogies. Ping, pong, bing, but no buzz or twang. LOL

                            A fairly nebulous subject with lots of anecdotal advice tempered with years of good and sound experience tells me that the OP is no less or more wiser than any of us in regards to setting his bandsaw's blade tension properly.
                            Do what works best using all of the above good, albeit ambiguous, advice.

                            Just for yucks I looked at Grizzly's recommendations regarding setting blade tension for their 4x6 saw and this is what they said.

                            Using moderate finger pressure, push against
                            the side of the blade. The blade should not
                            move more than 0.004".
                            They also mentioned this.

                            Note: We recommend using a blade
                            tensioning gauge, like the one found in
                            ACCESSORIES on Page 28. If you use this
                            option please follow the instructions included
                            with your gauge.
                            The blade tension gauge shown is a very nice Lenox blade tension gauge.
                            I concur that any of the very nice blade tension gauges made by Morse, Starrett, Lenox, etc.are great tools that will meet a repeatable and recognized industry standard.
                            I also think we can all agree that spending $350-$600 on such a luxury for a blade on a $200 saw is probably not the wisest move.

                            In summation I would just suggest doing what you have done for the last twenty years, tempered with some of the very good but often times ambiguous advice left here. We've all had good service from these little saws so I don't think it is really all that critical. It has been one of my best investments for the shop. Use good quality bi-metal blades, dial in the tracking and blade guides and enjoy the saw. Blades have lasted me longer than I have any right to expect in spite of not adhering to a "standard".
                            Home, down in the valley behind the Red Angus
                            Bad Decisions Make Good Stories​

                            Location: British Columbia

                            Comment


                            • #15
                              Originally posted by Willy View Post

                              The blade tension gauge shown is a very nice Lenox blade tension gauge.
                              I concur that any of the very nice blade tension gauges made by Morse, Starrett, Lenox, etc.are great tools that will meet a repeatable and recognized industry standard.
                              I also think we can all agree that spending $350-$600 on such a luxury for a blade on a $200 saw is probably not the wisest move.
                              Well put.
                              However home shop hobby machinists seem to prefer solid numbers.
                              Such as blade tension should only be set to 237.05 +.000 -.001 Newton/Pascals per unit of width, This eliminates the tuning forks and hand pain however so this is a good thing, to coin a phrase, Going Forward.
                              Last edited by Bented; 07-18-2020, 02:44 PM.

                              Comment

                              Working...
                              X