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  • Bandsawing Woes

    Was recently cutting some 3" round nylon stock on my asian 5X6 H/V saw, and it would cut ok til about the point where the blade is fully buried. Then all progress would seem to come to a complete halt.

    By hanging some weight on the end of the arm I could make it cut, but then the cut would start leading off to one side.

    Now, my diagnosis of the problem was that the 18tpi blade was loading up. That blade seems to cut steel as normal, so I don't think it's worn out. But running my fingers along the sides, I do seem to detect a little more aggressive 'set' on the side that was leading. ...but that may be my imagination.

    At any rate, what's the collective judgement of you folks? Would a coarser blade solve all my woes?
    And what's the coarsest blades available in that 1/2" X 64 1/2" size? I think 14tpi is the coarsest I've found.

    BTW, I moved over to my wood cutting saw, and it cut fine for about 5 or 10 seconds til the melting slag starting grabbing the throat plate.
    Lynn (Huntsville, AL)

  • #2
    I think you're right -- the problem is the blade is loading up. You might try a blast of air on the blade just as it's leaving the cut, to blow the sawdust from between the teeth.
    ----------
    Try to make a living, not a killing. -- Utah Phillips
    Don't believe everything you know. -- Bumper sticker
    Everybody is ignorant, only on different subjects. -- Will Rogers
    There are lots of people who mistake their imagination for their memory. - Josh Billings
    Law of Logical Argument - Anything is possible if you don't know what you are talking about.
    Don't own anything you have to feed or paint. - Hood River Blackie

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    • #3
      lynnl,

      Just curious, what happens when you reduce the bandsaw speed and cut the nylon slower?

      _______________________



      [This message has been edited by Mike Burdick (edited 01-26-2006).]

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      • #4
        Absolutely right on the load up.
        4 TPI is much better for 3" stock.

        A way to che - - er work around, is to slightly roll you stock as you cut so that you cut a spiral on the way in.

        A good rule of thumb is to allow one and a half to two and a half teeth on the work for thin stock, and if you have more than ten- fifteen you pay attention to possible load-up, chip jamming.

        HTH ag

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        • #5
          A lot of plastics have a lot of "sqwish" compared to metal and wood. I have a bandsaw with electronic variable speed, use a wood blade at a slow (metal) speed. Try to find a speed/tooth combo that won't melt it, but fast enough clear chips, also check the "down feed" pressure, it may be bending the stock into the kref.
          Sorry can't be more specific, I cut plastic "seat of pants" style.

          ------------------
          Today I will gladly share my experience and advice, for there no sweeter words than "I told you so."
          Today I will gladly share my experience and advice, for there no sweeter words than "I told you so."

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          • #6
            Lynnl, I have a 6 tpi blade for my 4x6 h/v saw that I believe I got from Enco. I have used it to cut pvc pipe, wood and aluminum successfully. I am not sure the saw has the guts to pull it through steel so I usually just use a 10 to an 18 pitch, whatever is on the saw. I have ordered 10tpi, 14 tpi and 18 tpi and I believe someone makes a 20 tpi but usually a 14 takes care of most of my needs.
            Jonathan P.

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            • #7
              I use a VP 5-8 TPI blade for everything over 1/2" and a Raker 14 TPI blade for everything under 1/2".

              -Adrian

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              • #8
                <font face="Verdana, Arial" size="2">Originally posted by Mike Burdick:
                lynnl,

                Just curious, what happens when you reduce the bandsaw speed and cut the nylon slower?

                _______________________

                [This message has been edited by Mike Burdick (edited 01-26-2006).]
                </font>
                (oops - put this inside Mike's "quotes" first try)

                To tell the truth I didn't try the slowest speed. I have it set in the mid range, and I didn't think dropping it down would make much difference, considering how bad it was doing.

                I did try holding a brass brush against the teeth in hopes of clearing the chips some, but it didn't seem to help much. ...they're kinda clingy chips. More dust-like actually.

                I think I'm gonna have to find some coarser blades to keep on hand. I'm seldom cutting anything less than .5" anyway.


                [This message has been edited by lynnl (edited 01-26-2006).]
                Lynn (Huntsville, AL)

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                • #9
                  Do you get chips still? Or do you have a melting problem?

                  If it is a spring or weight fed unit, it could be biting in too deep and loading up. If you reduced the feed pressure etc it might work better.

                  Plastics that melt are a real problem. Sometimes the cut itself doesn't melt them, but the rubbing of the blade and the chips along the cut walls does. Then the chips may weld up to the side of the cut and the blade ends up having to cut the same chip multiple times.

                  If the saw is worn so the set is less on one side, it may wander, and it may also make more heat because it rubs. It rubs because its a little dull, and because the cut isn't as wide.

                  The set should prevent the blade from rubbing much by making a wider cut.
                  1601

                  Keep eye on ball.
                  Hashim Khan

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                  • #10
                    Yes on the less tpi.

                    A few years ago I tried to saw some 6" brass stock. The people I get blades from recomended 4 tpi. Even that took a long to time to saw thru and it would not track straight.

                    Gary
                    Gary Davison
                    Tarkio, Mo.

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                    • #11
                      Little chips and dust clinging to the blade might also be static elec charge with some plastics. I don't have a good way around that, but I have used those dryer sheets/spray. Don't know your specifics, and possible later problems(chem interaction, finish, etc.) it may cause you.

                      ------------------
                      Today I will gladly share my experience and advice, for there no sweeter words than "I told you so."
                      Today I will gladly share my experience and advice, for there no sweeter words than "I told you so."

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                      • #12
                        Nylon has some interesting properties. It has a high coefficient of thermal expansion but very poor conductivity. When cutting or drilling it tends to heat with nowhere for the heat to go. This causes it to break the "rules" and expand inward. This can pinch the blade or tool and cause more heating which will melt the chips to the tool or blade. Try using water with a few drops of soap as a cutting fluid. This will keep it cool.
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                        • #13
                          No, there didn't appear to be any melting with the h/v saw. Certainly was w/the 14" woodsaw tho.

                          W/the high humidity here in the Nth Ala. static charge is seldom a problem.

                          Now I did not try reducing the feed pressure (it's spring counterbalanced). That might've helped. Didn't think of that.

                          It would seem to cut fine for that first 1/2", then as the kerf grew longer it would just rub ...more of a sanding action.

                          The blade seems sharp to the touch. But it's certainly not a new one. In fact it's one I'd brazed back together once.
                          Lynn (Huntsville, AL)

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                          • #14
                            Try some coolant anyway. I used to use ethanol since it doesn't attack plastics or machines but my supply has run out.
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                            • #15
                              I tried a little Tap Magic on it. That sure didn't help any.

                              I don't need to cut anymore now. When I finally got it cut down to size I just chucked it up in the lathe and faced it off. Sure cuts nice on the lathe.
                              Lynn (Huntsville, AL)

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