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Cupping problem when cutting heavy wall steel tubing

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  • bryanc.smith
    I really tuned the bandsaw in tonight after installing the new blade I bought from Enco. It s a 14 tpi Irwin blade. I got the saw really dialed in, I mean
    Message 1 of 8 , Apr 14, 2009
      I really tuned the bandsaw in tonight after installing the new blade I bought from Enco. It's a 14 tpi Irwin blade. I got the saw really dialed in, I mean very close to dead nuts square (at least on this 1 3/4" .250" wall tubing).

      I noticed a problem though and I was wondering what you guys thought about it. As the blade cuts through the wall far enough to penetrate the ID (so that it is then effectively making two separate cuts of either wall) the blade begins making a "cupped" cut of the two walls of tubing. The cut is perfectly straight all the way until the blade breaks through into the ID and then the face of both cut walls show a pretty obvious radius that continues along the cut until the blade completes the cut through the ID and then takes a single cut through the rest of the tubing.

      If you were to stand directly above the saw and look down at the cut you would see the two walls scalloped in a concave manner as this crude drawing shows:
      | ___ | | ___ |
      | --- --- | | --- --- |
      |---- ----| |---- ----|

      Of course it is not this dramatic, it's only slight cupping, but enough to notice.

      I'm running the saw at the slowest speed now, the blade is tensioned as tightly as I can get it by hand (I usually tighten it until I get a "twang" that sounds right), and the blade is listed on Enco as an Irwin "10-14" TPI blade.
    • Keith Green
      Offhand, I would say too heavy a feed. Might be OK for the thick part but when it breaks through into the walls the effective area of the blade becomes less so
      Message 2 of 8 , Apr 14, 2009
        Offhand, I would say too heavy a feed. Might be OK for the thick
        part but when it breaks through into the walls the effective area of the
        blade becomes less so the feed increases and causes the blade to deflect.


        Keith

        bryanc.smith wrote:
        > I really tuned the bandsaw in tonight after installing the new blade I bought from Enco. It's a 14 tpi Irwin blade. I got the saw really dialed in, I mean very close to dead nuts square (at least on this 1 3/4" .250" wall tubing).
        >
        > I noticed a problem though and I was wondering what you guys thought about it. As the blade cuts through the wall far enough to penetrate the ID (so that it is then effectively making two separate cuts of either wall) the blade begins making a "cupped" cut of the two walls of tubing. The cut is perfectly straight all the way until the blade breaks through into the ID and then the face of both cut walls show a pretty obvious radius that continues along the cut until the blade completes the cut through the ID and then takes a single cut through the rest of the tubing.
        >
        > If you were to stand directly above the saw and look down at the cut you would see the two walls scalloped in a concave manner as this crude drawing shows:
        > | ___ | | ___ |
        > | --- --- | | --- --- |
        > |---- ----| |---- ----|
        >
        > Of course it is not this dramatic, it's only slight cupping, but enough to notice.
        >
        > I'm running the saw at the slowest speed now, the blade is tensioned as tightly as I can get it by hand (I usually tighten it until I get a "twang" that sounds right), and the blade is listed on Enco as an Irwin "10-14" TPI blade.
        >
        >
        >
        > ------------------------------------
        >
        > Yahoo! Groups Links
        >
        >
        >
        > ------------------------------------------------------------------------
        >
        >
        > No virus found in this incoming message.
        > Checked by AVG - www.avg.com
        > Version: 8.5.287 / Virus Database: 270.11.57/2059 - Release Date: 04/14/09 14:52:00
        >
        >
      • legaltec@comcast.net
        I would have to agree with Keith, Usually when you have any inadequency with cutting it contributed to the feed or the tension. It doesnt appear that the
        Message 3 of 8 , Apr 15, 2009
          I would have to agree with Keith, Usually when you have any inadequency with cutting it contributed to the feed or the tension.  It doesnt appear that the tension is the problem, try slowing the feed down.


          ----- Original Message -----

          From: Keith Green

          To: 4x6bandsaw@yahoogroups.com

          Sent: Wed, 15 Apr 2009 05:08:01 +0000 (UTC)

          Subject: Re: [4x6bandsaw] Cupping problem when cutting heavy wall steel tubing































              


                      

                

              Offhand, I would say too heavy a feed. Might be OK for the thick


          part but when it breaks through into the walls the effective area of the


          blade becomes less so the feed increases and causes the blade to deflect.





          Keith





          bryanc.smith wrote:


          > I really tuned the bandsaw in tonight after installing the new blade I bought from Enco.  It's a 14 tpi Irwin blade.  I got the saw really dialed in, I mean very close to dead nuts square (at least on this 1 3/4" .250" wall tubing).  


          >


          > I noticed a problem though and I was wondering what you guys thought about it.  As the blade cuts through the wall far enough to penetrate the ID (so that it is then effectively making two separate cuts of either wall) the blade begins making a "cupped" cut of the two walls of tubing.  The cut is perfectly straight all the way until the blade breaks through into the ID and then the face of both cut walls show a pretty obvious radius that continues along the cut until the blade completes the cut through the ID and then takes a single cut through the rest of the tubing.


          >


          > If you were to stand directly above the saw and look down at the cut you would see the two walls scalloped in a concave manner as this crude drawing shows:


          > |       ___       |             |       ___       |


          > |    ---   ---    |             |    ---   ---    |


          > |----         ----|             |----         ----|


          >


          > Of course it is not this dramatic, it's only slight cupping, but enough to notice.


          >


          > I'm running the saw at the slowest speed now, the blade is tensioned as tightly as I can get it by hand (I usually tighten it until I get a "twang" that sounds right), and the blade is listed on Enco as an Irwin "10-14" TPI blade.


          >


          >


          >


          > ------------------------------------


          >


          > Yahoo! Groups Links


          >


          >


          >


          > ----------------------------------------------------------


          >


          >


          > No virus found in this incoming message.


          > Checked by AVG - www.avg.com


          > Version: 8.5.287 / Virus Database: 270.11.57/2059 - Release Date: 04/14/09 14:52:00


          >


          >  











              
            



              

              

              

              




        • bryanc.smith
          The diagram didn t work, lol. All of my spaces dropped out. I ll try to snap a picture later. I ll take a couple cuts with a lighter feed and see what
          Message 4 of 8 , Apr 15, 2009
            The "diagram" didn't work, lol. All of my spaces dropped out. I'll try to snap a picture later. I'll take a couple cuts with a lighter feed and see what that does.

            I'm wondering if the level of tension I'm using is causing vibrations in the blade that are causing this. I'll loosen it up a bit after I try the lighter feed.

            --- In 4x6bandsaw@yahoogroups.com, Keith Green <ksgg@...> wrote:
            >
            > Offhand, I would say too heavy a feed. Might be OK for the thick
            > part but when it breaks through into the walls the effective area of the
            > blade becomes less so the feed increases and causes the blade to deflect.
            >
            >
            > Keith
            >
            > bryanc.smith wrote:
            > > I really tuned the bandsaw in tonight after installing the new blade I bought from Enco. It's a 14 tpi Irwin blade. I got the saw really dialed in, I mean very close to dead nuts square (at least on this 1 3/4" .250" wall tubing).
            > >
            > > I noticed a problem though and I was wondering what you guys thought about it. As the blade cuts through the wall far enough to penetrate the ID (so that it is then effectively making two separate cuts of either wall) the blade begins making a "cupped" cut of the two walls of tubing. The cut is perfectly straight all the way until the blade breaks through into the ID and then the face of both cut walls show a pretty obvious radius that continues along the cut until the blade completes the cut through the ID and then takes a single cut through the rest of the tubing.
            > >
            > > If you were to stand directly above the saw and look down at the cut you would see the two walls scalloped in a concave manner as this crude drawing shows:
            > > | ___ | | ___ |
            > > | --- --- | | --- --- |
            > > |---- ----| |---- ----|
            > >
            > > Of course it is not this dramatic, it's only slight cupping, but enough to notice.
            > >
            > > I'm running the saw at the slowest speed now, the blade is tensioned as tightly as I can get it by hand (I usually tighten it until I get a "twang" that sounds right), and the blade is listed on Enco as an Irwin "10-14" TPI blade.
            > >
            > >
            > >
            > > ------------------------------------
            > >
            > > Yahoo! Groups Links
            > >
            > >
            > >
            > > ------------------------------------------------------------------------
            > >
            > >
            > > No virus found in this incoming message.
            > > Checked by AVG - www.avg.com
            > > Version: 8.5.287 / Virus Database: 270.11.57/2059 - Release Date: 04/14/09 14:52:00
            > >
            > >
            >
          • Bill P
            Unless I m not understanding your problem, I ve found that the finer the teeth in a blade, and the lighter the load, the better the cut when dealing with thin
            Message 5 of 8 , Apr 15, 2009
              Unless I'm not understanding your problem, I've found that the finer the
              teeth in a blade, and the lighter the load, the better the cut when
              dealing with thin materials, especially conduit and thin walled pipe.
              Bill.

              bryanc.smith wrote:
              >
              >
              > The "diagram" didn't work, lol. All of my spaces dropped out. I'll try
              > to snap a picture later. I'll take a couple cuts with a lighter feed
              > and see what that does.
              >
              > I'm wondering if the level of tension I'm using is causing vibrations
              > in the blade that are causing this. I'll loosen it up a bit after I
              > try the lighter feed.
              >
            • bryanc.smith
              I took a picture of the cut since it s hard to explain. Here s the link: http://img100.imageshack.us/img100/4564/img1089medium.jpg You can see the cupping I m
              Message 6 of 8 , Apr 15, 2009
                I took a picture of the cut since it's hard to explain. Here's the link: http://img100.imageshack.us/img100/4564/img1089medium.jpg

                You can see the cupping I'm referring to. It differs on different cuts, sometimes it's one single concave indentation and other times it's wavy like the cut pictured.

                --- In 4x6bandsaw@yahoogroups.com, Bill P <NPWBill@...> wrote:
                >
                > Unless I'm not understanding your problem, I've found that the finer the
                > teeth in a blade, and the lighter the load, the better the cut when
                > dealing with thin materials, especially conduit and thin walled pipe.
                > Bill.
                >
                > bryanc.smith wrote:
                > >
                > >
                > > The "diagram" didn't work, lol. All of my spaces dropped out. I'll try
                > > to snap a picture later. I'll take a couple cuts with a lighter feed
                > > and see what that does.
                > >
                > > I'm wondering if the level of tension I'm using is causing vibrations
                > > in the blade that are causing this. I'll loosen it up a bit after I
                > > try the lighter feed.
                > >
                >
              • legaltec@comcast.net
                Thats is different, maybe its the type of blade sometimes for no apparent reason after reconditioning a machine blades just are compatible and the cuts arent
                Message 7 of 8 , Apr 15, 2009
                  Thats is different, maybe its the type of blade sometimes for no apparent reason after reconditioning a machine blades just are compatible and the cuts arent all that great.  Not sure why but its happened to me.  Check out www.cuttech.com

                  ----- Original Message -----

                  From: bryanc.smith

                  To: 4x6bandsaw@yahoogroups.com

                  Sent: Wed, 15 Apr 2009 19:34:59 +0000 (UTC)

                  Subject: [4x6bandsaw] Re: Cupping problem when cutting heavy wall steel tubing































                      


                              

                        

                  I took a picture of the cut since it's hard to explain.  Here's the link: http://img100.imageshack.us/img100/4564/img1089medium.jpg





                  You can see the cupping I'm referring to.  It differs on different cuts, sometimes it's one single concave indentation and other times it's wavy like the cut pictured.





                  --- In 4x6bandsaw@yahoogroups.com, Bill P wrote:


                  >


                  > Unless I'm not understanding your problem, I've found that the finer the


                  > teeth in a blade, and the lighter the load, the better the cut when


                  > dealing with thin materials, especially conduit and thin walled pipe.


                  > Bill.


                  >


                  > bryanc.smith wrote:


                  > >


                  > >


                  > > The "diagram" didn't work, lol. All of my spaces dropped out. I'll try


                  > > to snap a picture later. I'll take a couple cuts with a lighter feed


                  > > and see what that does.


                  > >


                  > > I'm wondering if the level of tension I'm using is causing vibrations


                  > > in the blade that are causing this. I'll loosen it up a bit after I


                  > > try the lighter feed.


                  > >


                  >











                      
                    



                      

                      

                      

                      




                • Jack
                  You can get that cupping when cutting solid steel as well. It seems to me that it is due to resonances between blade speed, blade vibration and the tooth
                  Message 8 of 8 , Apr 16, 2009
                    You can get that 'cupping' when cutting solid steel as well. It seems to me that it is due to resonances between blade speed, blade vibration and the tooth pitch. Try changing blade speed - up or down - the size and position of the pattern in relation to the 'entering' edge of the workpiece should change or (with luck) it may disappear altogether. Also, try adjusting the blade guide bearings so they hold the blade some tighter (both ends), and adjust the length of exposed blade.
                    Jack





                    --- In 4x6bandsaw@yahoogroups.com, "bryanc.smith" <rbcscapegoat@...> wrote:
                    >
                    > I took a picture of the cut since it's hard to explain. Here's the link: http://img100.imageshack.us/img100/4564/img1089medium.jpg
                    >
                    > You can see the cupping I'm referring to. It differs on different cuts, sometimes it's one single concave indentation and other times it's wavy like the cut pictured.
                    >
                    > --- In 4x6bandsaw@yahoogroups.com, Bill P <NPWBill@> wrote:
                    > >
                    > > Unless I'm not understanding your problem, I've found that the finer the
                    > > teeth in a blade, and the lighter the load, the better the cut when
                    > > dealing with thin materials, especially conduit and thin walled pipe.
                    > > Bill.
                    > >
                    > > bryanc.smith wrote:
                    > > >
                    > > >
                    > > > The "diagram" didn't work, lol. All of my spaces dropped out. I'll try
                    > > > to snap a picture later. I'll take a couple cuts with a lighter feed
                    > > > and see what that does.
                    > > >
                    > > > I'm wondering if the level of tension I'm using is causing vibrations
                    > > > in the blade that are causing this. I'll loosen it up a bit after I
                    > > > try the lighter feed.
                    > > >
                    > >
                    >
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