3100 cuts crooked when blade tilted

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  • JayStevans
    Forum Newbie
    • Mar 2007
    • 16

    3100 cuts crooked when blade tilted

    I'm having a problem with my BT3100.

    I'm trying to build a simple box, a speaker cabinet actually, to replace one my youngest managed to break.

    I tried cutting the sides to length with a 45 degree angle on the cuts, figured I would then glue them and use my nail gun to put in a couple pins to hold everything in place while the glue dried, plus some clamps.

    No so simple, as it turns out.

    You might wonder why, after several years of using this saw, I have never encountered this before. Well, I primarily build mission furniture which doesn't need angled cuts. At least not the pieces I've built.

    My problem is that when the blade is tilted at 45 degrees it cuts crooked - but not when at 90 degrees (straight up). The attached picture shows the situation.
    • Top left: shows a straight cut (blade at 90 degrees to the table top). The vertical edge of a plastic draftsman's triangle is aligned with the edge of the cut. The red oval outlines the area affected and the yellow line shows the cut. As you can see, the edge of the triangle is perfectly aligned with the edge of the cut, just as it ought to be.
    • Bottom left: same shot as top left but with the red oval and yellow line removed for clarity.
    • Top right: This also shows the long side of a draftsman's triangle placed along the edge of the cut. In this photo the yellow line follows the edge of the cut and the blue line the edge of the triangle.
    • Bottom right: same shot as top right but with the red oval, blue line, and yellow line removed for clarity. The edge of the cut is not parallel with the edge of the triangle, the cut actually angles away from the top edge of the plastic triangle.


    I hope the above is clear when combined with the pictures.

    I spent the morning going through the alignment processes for the sliding miter table (SMT) and fence. Each was off a bit, I corrected them as best I could (my digital caliper says I'm within a couple thousandths of an inch) and hoped my next test cuts would be perfect.

    Nope, same problem. Perhaps a little bit better but not much.

    I'd be less surprised if the cut was crooked when the blade was straight up AND when angled at 45 degrees. But straight up cuts work fine. Angled ones display this problem.

    My setup:
    • Using SMT to push the wood through the blade
    • No clamps being used to hold the wood in place that might warp it or lift it off the table
    • Not running the wood against the fence, it isn't even touching the wood


    I do not understand what's wrong, what problem could produce perfect cuts when the blade is straight up but crooked ones when the blade is angled 45 degrees?

    I'd welcome any wisdom this group might have to offer.

    Thanks.

    Jay
    Attached Files
  • cabinetman
    Gone but not Forgotten RIP
    • Jun 2006
    • 15218
    • So. Florida
    • Delta

    #2
    A few suggestions...

    The SMT isn't aligned to the blade.

    Stock could be shifting on the SMT.

    Operator not making positive passes.

    Try using the fence instead if possible.

    .

    Comment

    • JayStevans
      Forum Newbie
      • Mar 2007
      • 16

      #3
      Thanks for the quick reply, most appreciated.

      Regarding alignment of the SMT
      - if that is the case why would cuts with the blade at 90 degrees to the table top come out right? Wouldn't all cuts display the same problem?


      Regarding stock shifting
      - I have checked, don't believe that to be the case but will run some more through to see.
      - But again, why would 90 degree cuts come out fine and 45 degree ones bad?

      Regarding "Operator not making positive passes"
      - I do not know this term, could you please clarify?

      Using the fence
      - These are long pieces, hard to do using the fence
      - Might be worth running some shorter ones through though to test is the cuts come out straight, that'd at least put suspiscion on the SMT


      Thanks again. Headed back to the basement!

      Jay
      Last edited by JayStevans; 01-01-2013, 04:59 PM.

      Comment

      • leehljp
        Just me
        • Dec 2002
        • 8429
        • Tunica, MS
        • BT3000/3100

        #4
        Jay,

        You said you are cutting long boards, are you ripping them long with the 45° bevel? How are you doing this without a rip fence?

        Usually cutting lenght wise is done best with a rip fence. My only idea of what is happening is that the SMT, if that is what you are using, the SMT is rocking a smidgen as you push it.

        1. The SMT is probably 1/64 to 1/128 ABOVE the level of the saw table. Rocking can happen.

        2. Which side of the blade are you cutting it on? The left side or the right side? The right side would be dangerous as it would trap the cut. Either way, it has been my experience that the feed technique requires a good bit of experience with long 45° cuts/rips. This is one of those times that making a cut on a mock board is very handy in determining the outcome. Experience becomes a friend.
        Hank Lee

        Experience is what you get when you don't get what you wanted!

        Comment

        • JayStevans
          Forum Newbie
          • Mar 2007
          • 16

          #5
          Sorry, I didn't explain it well. By "long" I meant 16" and I'm beveling the short ends, (cross cut) not lengthwise. So, they're not long rips, just 7".

          As the attached diagram shows, I'm cutting on the left side using the SMT.

          I'll check to see if the SMT is riding above the table surface, could be.

          Jay
          Attached Files

          Comment

          • LCHIEN
            Internet Fact Checker
            • Dec 2002
            • 20914
            • Katy, TX, USA.
            • BT3000 vintage 1999

            #6
            I'm not sure what I'm being asked. The pictures are too small and I can't figure out what i'm looking at.
            Is the gray thing on the left half the workpiece? Whats the significance of the stuff in back? Am I supposed to see a triangle in the pictures?

            WHat do you mean precisely by crooked? I presume the blade is tilted 45 to get a 45 dgree bevel cut. IS the bevel angle not 45 degrees, or is the miter cut not at 90 degrees to the long edge? Looking from the top is the piece a trapezoid?

            Laying a sQUare along the bottom edge does the thin edge of the bevel not be 90 to the bottom edge?
            IS the front OK, but the back side where its 135 degrees to the face, is this edge not 90 to the bottom edge, meaning the bevel has lost its setting of 45 as you fed the board, and the bevel is twisted?
            Last edited by LCHIEN; 01-01-2013, 07:42 PM.
            Loring in Katy, TX USA
            If your only tool is a hammer, you tend to treat all problems as if they were nails.
            BT3 FAQ - https://www.sawdustzone.org/forum/di...sked-questions

            Comment

            • leehljp
              Just me
              • Dec 2002
              • 8429
              • Tunica, MS
              • BT3000/3100

              #7
              Another thing to look for is compare the boards. A good flat board can fool you by being warped by 1/16 inch and not being noticed until too late. This has happened to me on a couple of occasions.

              1/4 inch warp will be noticeable and even 1/8 will too, but 3/32 to 1/16 are not that noticeable. Stack you boards back to back and see how flat they are relative to each other.
              Hank Lee

              Experience is what you get when you don't get what you wanted!

              Comment

              • big tim
                Senior Member
                • Mar 2006
                • 546
                • Scarborough, Toronto,Canada
                • SawStop PCS

                #8
                If I understand your problem correctly: Your cross cuts when made at a 45 degree angle of the blade do not come out square to the long edge of the board( as if your SMT fence is not set at 90 degrees to the blade). Since your cuts with the blade at 90 degrees ar OK; the only thing it can be is that the travel path of the SMT is either climbing or descending as you make the cut.
                If it is climbing or descending as you make the cut one of the long sides of the board will be longer than the other.
                Hope my explanation makes sense!
                Good luck

                Tim
                Sometimes my mind wanders. It's always come back though......sofar!

                Comment

                • JayStevans
                  Forum Newbie
                  • Mar 2007
                  • 16

                  #9
                  Yes, Tim. That's how I wish I'd phrased it.

                  I hadn't thought to see if the SMT is climbing or descending. I'll do that, and the test suggested by others, in the next few days. Regrettably, my Christmas-to-New-Year's break is at an end. Work demands my presence for the rest of this short week.

                  Thanks to all for the suggestions.

                  Comment

                  • JayStevans
                    Forum Newbie
                    • Mar 2007
                    • 16

                    #10
                    Hi Loring,

                    My apologies for the tiny images. I'd made the erroneous assumption they would open up large enough for to be seen. Sorry to frustrate your attempts to help me out.

                    Tim stated the problem well and gave me a useful path to hunt on. I'll check his suggestion out and then post again, probably Saturday next.

                    Thank you for the assistance.

                    Jay

                    Comment

                    • All Thumbs
                      Established Member
                      • Oct 2009
                      • 322
                      • Penn Hills, PA
                      • BT3K/Saw-Stop

                      #11
                      Don't know what kind of stock you're using but if it is bowed even slightly, a 45-degree cut will take the same degree of curve as the bow. The stock has to be perfectly flat for an angled cut like that to come out straight.

                      Comment

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