Blade tilt mechanism and squareness

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  • cgallery
    Veteran Member
    • Sep 2004
    • 4503
    • Milwaukee, WI
    • BT3K

    Blade tilt mechanism and squareness

    I notice that when I tilt my blade to 45-degrees, that the back of it tilts less (by approx. 1/100") than the front of it. Has anyone else ever seen this behavior?

    Still trying to track it down. But I've had this happen before. Cuts with the SMT or a miter accessory table are perfectly square when the blade is set to 90-degrees. When I tilt the blade to 45-degrees, the cuts are no longer square.

    Scratching my head as to what is going on.

    And ideas?
  • RayintheUK
    Veteran Member
    • Sep 2003
    • 1792
    • Crowborough, East Sussex, United Kingdom.
    • Ryobi BT3000

    #2
    The only thing that comes to my mind is that the actuating arm is under some sort of rotational tension, applying a twist instead of a straightforward perpendicular motion. The only thing I can think of to attribute this to is linked to the 45 degree mechanical stop on the inside of the case. If this was just a little overset (i.e., set at 44 degrees, but you wind the handle a little "vigorously" to achieve a front-of-blade 45 degrees, that may do it. Are you sure that the stop is correctly set? If it is and there's no real effort to swing the blade when reaching the 45 degree position, I don't know what else it could be, apart from wear on the blade carrier rear pivot bolt.

    Ray.
    Did I offend you? Click here.

    Comment

    • cgallery
      Veteran Member
      • Sep 2004
      • 4503
      • Milwaukee, WI
      • BT3K

      #3
      Originally posted by RayintheUK
      The only thing that comes to my mind is that the actuating arm is under some sort of rotational tension, applying a twist instead of a straightforward perpendicular motion. The only thing I can think of to attribute this to is linked to the 45 degree mechanical stop on the inside of the case. If this was just a little overset (i.e., set at 44 degrees, but you wind the handle a little "vigorously" to achieve a front-of-blade 45 degrees, that may do it. Are you sure that the stop is correctly set? If it is and there's no real effort to swing the blade when reaching the 45 degree position, I don't know what else it could be, apart from wear on the blade carrier rear pivot bolt.

      Ray.
      The problem seems to occur whether I use the stop or if I back-off to say, 40-degrees.

      Comment

      • RayintheUK
        Veteran Member
        • Sep 2003
        • 1792
        • Crowborough, East Sussex, United Kingdom.
        • Ryobi BT3000

        #4
        Originally posted by cgallery
        The problem seems to occur whether I use the stop or if I back-off to say, 40-degrees.
        Weird! I think what I'd do is to remove the winding handle (central Allen-key screw), then the bevel lever (grub screw on the shoulder, which tightens onto a flat face of the subsequent nut - note which face, so you'll know how snug to refit the nut), then the cam actuator, then the nut and two washers.

        This should allow the blade carrier to swing quite freely, so you could determine if there's any slop in the far end of the pivot. If there is, then replace whatever the carrier pivots on - I think it's a bolt, but I'm not absolutely sure.

        Ray.
        Did I offend you? Click here.

        Comment

        • cgallery
          Veteran Member
          • Sep 2004
          • 4503
          • Milwaukee, WI
          • BT3K

          #5
          Originally posted by RayintheUK
          Weird! I think what I'd do is to remove the winding handle (central Allen-key screw), then the bevel lever (grub screw on the shoulder, which tightens onto a flat face of the subsequent nut - note which face, so you'll know how snug to refit the nut), then the cam actuator, then the nut and two washers.

          This should allow the blade carrier to swing quite freely, so you could determine if there's any slop in the far end of the pivot. If there is, then replace whatever the carrier pivots on - I think it's a bolt, but I'm not absolutely sure.

          Ray.
          Okay, got it. This is exactly what I was looking for.

          Comment

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

            #6
            I'm confused.
            Strictly speaking if the blade tilts more in the back than in the fron then the blade is warped which I'm assuming is not really the case.

            What I think I'm hearing is that when tilt the blade you measure the distance from the blade to your SMT referenced dial gauge you're seeing a .01" DIFFERENCE FROM THE reading you get when the blade is 90 degrees.

            Looking at strictly measurement errors, if the blade is tilted then the height at which you measure it is very critical. This then assumes that the height on the blade where you make contact is perfectly the same as on the other end of the blade... if the SMT is tilted oh so slightly then you'll measure a different distance, .01" is quite believable for a very small vertical change of say, about .010" in height!
            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

            • cgallery
              Veteran Member
              • Sep 2004
              • 4503
              • Milwaukee, WI
              • BT3K

              #7
              Originally posted by LCHIEN
              I'm confused.
              That is due to my overwhelming confusion. I just can't get a handle on this.

              First of all, the symptom: I got the saw all set up and everthing was working perfectly. Square cuts no problem w/ the SMT. At the time the blade bevel was set to 90-degrees.

              Then I needed a 45-degree bevel on a cross-cut. I adjusted the blade and made the cut. It looked crooked to my eye. The piece of wood was 3/4" thick and about 4" wide. The cut wasn't square, it was off by 3/32"!

              I thought I had allowed the piece to shift against the fence during the cut. So I tried again, holding it more firmly. Still off. So I used some sandpaper between the fence the board, still off. I know the piece I'm cutting isn't moving relative to the fence.

              So I started examing things and I had initially thought the rear of the blade was deviating about 1/100" when I was tilting it. I've taken another look and I'm not so certain this is the case any more.

              The funny thing is, I experienced these symptoms once before. I got fed up and figured out a different way to finish that project and the next time I needed bevel cuts, it worked fine! Now the problem seems to have returned.

              I tried Ray's suggestion and it swings freely. Doesn't seem to be binding on anything.

              The only thing that seems odd but I can't imagine it causing a problem is that the rear of the blade allows me to pull up on it about 1/32". In doing so, the motor actually travels up a little bit. When I let go, it settles back to where it was. But the travel is on the correct axis and it simply shouldn't contribute to a problem like this. There is no side-side play whatsoever.

              I've tried two different blades, from two different manufacturers, and I just don't get it. The problem is that, due to the nature of table saws, I do believe that what I'm experiencing should be impossible.

              Thanks,
              Phil

              Comment

              • RayintheUK
                Veteran Member
                • Sep 2003
                • 1792
                • Crowborough, East Sussex, United Kingdom.
                • Ryobi BT3000

                #8
                Originally posted by cgallery
                The only thing that seems odd but I can't imagine it causing a problem is that the rear of the blade allows me to pull up on it about 1/32". In doing so, the motor actually travels up a little bit. When I let go, it settles back to where it was. But the travel is on the correct axis and it simply shouldn't contribute to a problem like this. There is no side-side play whatsoever.
                Seems to me that this IS the problem, Phil. If you can "pull up" the rear of the blade, something must have loosened or worn to allow that, surely?

                Even though the "travel is on the correct axis" when the blade is at 90 degrees, if there is wear, then when the tilt is added, perhaps there's a little skew involved somewhere.

                I'm a bit concerned by your "the motor actually travels up a little bit" comment, because I'm sure that must indicate wear or slackness somewhere (shims?)

                When I'm next in the shop, I'll have a pull and poke about inside my saw and see if that sparks off some different thoughts. It won't be until tomorrow, though, as it's 8.21pm now.

                Ray.
                Did I offend you? Click here.

                Comment

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

                  #9
                  Originally posted by cgallery
                  That is due to my overwhelming confusion. I just can't get a handle on this.

                  First of all, the symptom: I got the saw all set up and everthing was working perfectly. Square cuts no problem w/ the SMT. At the time the blade bevel was set to 90-degrees.

                  Then I needed a 45-degree bevel on a cross-cut. I adjusted the blade and made the cut. It looked crooked to my eye. The piece of wood was 3/4" thick and about 4" wide. The cut wasn't square, it was off by 3/32"!

                  I thought I had allowed the piece to shift against the fence during the cut. So I tried again, holding it more firmly. Still off. So I used some sandpaper between the fence the board, still off. I know the piece I'm cutting isn't moving relative to the fence.

                  So I started examing things and I had initially thought the rear of the blade was deviating about 1/100" when I was tilting it. I've taken another look and I'm not so certain this is the case any more.

                  The funny thing is, I experienced these symptoms once before. I got fed up and figured out a different way to finish that project and the next time I needed bevel cuts, it worked fine! Now the problem seems to have returned.

                  I tried Ray's suggestion and it swings freely. Doesn't seem to be binding on anything.

                  The only thing that seems odd but I can't imagine it causing a problem is that the rear of the blade allows me to pull up on it about 1/32". In doing so, the motor actually travels up a little bit. When I let go, it settles back to where it was. But the travel is on the correct axis and it simply shouldn't contribute to a problem like this. There is no side-side play whatsoever.

                  I've tried two different blades, from two different manufacturers, and I just don't get it. The problem is that, due to the nature of table saws, I do believe that what I'm experiencing should be impossible.

                  Thanks,
                  Phil
                  Your numbers are not even consistent.
                  1/100th is .01
                  3/32 is .096 or nearly 1/10th or about 10 times as much.

                  How much is it off? 1/100 or 1/10th?
                  If your cut is off by 1/10th and you measure the blade being off by 1/100th you may have a small problem there but that not the major problem.

                  Barking up the wrong tree?

                  it would not surprise me that you can lift the blade and motor assy 1/32 by pulling the blade up. That's probably backlash in the elevation mechanism. Gravity tends to keep that from showing up, mostly.
                  Last edited by LCHIEN; 09-14-2006, 02:28 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

                  • cgallery
                    Veteran Member
                    • Sep 2004
                    • 4503
                    • Milwaukee, WI
                    • BT3K

                    #10
                    Originally posted by LCHIEN
                    Your numbers are not even consistent.
                    1/100th is .01
                    3/32 is .096 or nearly 1/10th or about 10 times as much.

                    How much is it off? 1/100 or 1/10th?
                    If your cut is off by 1/10th and you measure the blade being off by 1/100th you may have a small problem there but that not the major problem.

                    Barking up the wrong tree?

                    it would not surprise me that you can lift the blade and motor assy 1/32 by pulling the blade up. That's probably backlash in the elevation mechanism. Gravity tends to keep that from showing up, mostly.
                    The first number, 1/100th, is how much I thought the blade was off. 3/32" is how much the cuts were off. I thought the small error in the blade was causing the blade to pull the stock relative to the fence and introducing a larger error. I was grasping at straws!

                    However, I have found the culprit. And I'd rather die than admit the problem.

                    The two scrap pieces I've been cutting for test purposes, are of uneven thickness from one edge to another. I went home and instead of looking at the saw I looked at the wood and discovered that BOTH pieces were thicker on one edge than the other!

                    LESSON LEARNED: When checking squareness of bevel cuts with a combination square, checking the bottom (shorter length) tells you if your cut is square. Checking the top (longer length) tells you if your stock is of uniform thickness.

                    Sorry everyone for the confusion. I'm going to go throw up.

                    -Phil
                    Last edited by cgallery; 09-14-2006, 02:47 PM.

                    Comment

                    • JR
                      The Full Monte
                      • Feb 2004
                      • 5633
                      • Eugene, OR
                      • BT3000

                      #11
                      Originally posted by cgallery
                      ... I'm going to go throw up.
                      I'd go ahead and blame it on the bulemia. Maybe that's just me.

                      JR
                      JR

                      Comment

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

                        #12
                        well, I'm glad you found it.
                        My point was that the error in squareness of the wood has to be less than the error you thought you measured in the blade from one end to the other if the piece of wood is less wide than the blade at that point.

                        So you were barking up the wrong tree.
                        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

                        • cgallery
                          Veteran Member
                          • Sep 2004
                          • 4503
                          • Milwaukee, WI
                          • BT3K

                          #13
                          Originally posted by LCHIEN
                          well, I'm glad you found it.
                          My point was that the error in squareness of the wood has to be less than the error you thought you measured in the blade from one end to the other if the piece of wood is less wide than the blade at that point.

                          So you were barking up the wrong tree.
                          I got your point. I was subscribing to the CTW (Chaos Theory of Woodworking) at the time. That is, insignificant occurences elsewhere were causing a chain of events that culminated in giant errors in the squareness of my bevels. You were right, but I had become nonlinear.

                          I've gotta admit that I totally went on a rip on this one. I'm not proud of my behavior. The other lesson I learned was to avoid trying solutions until I fully understand the problem. Problem is, I've learned this lesson about sixteen hundred times and I keep forgetting it. :-)
                          Last edited by cgallery; 09-14-2006, 03:30 PM.

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