Panels not coming out square

Collapse
This topic is closed.
X
X
 
  • Time
  • Show
Clear All
new posts
  • sailor55330
    Established Member
    • Jan 2010
    • 494

    Panels not coming out square

    I'm working on a project that involves cutting 2 side pieces out of 1/2" maple ply. The dimensions are 11.5 wide by 31 high. This will be framed by 3/4 maple stock to form a shadowbox. The ply will be back/bottom. I really thought I had my saw set up correctly, but apparently I don't. My 2 sides have come out slightly out of square. When I check diagonals, I am about 1/32" off. I think this is due to the cross cut sled. I've checked it and it seems to be in square with the blade/miter slots.

    I've tried the 5 cut method, but I'm doing something wrong as I usually end up with over 1/2" variance across a 12" panel.

    How crazy should I drive myself over 1/32" over a 31" diagonal?

    Thanks for the patience.
  • leehljp
    Just me
    • Dec 2002
    • 8429
    • Tunica, MS
    • BT3000/3100

    #2
    Sailor,
    For people here that are experienced, I don't challenge their techniques, but "assume" that the problem is not technique. I don't challenge your technique either, but mention a habit that we sometimes get into without realizing: When I (and I have seen others do this) want something perfect, our feed is purposefully held firmly. An overly firm hold in the feed will distort the flow that much.

    Purposefully pushing a long rip "firmly against the rip fence" instead of "focusing on feeding the longboard straight forward" often forces a slight distortion in the cut. This happens more than one would think.

    I tend to get the distortion you mentioned from the above from my technique more than saw settings. Not saying this is your problem, but rather just mentioning it.
    Last edited by leehljp; 01-30-2016, 09:10 PM.
    Hank Lee

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

    Comment

    • mpc
      Senior Member
      • Feb 2005
      • 979
      • Cypress, CA, USA.
      • BT3000 orig 13amp model

      #3
      Are you having to move the saw between cuts? Many folks have space challenged shops and have to move the saws to make wide crosscuts for example. If the shop floor is uneven the whole BT3 saw body and leg assembly could be twisting ever so slightly, enough to throw things off.

      Another thing that gets folks from time to time, especially doing things like making tenons on a table saw, is a rip fence that is not 90 degrees vertically relative to the table surface. Thus, when the workpiece is flat to the table, the end of the tenon is against the bottom of the rip fence. Rotate the workpiece 90 degrees to make the next cuts on the tenon and now the tenon rides along more of the fence surface. If the fence is not 90 degrees to the tabletop - such that the top of the fence is a tad closer to the blade than the bottom - those tenon cuts will be a teensy bit shorter than the first cuts. The shoulder of the tenon will thus be uneven on the 4 sides of the tenon. Depending on how/what technique you use to check if your fence is aligned to the blade this could mask a fence issue. I use simple plastic drafting triangles to check a lot of stuff. They're pretty thin so they reference off the bottom of the rip fence and bottom of the miter fence. If either fence isn't perfectly perpendicular to the tabletop, normal thickness workpieces will be affected.

      I've also experienced what Hank described. It's easy to shove the workpiece hard into the rip fence at the start of the cut but it's almost impossible to maintain that lateral force once more of the workpiece is in contact with the fence and especially when the cut is nearly complete - you'd be pushing the offcut into the blade. That results in a cut line not perfectly straight - almost like you took a hand plane or sandpaper to part of the edge of the workpiece near the starting corner.

      mpc

      Comment

      • radhak
        Veteran Member
        • Apr 2006
        • 3058
        • Miramar, FL
        • Right Tilt 3HP Unisaw

        #4
        Personally, I think of 1/32", particularly along the diagonal, as 'margin of error'.

        IOW - I would think of it as close enough as to not matter.
        It is the mark of an educated mind to be able to entertain a thought without accepting it.
        - Aristotle

        Comment

        • cwsmith
          Veteran Member
          • Dec 2005
          • 2737
          • NY Southern Tier, USA.
          • BT3100-1

          #5
          A 32nd of an INCH... If you were machining steel I'd say you have a serious problem. But for wood and a table saw, my humble opinion would be that it's just about perfect.

          So many variations to be dealt with even with a BT3. Even if you breath the wrong way you could be off that much. Question is, whether you are consistently getting that variation. If it was consistent, then I might think that your procedure is perfect and that some ever-slight adjustment could be made. But really, for wood working that little variation over a 31" length might be considered quite reasonable and that you are exceptionably skilled. (I've known draftsmen that couldn't draw a line that skillfully, either straight or in width.)

          There are of course perfectionists, I wish that I could have the tools and the skills to be one,

          CWS
          Think it Through Before You Do!

          Comment

          • sailor55330
            Established Member
            • Jan 2010
            • 494

            #6
            Thanks to all who have provided insight. I would say there is a good chance that I applied a little extra effort against the rip fence. I guess too many Youtube videos will put some scare into your actions. Plus, since I was trying to make this piece as nice as I can, I probably tried a little too hard. As I mentioned, the panels are 1/32 of an inch off on the diagonals, yet, when I hold a square against the edges, it's pretty significant. Across the 11.5" width, I guess that the square rises a little more that 1/16. This panel will have a 3/4 frame around it in a shadow box style, so, the gap becomes pretty noticeable (and I am one of those who can't stand for these type of things to be off). I do have 2 panels that have pretty close to the same variation. The tools are not bad, but certainly not pro quality and the technique is certainly far from perfect, or great, or maybe even good, but the eye and brain won't let that be an excuse.

            Any suggestions short of re-cutting the panel? I can pull the frame to the panel and close the gap with clamps, but over time, I think that wouldn't be the best idea.

            Thank you again for all the advice.

            Comment

            • poolhound
              Veteran Member
              • Mar 2006
              • 3195
              • Phoenix, AZ
              • BT3100

              #7
              I am never a fan of closing gaps with clamps although yes I have done that myself :-( It typically has other undesirable knock on effects. Only this week I was making a new DP stand and I must have cut the shelf slightly too narrow. The joint was held with glue and brads and a little 'extra' clamping to hold things square. When I came to fit the drawers there was a measurable bow in the sides and the dang drawers didnt fit! The sounds of gnashing teeth and expletives filled my shop and it caused me at least an hour or so to fix things.

              If I understand your project correctly and assuming you are now confident about cutting the panels square I would just trim them square and adjust the final dimensions of the project slightly. You had said there was a frame to go around the edge, could this be made slight larger to accommodate?


              Originally posted by sailor55330
              Thanks to all who have provided insight. I would say there is a good chance that I applied a little extra effort against the rip fence. I guess too many Youtube videos will put some scare into your actions. Plus, since I was trying to make this piece as nice as I can, I probably tried a little too hard. As I mentioned, the panels are 1/32 of an inch off on the diagonals, yet, when I hold a square against the edges, it's pretty significant. Across the 11.5" width, I guess that the square rises a little more that 1/16. This panel will have a 3/4 frame around it in a shadow box style, so, the gap becomes pretty noticeable (and I am one of those who can't stand for these type of things to be off). I do have 2 panels that have pretty close to the same variation. The tools are not bad, but certainly not pro quality and the technique is certainly far from perfect, or great, or maybe even good, but the eye and brain won't let that be an excuse.

              Any suggestions short of re-cutting the panel? I can pull the frame to the panel and close the gap with clamps, but over time, I think that wouldn't be the best idea.

              Thank you again for all the advice.
              Jon

              Phoenix AZ - It's a dry heat
              ________________________________

              We all make mistakes and I should know I've made enough of them
              techzibits.com

              Comment

              • cwsmith
                Veteran Member
                • Dec 2005
                • 2737
                • NY Southern Tier, USA.
                • BT3100-1

                #8
                Sailor,

                I understand your quest for perfection. How accurate is your square? Framing squares are notoriously off. The last time I bought one, I went through every 'Empire' framing square that Home Depot had (over a dozen) and didn't find one even close to accurate. I went to Lowes and found the same inaccuracies with theirs. Finally I did find one decent Stanley at the local Home Value store.

                For in shop use, I have several drafting triangles and a couple of Theo. Alteneder & Sons stainless steel triangles, which are a bloody fortune. None of them though have a reach of more than twelve inches... good for checking the tools and for short lengths.

                Again, 1/32 over 31" doesn't sound like a particularly big deal, but I do understand your quest for perfection; and, thinking that in the course of an eight-foot cut, you'd still be less than an 1/8 th inch. That would probably bother me if I was building a piece of furniture.

                CWS
                Last edited by cwsmith; 02-01-2016, 07:49 PM.
                Think it Through Before You Do!

                Comment

                • capncarl
                  Veteran Member
                  • Jan 2007
                  • 3564
                  • Leesburg Georgia USA
                  • SawStop CTS

                  #9
                  I understand your panels not being square but A lot of time your cuts are not off, it will be off because of a twist in the board that shows up at the last cut. That is just the tree going back to the shape it was in the woods. I see this all the time when cutting down a really nice flat and square 2x6 into smaller pieces. Some of the slices from this board will almost walk off. Clamps are your friends.

                  Comment

                  • trungdok
                    Established Member
                    • Oct 2012
                    • 235
                    • MA

                    #10
                    I agree with capncarl, your board might not be flat. Still that's not a big deal as you won't see it once all assembled. Honestly, I wouldn't worry about it.

                    Also, 1/32" off diagonally should give you 1/64" off (at max) when checking with the square on the shorter side. If you are seeing 1/16" off, then check your square.

                    Comment

                    • cwsmith
                      Veteran Member
                      • Dec 2005
                      • 2737
                      • NY Southern Tier, USA.
                      • BT3100-1

                      #11
                      Off 1/32" DIAGONALLY! I do believe that I missed that "diagonally" part, and have been thinking that your dimension was horizontally the difference in the cut at the end of 31".

                      What can I say, poor reading comprehenson... actually, too much of in a rush. But as trungdok pointed out that's nothing to "worry about".

                      Actually I would consider that pretty incredible, so I guess I admire your quest for precision wood working. Personally, I think that if you breathed on the wood, you'd probably cause a swelling that would be off at least that month. I just took a look at my 12-inch engineers scale and I'm wondering how you even measured that difference with repeated accuracy unless you're using a pretty large vernier caliper.

                      CWS
                      Last edited by cwsmith; 02-03-2016, 07:18 PM.
                      Think it Through Before You Do!

                      Comment

                      • capncarl
                        Veteran Member
                        • Jan 2007
                        • 3564
                        • Leesburg Georgia USA
                        • SawStop CTS

                        #12
                        Most of the woodworking tools used by the folks on this site are not really capable of hitting that kind of close tolerances without a great deal of fiddling with fences and jigs. The bt3 saw, like most all hobby saws, does not have a long enough sliding miter gauge or rip fence to maintain accuracy on big pieces. To cut a 30" panel accurately you should have 30" rip fence or sliding tale in front of the blade and that much behind the blade, less your inadvertently twist the panel a wee bit while pushing it past the blade. This much saw realestate is only found on high end saws. My Powermatic saw rip fence only has about 16" of fence before and after the blade and I often catch myself giving the wood that last little push as it completes the cut and the piece leaves the fence and does a little twist and knocks the cut out of square.
                        capncarl

                        Comment

                        • sailor55330
                          Established Member
                          • Jan 2010
                          • 494

                          #13
                          Thanks again to all that offered advice on this. I'm still not 100% sure where I was off, but I now have the panels square. I think it was a combination of things:

                          1. The square I was using may not have been totally accurate. I did try to test it by drawing a line and then flipping the square. It was ever so slightly out. I was able to "peen" it into a tolerance that a .5MM pencil lead could mask.
                          2. I broke down and ordered some drafting triangles to confirm my sled was square---it is. This also helped me realize that I was very close to square anyway--closer than I had thought
                          3. I trimmed the panels every so slightly-----probably 1/32 or so I'm guessing. Given that this is a shadowbox that hinges on the outside of the armoire, my guess is no one will know if I shorten the length by 1/32-1/16 if I don't tell them.
                          4. I realized I didn't chamfer the bottem edge of my straight edge on my saw sled, which could easily have led to a small piece of debris causing an unsquare cut.
                          5. Last and most important, my technique probably leaves a lot to be desired.

                          Bottom line is the project can now move forward thanks to the suggestions and knowledge here. Thank you all.

                          Comment

                          Working...