smt alignment

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  • siliconbauhaus
    Senior Member
    • Dec 2006
    • 925
    • hagerstown, md
    #1

    smt alignment

    I just did the 5 sided test on a piece of mdf that was about 225 square. I ended up with a piece that was 211 long and out by 1mm over the length.

    Am I correct in thinking that this means I'm out 1mm over approx 800mm and is that acceptable?

    Sorry for the metric but I had a mm machinists scale at the time.
    パトリック
    daiku woodworking
    ^deshi^
    neoshed
    Tags: None
    • cgallery
      Veteran Member
      • Sep 2004
      • 4503
      • Milwaukee, WI
      • BT3K
      #2
      Converting to imperial: You're a little more than 1/32" off over roughly 31.5 inches.

      But, I don't trust the five cut method. I've yet to get repeatable results, or see any of my friends that are proponents get repeatable results. Too many opportunities to screw-up. The piece could slip during a cut. Or the blade could deflect a little. Or sawdust could get between the piece and the fence on one cut.

      I use my Starrett square to check pieces that are 12" or narrower. I seldom need wider than that, but I do have a large carpenters square that I've tested and found to be accurate enough for work of that scale.

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        • siliconbauhaus
          Senior Member
          • Dec 2006
          • 925
          • hagerstown, md
          #3
          Hmmm yeah you're probably right mate.

          I'm going to borrow my Dad's dial indicator and starrett square and try again. Would I be going in the right direction by zeroing the indicator against the blade from the front and then sliding the smt to the back?
          パトリック
          daiku woodworking
          ^deshi^
          neoshed

            Comment

            • crokett
              The Full Monte
              • Jan 2003
              • 10627
              • Mebane, NC, USA.
              • Ryobi BT3000
              #4
              I'm with cgallery - I use a square to check for square, ever since the cut method said something was not square but 3 of my squares said it was.
              David

              The chief cause of failure in this life is giving up what you want most for what you want at the moment.

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                • LCHIEN
                  Super Moderator
                  • Dec 2002
                  • 21732
                  • Katy, TX, USA.
                  • BT3000 vintage 1999
                  #5
                  Originally posted by siliconbauhaus
                  Hmmm yeah you're probably right mate.

                  I'm going to borrow my Dad's dial indicator and starrett square and try again. Would I be going in the right direction by zeroing the indicator against the blade from the front and then sliding the smt to the back?
                  Seems like you're going about this in apple and orange fashion.

                  The 5-cut deal I believe involves using the Miter fence and rotating the piece each cut. The amount you're out of square at the end is a function of how closely you have the miter fence to Square (90° to the blade).

                  The next method you propose measures an entirely different thing. Using a dial gauge mounted to the SMT and measuring the distance to a front tooth and then a back tooth only can ensure that the SMT Slides precisely parallel to the blade. That has an entirely different effect than having the miter fence at 90° to the blade.

                  In reality you need to set both miter fence at 90 and SMT parallel to the blade as part of a tune up but one test is not a substitute for the other.
                  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

                    • LarryG
                      The Full Monte
                      • May 2004
                      • 6693
                      • Off The Back
                      • Powermatic PM2000, BT3100-1
                      #6
                      I'm not familiar with the five-cut test, but there's a simpler way to check crosscuts for accuracy. This works for any table saw, not just the BT types:

                      Get a scrap of plywood, MDF, whatever, that's about a foot square. The exact size of the piece doesn't matter except that it must be within the crosscut capacity of your saw: the larger, the better.

                      Select the truest edge and place this against the SMT fence or miter gauge. Make a crosscut to remove a small section from the test piece's right side (i.e., nearest the blade). A 1/4" offcut is plenty.

                      Flip the test piece side-for-side, keeping the same reference edge against the SMT fence or miter gauge, and make a second crosscut to remove another small section from the side that is now nearest the blade.

                      Measure both ends of the test piece; i.e., along the reference edge that was against the SMT fence or miter gauge, and at the end opposite. If the two measurements are not exactly equal, your saw is not cutting squarely.
                      Larry

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                        • cabinetman
                          Gone but not Forgotten RIP
                          • Jun 2006
                          • 15216
                          • So. Florida
                          • Delta
                          #7
                          I think crokett said it best in another thread that there are 18 ways + Sunday. My test is like some others here, pretty simple. I use a framing square, or try-square, or a combo square (which BTW you can buy with an 18" blade).
                          .

                            Comment

                            • siliconbauhaus
                              Senior Member
                              • Dec 2006
                              • 925
                              • hagerstown, md
                              #8
                              I'd use the square to align the fence and then use the dial indicator to makes sure I'm parallel.

                              I tried using a framing square but it had imperial on one side and metric on the other so it just complicated things.

                              Maybe I'm being a bit anal about the accuracy but I'd rather spend some time now and have it as accurate as possible. I think eventually I'm going to go with a mitre slot on both sides of the blade and build a sled.
                              パトリック
                              daiku woodworking
                              ^deshi^
                              neoshed

                                Comment

                                • pecker
                                  Established Member
                                  • Jun 2003
                                  • 388
                                  • .
                                  #9
                                  I have had good luck using a large drafting square. Big ones are only $7 or so.
                                  Just crosscut a wide piece of mdf...say 12" wide. Leave it on the smt, against the miter fence. Then set the drafting square on top of the mdf, and it's easy to see how far off you are from square. I wasn't happy until I had it adjusted to less than .01" over a 12" distance. But you may have looser, or tighter requirements yourself.
                                  http://www.draftingsteals.com/catalo...triangles.html

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