45 degree miter joint jig-sled for BT3x using SMT

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  • 45 degree miter joint jig-sled for BT3x using SMT

    As I mentioned elsewhere I have decided to make a 45 degree miter jig for my BT3 somewhat along the principles of this Rockler miter slot sled Jig.
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    The idea is that it is easier to make a perfect 90 degree corner than a 45. Errors in a 45 will accumulate 8 times around a picture frame so a 0.12 error in each cut on a miter saw will result in a 1 error on the finished frame. 0.12 is hard to see but 1 degree is pretty obvious in the finished work.

    If you get a perfect 90 and cut the two joined pieces on the complementary sides then the errors in 45 will cancel out because the joint will always add up to 90 degrees, i.e. the errors cancel out so that 45.1 + 44.9 = 90 degrees. And all four corners will be square.

    First thing I needed was a near perfect 90 degree square corner. I have built these right angle assembly squares, So I checked them for square (still right on to my protractor and all my Try squares) so I used my existing squares to square up and glue the new one (middle of the sandwich) and checked it, after the glue set I put some deep screws into it for long lasting strength:

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    Now you may ask why a butt joint (ugh, right) and why didn't I use mitered corners or other various jointer like half laps etc. I needed most of all perfectly square; strength is secondary, so simple leads to the fewest errors. This wood was planed and edge jointed and cut as square as I could. Glued between a pair of good assembly squares I then put 3" screws into the butt joint to hold it.

    Hints as to the further plans:

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    Attached Files
    Last edited by LCHIEN; 03-08-2022, 08:45 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

  • #2
    The key to my thinking is, this will have a base plate that mounts to the SMT. Then the Assembly square I made has to be attached to the base plate and extend almost to the blade. It needs to be at the proper angle to the blade, assuming that the SMT is properly adjusted to slide parallel to the blade.
    Just in case, the assembly square fence has to be mounted at roughly 45 degrees with about 1 or 2 degrees of adjustment so the arms of the square fence can be adjusted to 45/45 with the blade. It doesn't need to be perfect but in my view it should be adjustable for various factors. This requires a separate mounting bracket.

    So, I cut the mounting bracket for the square fence that would turn it 45, then I hot melt glued it to the baseplate.
    I drilled a 1/8" pilot hole aligned thru both pieces at three places - one of which will be the pivot and the other two adjusting points.
    Then I pried it apart and scraped off the glue.

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    I then put three fixed 1/4-20 T-nuts in the base bottom, countersunk slightly to recess them and then a 5/16th hole for the body.
    In the mounting bracket I drilled a 1/4" hole for the single pivot on the end and then a little over 3/8" hole for the two on the side. This gives me about 1-2 degrees of adjustment. It may not be obvious but the bracket is set about 1/8" past the end of the baseplate to give it room to move when adjusted.


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    For my final trick of the night I glued the bracket to the square fence. The combined height of the baseplate plus the bracket is 1.5", same as the thickness of the square fence. But I glued the baseplate about 1/16th proud (below) of the square so as the SMT slides the square fence will not drag on the main table. I hope that was a good idea. You can see the mounting bracket on top is 1/16th below the square fence. And the bottom view showing the T-nuts, you can see the 1/8th inch I left between the baseplate and the square fence. Tomorrow I when I work on it and the glue has set I will put a couple of screws through the bracket into the square fence to hold it. backing up the glue. I already drilled the angled holes in the bracket you can just see them and the pencil mark showing the hole path.

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    For my next trick, hopefully tomorrow, I will show you how I mount this sucker to the SMT.
    Attached Files
    Last edited by LCHIEN; 03-11-2022, 11:49 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


    • #3
      I want to use the two miter fence pivot holes on either side of the SMT to repeatably mount the sled to the SMT. The two pivot holes are just a hair over 3/8" so a 3/8" dowel slips in easily but with not much play. I determined approx where I wanted the sled, right to left.
      The pivot holes appeared to be 9-5/8" apart, but I wanted a more accurate determination.
      I placed one hole 1/2 inch from the lower edge of the 1x4 base.for the left side and put in a dowel.
      I then used a dowel center in the right hole, set the base on the left hole and marked the right side by swinging a small arc and scratching the bottom with the dowel center, then marked 1/2" up and drilled that intersection.

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      Next I determined the slot location for a 5/16-18 hex head bolt and knob to hold the base down, like the miter fence is usually held.

      I drilled a 3/8" hole the width of the intended slot halfway in the base. Raised the blade to the center of the hole, and then used the miter fence on the SMT to nibble away the slot. The bolt head drops in the large hole at the end of the slot in the SMT and then you slide the bolt to the center of the base and tighten the knob. I use a flat washer under the knob and on top of the base.
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      Bottom view of the base and bracket:

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      I mounted the bracket and square fence. This short video shows the adjustment range it has, P3090894.AVI

      I used a drafting triangle to set the 45 degree relative to the blade, then tightened the two bolts left and finally the pivot bolt in the right center to hold it.

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      Quick slide check: P3090898.AVI

      Quick cut check: P3090902.AVI

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      It was late! Called it a day.

      Looks like a big detour sign, now that I look at it.
      Attached Files
      Last edited by LCHIEN; 03-22-2022, 02:45 AM.
      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


      • #4
        This is incredible, and very relevant to some work I am trying to complete! I'll have to give creating my own a whirl. Thank you for the (constant) inspiration

        Comment


        • #5
          Interesting jig. Very useful particularly if you don't have a miter saw. Could be VERY useful for someone looking to downsize their shop and squeeze as much function out of their BT3x00 as possible. Great work!
          Please like and subscribe to my YouTube channel. Please check out and subscribe to my Workshop Blog.

          Comment


          • furthermore
            furthermore commented
            Editing a comment
            I have a miter saw but cutting complementary angles like Loring describes is still difficult and error prone, even with a nice one with 45 degree detents. This method is similar to what Tage Frid describes for cutting complementary angles (his sled uses miter slots but we don't have those)

          • LCHIEN
            LCHIEN commented
            Editing a comment
            Furthermore - exactly!

        • #6
          Rather than make it adjustable, and have the ability to get all out of kilter, why not make it fixed and also make a 45 set up jig that fits over the raised blade and you adjust the 45 miter jig to that blade jig. You only have to adjust the attachment to the sliding table and not touch your 45s at all.

          Comment


          • #7
            Originally posted by capncarl View Post
            Rather than make it adjustable, and have the ability to get all out of kilter, why not make it fixed and also make a 45 set up jig that fits over the raised blade and you adjust the 45 miter jig to that blade jig. You only have to adjust the attachment to the sliding table and not touch your 45s at all.
            The 90 degree square fence is fixed as that is the basis of making complementary angles.
            The 45 degrees is adjustable to the blade, exactly as I think you suggest. This makes
            • the pair of angles is fixed and perfectly complementary and add up to 90.0 as closely as possible
            • the 45 to the blade is adjustable to make the pair of angles close to equal as this is secondary to the complementary pair equaling 90. In other words if the fence is precisely 90, setting one side of the fence to 45 to the blade makes the other side precisely 45 as well.
            With three bolts locking the adjusted angle its not going to go out of kilter unless you adjust your SMT. Adjusting the SMT does not make the complementary pair =90 go out of kilter, ever.
            Last edited by LCHIEN; 03-12-2022, 01:27 AM.
            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


            • #8
              Very nicely done! Now don't forget to stain and varnish it.
              Jim Frye
              The Nut in the Cellar.
              ”Sawdust Is Man Glitter”

              Comment


              • #9
                Originally posted by dbhost View Post
                Interesting jig. Very useful particularly if you don't have a miter saw. Could be VERY useful for someone looking to downsize their shop and squeeze as much function out of their BT3x00 as possible. Great work!
                Dave, I have a miter saw but the purpose of this is to make more accurate 90 degree corners using 45 miters that are complementary to 90 degrees instead of trusting that the miter saw detent is exactly 45 but actually 45.1 or 45.2 resulting in 90.2 or 90.4 degree corners that continue to build going around a rectangular frame. It at least saves the setup time, hopefully. especially if going back and forth cutting one end and the other to make the miter saw precisely 45 each time. On this sled you have both set up simultaneously and don't have to change anything between cuts.

                Loring
                Last edited by LCHIEN; 03-09-2022, 08:44 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


                • dbhost

                  dbhost
                  commented
                  Editing a comment
                  No doubt. Actually a series of these jigs with the common angles would make miter saw almost moot. Given shops with space issues it really isn't a bad idea... I've not given up on the idea of a stand alone shop considering my wifes proclivity toward storing stuff that isn't shop stuff in my garage workshop...

                • LCHIEN
                  LCHIEN commented
                  Editing a comment
                  Dave, again other angles don't give the advantage. 90 degree fence is easiest to make in that all our squares and stuff are precise and readily available the in-between angles are harder to DIY make with assured accuracy.

                • capncarl
                  capncarl commented
                  Editing a comment
                  A miter saw is a must for a small start up shop! If you are doing 45 degree frames the miter saw works exactly like this jig! If you don’t move the angle on the miter saw, leave it setting on 45 you can cut both sides of the 45, remember they are still complementary angles! The hardest part of any of these operations is cutting each leg the correct length, if just one leg is just a smiggen too long it throws everything off!

              • #10
                There a few things left to do.
                JIm Frye suggests staining or varnishing... I haven't been too good doing that to my jigs. Not a big fan of finishing. Maybe.

                I want a tall push handle. Either replace the knob with this which should fit or perhaps put it closer to the blade (lik3 on the bracket) so its easier to push near the cutting point instead of off-center. Amazon has one similar but its $15 for 2. Rockler is 45 minutes away in heavy traffic. I will get one next week when I visit my son in Austin and the Austin area Rockler is less than 5 minutes away from his house.
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                The other thing that may be solved by the handle and maybe not is holding the workpieces. The first cut is pushed but with a 45 degree angle so it wants to slide off the fence a bit. Same as with a conventional miter on a miter fence cut on a TS which is an advantage of a Miter saw. The second cut is worse, not only because the 45 but also because the blade is pulling the workpiece away from the fence. Not only that but trying to hold the workpiece firmly to the fence puts my hands uncomfortable close to the fence considering I can't span the workpiece and fence easily.

                I am seriously thinking about drilling some large diameter holes in the fence so I can put a small F-clamp or a Rockler fence clamp to hold the workpiece to the fence in both cuts. I think some experimentation is necessary. I'm worried that fence attached clamps may risk hitting the blade.

                Because of these concerns I have still yet to make a full frame using this jig.

                My last thought is perhaps I should have set the nose of the fence right against the blade. You will notice that I set the nose position of the sled about 1/4 inch from the blade and that I beveled just a small bit off the nose. By setting the nose against the blade it gives a positive indication of where the cut will be made on the workpiece. Something I don't have right now. If you notice I have always kept a spacer between the main table and the SMT. And while it just sits there it keeps me from moving the SMT closer to the blade to touch. I can move the SMT farther away easier but the easier way to move it closer is to move the pegs and slot which is not easy.

                So we're not quite done yet.
                Last edited by LCHIEN; 03-09-2022, 08:49 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


                • #11
                  Thinking about this arrangement of holes permitting the workpiece to be clamped to the square miter fence. Bigger holes for 4" Bessey F clamps (shown) and the smaller hole will work for Rockler Fence Clamps. Going to have to be careful not to cut the clamp! But I feel better about that than sticking the fingers over the workpiece to hold it.

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                  First test cut but I was concerned about my ability to hold the short piece to the lower side fence, wanted to come off the fence - doesn't take much to open up the angle. Will need to redo this test when I get the workpiece clamping.

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                  Looking at an ideal location for the push handle gives me another idea. Replace the Pivot bolt in the bracket with a 1/4-20 hanger bolt; and thread the wood screw part into a 1.25" dia. dowel about 3-3/4 inches long.

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                  Last edited by LCHIEN; 03-10-2022, 02:29 AM.
                  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


                  • #12
                    OK, I implemented some of the things I was thinking about.

                    I made my own handle instead of buying the $7 one from Rockler or the $15 for 2 from Amazon. I used a 1/4"-20 x 3 hanger bolt (2 for $1.28. Lowes curbside, he brought it to my car)
                    I think the handle location is perfect now. A piece of 1-1/4" dia x 4" dowel was used.

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                    And I drilled holes in the fence to enable clamping the workpiece to the fence:

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                    I guess I need to do some miters to test this out.
                    Attached Files
                    Last edited by LCHIEN; 05-08-2022, 02:06 AM.
                    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


                    • #13
                      Shall I trim off tbe left side of the base overhanging tbe SMT? Not doing anything useful but makes it look better balanced. Maybe put a hanging hole in it. Then it will look like an arrow pointing to heck.
                      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


                      • capncarl
                        capncarl commented
                        Editing a comment
                        I would rather see a couple of captive slats that hang off both side of the sliding miter table to prevent any doubt of movement!

                      • LCHIEN
                        LCHIEN commented
                        Editing a comment
                        capncarl, there are two pegs 10" apart that fit closely into the two holes used for the BT3 miter fence pivots. The knob just locks it. The baseplate is not going anywhere and the alignment is identical every time its mounted, relative to the SMT. Look back at the pictures of the baseplate. https://www.sawdustzone.org/filedata...970&type=small
                        Last edited by LCHIEN; 03-22-2022, 03:04 AM.

                    • #14
                      Nice jig.

                      With respect, I don't like seeing the clamp handles in the cut line. Sure, I make stopped cuts on the table saw. ... but ... I would never arrange a cut setup with an obstruction in the cut line like that. I am not judging others and their work methods. Such a cut can be safely done. I am merely saying what I would and would not do.

                      Comment


                      • #15
                        Originally posted by duramen View Post
                        Nice jig.

                        With respect, I don't like seeing the clamp handles in the cut line. Sure, I make stopped cuts on the table saw. ... but ... I would never arrange a cut setup with an obstruction in the cut line like that. I am not judging others and their work methods. Such a cut can be safely done. I am merely saying what I would and would not do.
                        Yeah it disturbs me, too. But the SMT is physically stopped by my outfeed table.
                        I'm more worried about clamping items on the other side where the clamp gets to the blade before the workpiece. The front side clamp is less necessary as the blade naturally wants to push the wood towards the fence.


                        But I'm a lot happier with the clamp on the backside of the fence even if there is a risk of cutting the handle. Compared to trying to hold the workpiece to the backside where the blade wants to rip it away from the fence and risk making a less than perfect miter as well as the thrown part danger.
                        Last edited by LCHIEN; 03-11-2022, 02:52 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

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