Making My Own Miter Slot

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  • Making My Own Miter Slot

    I am a new owner and a long ways from making a miter slot, but I am thinking about. When I looked at the designs and the articles that I have read here and elsewhere, I wonder if there is a simple way of making a simpler miter slot.

    Two things strike me as I look at the saw, and the other saws I have seen. Do these simplifications make sense?


    1) Miter slots on other are almost always fixed - there is little need to move them along the fence rails - they may need to be removable, but they really don't need to slide. The only thing that is necessary is that the base that contains the miter slot be able to be reliably replaced every time I put it in - it doesn't need to be parallel to the blade, as long as I put it back in the same way every time.

    2) People seem to want to cut the miter slot first, and then adjust the base of the miter slot - why not do it the other way? If I follow #1, and develop a method for placing the base in the same place every time, then why not use the rip fence (which has been carefully adjusted to be parallel to the blade) as a guide for the router?

    This leads me to think of building a miter slot the following way:

    1) Use a piece of MDF (or something else that is pretty stable). Slide the left edge of it against the right side of the center portion of the saw. There may need to be some T-nuts to hold it in place, but they are not needed to make sure it's parallel.

    If the left edge of the MDF "base" isn't stable enough, route a little rabbit in the edge of the MDF, and screw/epoxy a piece of angle iron to the edge of the base - the point again being that the base doesn't have to the parallel to the blade - you just need to be able to put it in the same place every time.

    2) Put the piece of MDF in place.

    3) Adjust the table saw fence so that when a router is held against it, a router bit will be more or less in the center of the the MDF.

    4) Run the router along the saw table fence to cut the miter slot. If the fence is parallel to the blade, then the miter slot will be parallel to the blade.

    Is the weak point in this design:

    1) It's very hard to get the base in the same position every time, even if it doesn't need to be parallel to the base?

    2) I am too optimistic about the parllelism of the rip fence and the blade?

    Just thinking,

    Mike

  • #2
    Read this article by Rod Kirby and his version of a miter slot:

    https://www.sawdustzone.org/articles...for-the-bt3000
    No good deed goes unpunished

    Comment


    • #3
      quote:Originally posted by Hoover

      Read this article by Rod Kirby and his version of a miter slot:

      https://www.sawdustzone.org/articles...for-the-bt3000
      That article was what got me thinking. If I understand what that article did was

      1) Route the miter slot
      2) Adjust the miter "base" so that the slot was parallel to the blade

      What I am proposing

      1) Add the miter base - it's position doesn't matter (as long as you can put in the same location each time)

      2) Route the miter slot using the rip fence.


      Thanks,

      Mike P. Wagner

      Comment


      • #4
        Maybe I didn't understand correctly, but the miter slot itself DOES need to be parallel to the blade.

        Regards,
        Tom

        Comment


        • #5
          Hi Tom:

          I follow what Mike's saying. He agrees with you that the miter slot needs to be parallel to the blade. But his question is why go to all the trouble to make the slot parallel to the edges of the miter slot table (MST), and then worry about parallelism again when mounting the MST to the saw?

          He's looking for fatal flaws with the idea of mounting a solid, unmilled piece of MDF to the right of the blade and then making the miter slot after it's intalled, using the rip fence to guide a router. His way, he's only worrying about parallelism once; after the MST is already installed.

          Mike: I think the primary appeal of your idea is that the rip fence is a very convenient way of guiding the router.

          But there are two risks to your method. The first risk is the rip fence only guides the router on one side. If your router wanders away from the fence, you've ruined the MST after you've gone to all the trouble to engineer it to mount on your saw properly.

          The other risk is that you'll be starting and ending your router very near the front and rear rails. It shouldn't be a problem, but the consequences of a slip in either of those two locations are pretty dire.

          I also have a question: why do you want the miter slot table on the right? The reason why I ask is because unless you make all your cuts with the rip fence on the left (not that there's anything wrong with swinging to the left), you won't be able to use the MST to hold featherboards, which is the most frequent thing I use it for.
          Marc

          Comment


          • #6
            Mike, I too was a little hazy on what you were trying to do, and why, but thanks to Marc, I think I now "get it."

            IMO the main issues are summed up in your two questions about possible weak points in the whole idea:

            "1) It's very hard to get the base in the same position every time, even if it doesn't need to be parallel to the base?"

            That suggests to me that you will be taking the base on and off the saw, and normal asssembly tolerances will be enough to throw the positioning (and thus the slot's parallelism with the blade) off enough that you'll have to check it and probably adjust it. Which means that I don't think it materially matters what precautions you take to actually cut the slot so that it's parallel to the blade. As soon as you move it, you're back to Square One.

            "2) I am too optimistic about the parllelism of the rip fence and the blade?"

            Possibly. You'll be aligning the slot to the blade indirectly, with the rip fence as a middleman; any error in the rip fence's alignment will be transferred directly to the slot. You'll also have a second opportunity for an error, here. Will they compound, or cancel? Granted, the errors may not be enough to truly matter; but at least in theory, it'd be better if the slot were referenced directly off the blade.
            Larry

            Comment


            • #7
              I think the main argument for not doing this is most of us "toe-out"
              our rip fence during setup so we don't get binding cuts. Although
              your miter slot will be parallel to the fence, it may not be parallel
              to the blade which is the whole point of a miter slot.

              However, if you're fence is perfectly parallel to the blade, then
              I think this is an excellent idea.


              Paul

              Comment


              • #8
                Thanks, Marc, I think I get it now.

                Mike, I think you're reasoning is sound, but I'm not sure that your "simplification" really simplifies anything. Like Paul pointed out, you'd have to spend time assuring that the rip fence is perfectly aligned to the blade before cutting the slot.

                You could just as well spend that time aligning the slot to the blade, and then shim the front or back as needed (the space between the saw table and your miter slot fixture). The shim could then be permanently attached so that you'd have the quick on-and-off functionality if that's what you're after.

                I think checking parallelism of the slot to the blade is one of the easier things to check, with a simple jig and a dial indicator. In fact, that's a check I would want to do every time I re-installed a miter slot fixture.

                Regards,
                Tom

                Comment


                • #9
                  quote:Originally posted by Mike P. Wagner

                  I am a new owner and a long ways from making a miter slot, but I am thinking about. When I looked at the designs and the articles that I have read here and elsewhere, I wonder if there is a simple way of making a simpler miter slot.

                  Two things strike me as I look at the saw, and the other saws I have seen. Do these simplifications make sense?


                  1) Miter slots on other are almost always fixed - there is little need to move them along the fence rails - they may need to be removable, but they really don't need to slide. The only thing that is necessary is that the base that contains the miter slot be able to be reliably replaced every time I put it in - it doesn't need to be parallel to the blade, as long as I put it back in the same way every time.

                  2) People seem to want to cut the miter slot first, and then adjust the base of the miter slot - why not do it the other way? If I follow #1, and develop a method for placing the base in the same place every time, then why not use the rip fence (which has been carefully adjusted to be parallel to the blade) as a guide for the router?

                  This leads me to think of building a miter slot the following way:

                  1) Use a piece of MDF (or something else that is pretty stable). Slide the left edge of it against the right side of the center portion of the saw. There may need to be some T-nuts to hold it in place, but they are not needed to make sure it's parallel.

                  If the left edge of the MDF "base" isn't stable enough, route a little rabbit in the edge of the MDF, and screw/epoxy a piece of angle iron to the edge of the base - the point again being that the base doesn't have to the parallel to the blade - you just need to be able to put it in the same place every time.

                  2) Put the piece of MDF in place.

                  3) Adjust the table saw fence so that when a router is held against it, a router bit will be more or less in the center of the the MDF.

                  4) Run the router along the saw table fence to cut the miter slot. If the fence is parallel to the blade, then the miter slot will be parallel to the blade.

                  Is the weak point in this design:

                  1) It's very hard to get the base in the same position every time, even if it doesn't need to be parallel to the base?

                  2) I am too optimistic about the parllelism of the rip fence and the blade?

                  Just thinking,

                  Mike
                  If you look on my web site at the shop equipment you can see one...

                  I am not sure if I looked at the article here. As I recall I went to HD -- looked at one, then bought a piece of Maple..

                  I used a bit of plywood to build it up where there were height differences.

                  To me it was simpler to use the saw to cut the slots.

                  Couple of bolts and we were in business.
                  Will R.
                  http://woodwork.pmccl.com

                  Comment


                  • #10
                    quote:Originally posted by WillR



                    If you look on my web site at the shop equipment you can see one...

                    I am not sure if I looked at the article here. As I recall I went to HD -- looked at one, then bought a piece of Maple..

                    I used a bit of plywood to build it up where there were height differences.

                    To me it was simpler to use the saw to cut the slots.

                    Couple of bolts and we were in business.
                    I really liked your outfeed table - where did you get the brackets that fit it to the fence rails? I will probably need an outfeed table before I need a miter slot.

                    Thanks,

                    Mike P. Wagner

                    Comment

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