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How Do You Cut an Inside Corner 45 Angle?

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  • How Do You Cut an Inside Corner 45 Angle?

    I have a problem that I hope someone can answer. How do you cut baseboard for an inside corner of 45 degrees? I understand the concept of coping an inside 90 degree corner but that doesn't work on an inside 45 degree corner. Most walls with a 45 degree wall leave an angle of 135 degrees so cutting 22 1/2 degrees will work. (I hope this makes sense)

    I am using a 12" DeWalt Double Bevel Compound Sliding Miter Saw and the vertical clearance does not fit the 7 1/4" baseboard even though it only cuts 60 degree to the left and 55 degrees to the right. I'm thinking I need to cut miters at 67 1/2 degrees each, but not sure how to do it.

    I appreciate any help.

  • #2
    Coping it won't work?


    • #3
      buckaroo01: Think about it for a minute--if you want to mitre an inside corner of 90 degrees, you set the saw at 45 degrees for each cut. Thusly if the inside corner is 45 degrees you make each cut at 22 1/2 degrees. HTH


      • #4
        I haven't actually tried this, but I would think you could make shims to rest on the bed of the saw to make the baseboard sit at an angle. The shim only has to allow the baseboard to rest at a 12.5 degree angle up from the bed (or 77.5 from the blade when vertical) , then cutting from either side of the saw blade, the head can be tilted to cut at 55 degrees to make up the remaining on your 67.5 degree cut.
        To make this a little safer, you could hot glue the shim to the bed and put a layer of on top of the shim sand paper to help grip your baseboard.
        I hope this makes sense...


        • #5

          Is your problem that the saw won't rise up high enough above the table? Maybe you can rotate the baseboard 1/4 turn privided there are 2 flat sides.

          While I doubt this very much, in my mind I picture something more like a RR tie being cut and only a huge radial arm saw would get that job done. I have heard of cases with very large crown molding and the need for a monster size CMS to cut it. How about a large manual compound miter box? Some of them take large work and they are safer for the user.


          • #6
            Several other options:
            1. Cope it as A & P said. Bevel the base board at 45 degrees (both pieces). But one up against the corner and slid the other one to it. With a pair of dividers, scribe the profile off the one that is flush to the corner onto the other one with the divider set at the same width as the boards are thick. Cut along the profile line with a coping saw to get a flush fit. If the top is square, you will have a butt joint instead of a miter, but it will be a tight fit. If the baseboard is painted, run a thin bead of caulk in the joint and smooth it out before painting.
            It will be a little tight to get the dividers into such an acute angle, so you may have to tweak the cut with a rasp or sandpaper wrapped around a dowel to get a perfect fit (especially if the angle isn't exactly 45 or the walls aren't plumb, which is usually the case).
            2. Cut it with a hand saw (the more teeth per inch the better) and tweak the fit with a sanding block. If cutting with a coarse saw, clamp a piece of scrap to the back of the cut (traditional push saw) or front (Japanese pull saw) to prevent tearout.
            3. If you have a belt sander, clamp it upside down in a vise. Bevel to 45 and finish achieving the 67.5 angle with the sander.
            Just other ways of getting a tight fitting joint.
            Practicing at practical wood working


            • #7
              If I were you, I would do these steps:

              1- Check angle, divide it by two.
              2- Clamp or screw one L shape fence 90 degree to the fence.
              3- Set your saw exactly @ haft the inside corner plus haft degree.
              4- Put your stock agaisnt your 90 degree fence and make your cut.

              Pratice make perfect. Try it and you will love it. I even do crown with this way.

              Good luck



              • #8
                I'm going to try some of the ideas that were posted tomorrow. I'll let you know how it works. Just measuring the angle, 45 degrees and dividing it in half gives 22 1/2 degrees. This does not work on an inside 45 degree angle, I tried it and believe me it is not even close.


                • #9

                  Originally posted by buckaroo01 View Post
                  I'm going to try some of the ideas that were posted tomorrow. I'll let you know how it works. Just measuring the angle, 45 degrees and dividing it in half gives 22 1/2 degrees. This does not work on an inside 45 degree angle, I tried it and believe me it is not even close.
                  Is it possible to post a picture on this?
                  Last edited by FSK; 11-09-2006, 01:13 PM.


                  • #10
                    Every one is thinking wrong here. Yes the cut is 22.5 degrees but that is from the fence. Which means you need to set the saw at 67.5 degrees which most saws cannot achive.
                    SSG, U.S. Army
                    K.I.S.S., R.T.F.M.


                    • #11
                      Time for a hand saw and a protractor, I think


                      • #12
                        hello, I am new here; and would hardly consider myself an expert at installing crown molding. I found myself in a similar situation last weekend. This web site wast quite useful to me I hope it helps.



                        • #13
                          Inside 45 Degree Cut Completed!!!

                          I completed the inside 45 degree angle cut using the compound miter saw. I cut a 2x6 with a 45 degree angle and layed this flat on the bed of the saw. I then used a brad nailer to fasten the baseboard to this 2x6, then set the saw at a 22.5 degree bevel then made the cut.

                          The only problem was holding the baseboard in the air while the cut was made, but it worked.

                          Thanks for the many replies.


                          • #14
                            22 1/2 degree cut

                            The only options you really have here are a) use a tenoning jig on a tablesaw to hold your board vertical or b) a coping cut. However, you noted you're using a miter saw... soooo, you'll just have to cope (pun!).

                            Oop, just saw your posted solution. Good thinking!


                            • #15
                              If I am reading this thread right your inside angle is not really 45, if it is it is avery sharp inside angle, I believe it would actually be 135 thus half would be 67.5 and what you have to figure out is how to cut the 67.5 angle