Box (finger) joints - table saw or router

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  • Box (finger) joints - table saw or router

    I’m planning a project to make a small box with finger joints. I have a bt3000, dado blades and a router. I’m wondering which is the best way to go. I don’t have a box (finger ) joint blade. I’ve seen plans on YouTube for using table saw or a router and I’m unsure of the way I should go. I would probably use my stack dado blade on the table saw or a 3/8” bit on my router. Would using a dado blade create small ridges ar the bottom of the cut that would require cleaning up with a file?

  • #2
    I've done it both ways and prefer to use the router. I have a Freud 8" dado stack and the bottom of the dado is not nearly as smooth as with a router bit. Note that when using a router you need to back up the board being cut with a spoil board to prevent tearout on the backside of the cut.
    Chr's
    __________
    An ethical man knows the right thing to do.
    A moral man does it.

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    • #3
      I agree that a table mounted router is the better way.
      just another brick in the wall...

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      • #4
        I prefer the table saw. I think TS dadoes make a cleaner cut.
        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

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        • #5
          Originally posted by twistsol View Post
          I've done it both ways and prefer to use the router. I have a Freud 8" dado stack and the bottom of the dado is not nearly as smooth as with a router bit. Note that when using a router you need to back up the board being cut with a spoil board to prevent tearout on the backside of the cut.
          But aren't the dado blades supposed to produce a flat bottom? I have been planning to acquire a set someday hence asking.

          NG

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          • #6
            Originally posted by nicer20 View Post

            But aren't the dado blades supposed to produce a flat bottom? I have been planning to acquire a set someday hence asking.

            NG
            It depends on the dado set you are using. A wobble or adjustable dado will give you a slightly rounded bottom. Some have sets have pointed shearing cutters on the outside edge that make for a clean cut at the edges of the dado but if you look at it from the end, you get what I call bat ears on each side of the bottom. If your chippers aren't perfectly aligned or machined precisely, you may get slight differences in depth. None of these significantly change the functionality of the joint, but all can affect the appearance. All of these issues can be resolved by cutting a little too shallow and cleaning up the bottom with a very sharp chisel.

            For a drawer where the joint is unlikely to be examined up close none of these would matter. For a box or a chest where the joinery is on display, My opinion is that you you get a cleaner joint with a router.

            [sarcasm on]Since the responses are two to one for a router, Loring is clearly wrong [/sarcasm off]
            Chr's
            __________
            An ethical man knows the right thing to do.
            A moral man does it.

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            • LCHIEN
              LCHIEN commented
              Editing a comment
              Use what works best for you.

          • #7
            Since I have a very good home made router table, I have a box finger set up for use with routers. I thought long an hard on which will produce the most repeatable and quickest set up for me.

            The hard part for me on a table saw is the kerf width and setting that up with the right width of movement. ON my router table, I have set block sizes and set router bit sizes.
            Hank Lee

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

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            • #8
              Originally posted by leehljp View Post
              Since I have a very good home made router table, I have a box finger set up for use with routers. I thought long an hard on which will produce the most repeatable and quickest set up for me.

              The hard part for me on a table saw is the kerf width and setting that up with the right width of movement. ON my router table, I have set block sizes and set router bit sizes.
              I have one of those Freud box joint Dado sets that has the precise 1/4 and 3/8" dado assemblies and perfect flat bottoms. Pretty much fool proof and instant setup.
              https://www.amazon.com/Freud-20T-Joi...6869590&sr=8-3

              Click image for larger version  Name:	P3270312.JPG Views:	0 Size:	274.2 KB ID:	843490
              Last edited by LCHIEN; 03-27-2021, 03:28 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

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              • LCHIEN
                LCHIEN commented
                Editing a comment
                it is 8" but it fits OK on the BT3 because its only 3/8" wide.you have to take off the 1/2 in spacer
                .

            • #9
              Just stumbled into a purchase of the jointech clincher CL-18 with all the books and accessories for a great price. I am itching to try this type of joinery. Maybe after the honeydoos are extinguished.
              Harumpf!
              GrumpyDad

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              • #10
                Originally posted by nicer20 View Post

                But aren't the dado blades supposed to produce a flat bottom? I have been planning to acquire a set someday hence asking.

                NG
                There are many types of dados. Twistsol's answer (#6) in the thread has a very accurate answer detailing what you get with a wobble, and with a stack with beveled teeth on the outer plates, and those with just flat top teeth. The bevel top outer plates are supposed to make cleaner edges with less tearout by scoring the line before the raking cut. These are the bat ears that Chr's talks about.
                I will add that its important to have all your dado blades on the flat part, not the threaded part of the arbor to get flat bottom.
                Wobble dadoes have a radius to the bottom which is the radius of the blade... a 6" wobble will have more curvature than an 8" because its radius is smaller.
                Note that the picture below exaggerates the wobble some. This shows a 6" dia. wobble dado cutting a 1" wide groove 1" deep...which most cannot do that wide or that deep. If the dado groove was 1/2" wide and 1/2" deep, then the curvature of the bottom would be half as much as shown in relative size. An 8" wobble dado would have even a bot less curvature.
                The bat ears are also relative... probably only a few -.010" or so deep.

                If you want a truly flat bottom you have to pick the dado set carefully.

                I Know so much about dadoes because I own 5 sets: 6" HSS set. 8" Craftsman excalibur Wobble, 8" carbide Freud set, a 6" carbide Freud Set and a 8" Freud Box Joint set. I can say I learned the hard way.

                Here's a little graphic I threw together.

                Click image for larger version  Name:	dado bottoms.JPG Views:	0 Size:	112.2 KB ID:	843494
                Last edited by LCHIEN; 03-28-2021, 02:10 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

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                • #11
                  Thanks everyone - so much to learn !!

                  LCHIEN : Those drawings are super helpful. Picture is worth 1000 words after all.

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                  • #12
                    Here's the reasons for bat ears on many dados.
                    Click image for larger version  Name:	Freud SD206 Dado blades.JPG Views:	0 Size:	31.8 KB ID:	843499
                    Note the angled scoring tips on the right and left outer blades while the inner chipper blades have flat tops to span the bottom.
                    Last edited by LCHIEN; 03-28-2021, 01:46 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


                    • #13
                      Thanks for those drawings. I was completely unaware of a true flat bottom dado sets. I have the first two types although I don't think the wobble blade has been used since the 80's
                      Chr's
                      __________
                      An ethical man knows the right thing to do.
                      A moral man does it.

                      Comment


                      • #14
                        Originally posted by LCHIEN View Post

                        I have one of those Freud box joint Dado sets that has the precise 1/4 and 3/8" dado assemblies and perfect flat bottoms. Pretty much fool proof and instant setup.
                        https://www.amazon.com/Freud-20T-Joi...6869590&sr=8-3

                        Click image for larger version Name:	P3270312.JPG Views:	0 Size:	274.2 KB ID:	843490
                        Done it both ways (Router and Table Saw) I have the same blade LCHIEN shows and FOR ME as long as the box joints are one of those two sizes I prefer the TS ... if there is a big difference I use the router table with a adjustable jig. (INCRA LS POSITIONER)

                        "Like an old desperado, I paint the town beige ..." REK
                        Bade Millsap
                        Bulverde, Texas
                        => Bade's Personal Web Log
                        => Bade's Lutherie Web Log

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                        • #15
                          Since I only have dado blades that are not box joint blades, I’ll make a jig and use my router to make the box joints. Later if I get a box joint blade set I will try that method for future projects.

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