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  • tenon jig

    I built the tenon jig designed by Jim Frye a few days ago. I was careful to precisely trim pieces to go into the rip fence, so that they were a snug fit. I have an Incra LS positioner, so that came in really handy for shaving pieces down a few thousand for a precise fit. The positioner was also used to precisely cut the rabbits for a snug fit.

    I think the uprights using this design really help to keep the whole thing at a true 90 degree angle to the table. Anyway, within a couple of hours it was complete. I used some paraffin wax to make it slide a bit easier.

    Anyway, I was cutting some very small 4" x 5" raised panel tops for a small box. On something this small, it's really hard to do any sanding after the fact and not destroy crisp look of the corners. With this said, it's very important that the cuts are precise. I was also using a 60 tooth blade to insure smooth as possible cuts.

    The problem I'm having is there's a bit of slop in the jig itself. I would think the little pieces of wood that go into the slots of the rip fence would prevent that, but if they're too tight the jig will not slide along the fence.

    So, I'm rather disappointed in the amount of play. For now, I'm just careful to put pressure downwards on the jig along the fence, and move the jig forward only to prevent any lateral motion. If I pause or shift the pressure, the jig will rock. The saw blade will then leave marks on the finished piece. Even 1/16th is too much in this case.

    I thought about adding a piece of wood to the jig that would lay flat on the table surface, and perhaps that would keep the whole jig more rigid. The only issue there is the fence is to the left of the blade, and I have to remove the SMT, so there really is no support there. I have an Incra LS positioner attached to my router table extension, so I prefer not to move this every time I want to use the jig, but I may have to or build another small extension table.

    So, that got me thinking to whether or not buying the sliding miter slot extension would be a good idea. Having a 3 or 4 inch bearing surface I would think would help to keep the jig flat and true. I can also then buy a commercially made tenon jig, although I think there's hope for a homemade type.

    Just wanted to get feedback from others on what they found works well. This is one jig that needs to track precisely, and so far I don't seem to be able to get that kind of precision I need.

    Troy

  • #2
    My first reaction is to ask if there is any chance your fence is the problem? The BT fences lock down at the front first - to align properly - and then the back clamps down to make sure the fence doesn't flex. If the rear lock is not right/tight then the far end of the fence can flex to/from the blade slightly as you apply lateral pressure to the fence.

    Otherwise... instead of shims to adjust jig-to-fence clearance consider using a thicker piece between the jig & fence - on the side of the fence opposite the workpiece itself - that is positioned by a series of set screws. This way you can easily fine-tune the clearance of the jig in response to normal wood movement due to humidity. Basically you'd be mimicking the shim & setscrew assembly inside the BT's blade & motor support system. Waxing the jig materials helps... but I've had better luck using naturally slippery materials for the jig pieces that ride on fences or the tabletop: melamine, the white ultra-high-density-plastics, etc.

    It's also fairly easy to make a flat board that can sit between the main table top and the sliding miter table (SMT) piece instead of buying the dual miter slot piece. Just rig up a flat board or two that sits on the rails, even with the table top, and has small rectangular feet to slip into the rail slots. That'll hold it front-to-back and let it be a support for your jig. There are all sorts of home-made miter slot add-ons posted on this site instead of buying the Ryobi dual slot kit by the way. I used a standard miter slot extrusion screwed to a board of the correct thickness (in a proper sized dado/groove of course) and used screws to attach it to the front & backside aluminum pieces of the saw. It's only one slot wide, not dual like Ryobi's accessory, but it's also a lot narrower so the SMT isn't quite as far from the blade.

    mpc

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    • #3
      I think a little clearance is necessary for you to move the jig. I use mine to cut tenons regularly. Mine is most square to the table with a little twist to the right as I push the jig throuigh. I'm used to it so I usually remember.

      I do not use this jig to cut raised panels, however, regardless of how small they are. I cut raised panels with a high fence extension and the fence left of the blade. My fence extension is melamine particle board so a coat of wax makes it very slick. I also prefer a sharp rip blade or at least a combination blade for this, not a fine tooth crosscut. With the blade buried in the wood there is a tendency to trap dust in the blade gullets which will cause it to shudder a little making a nasty mark that is hard to sand out. Deep gullets on the blade seem to help. Rip blade are the deepest.

      Jim

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      • #4
        I think the biggest problem with this design is the limited bearing surface of the jig itself. We're essentially talking about an inch and a half of bearing surface for something that is 10 or 12 inches tall, so it's no wonder this thing has some slop in it. That's a lot of leverage working against the jig.

        After thinking about this some more, I've decided I'm going to make a jig that works off the sliding miter table. I think the key design feature is a very wide base. Black Walnut had one idea, but I think I'm going to make up something that clamps to the SMT fence, and then has lateral adjustment via some sliding miter slots. Two larger boards on top of one another IOW creating a sled via miter slots.

        The Incra project book has one idea that looked intriguing. Again, I think the key design element is going to be a large flat base, and them some bracing for the vertical piece. Moving the SMT makes more sense than moving the jig itself to me. The SMT is already adjusted to run parallel to the blade, and is silky smooth across its travel.

        so, I appreciate the comments but I think I'm going back to the drawing board on this one, and designing something that makes more sense from the get go.

        Interesting comment about the deeper gullets in the blade Jim. That is one I have not heard before. I don't think I would use a ripping blade for crosscuts, but I could see a combination Blade might have some advantage. I don't think there's any question that a 60 or 80 tooth blade works better for crosscuts though. More of a problem than the blade though, is the movement of the jig itself. Gotta get that worked out first in my mind.

        So, I'll report back when I've got a new jig designed. Thanks again for the replies! Hope you had a great holiday!

        Troy

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        • #5
          I built a tenon jig that attaches to the SMT. I've used it to cut tenons 1.5x6x60" pieces that were 3" long, and I had excellent results.

          My design was based off of black walnut's design, but instead of having the micro adjuster I have the tall fence (18" tall) screwed and glued to the base, and its adjusted along the SMT fence as needed, and while it isn't as easy, I haven't had any problems with that. I do like having the fence that can angle, and I've used that a few times to cut splined joints with great results.
          Alex

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          • #6
            Troy,

            I've used a sharp - emphasize sharp - 24 tooth Freud rip blade to cut oak plywood before. Crosscuts. The cuts chipped no more than a slightly more dull combination blade. So if your rip blade is sharp.... Seriously, you may be surprised how well a rip blade will crosscut - I was.

            Jim

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            • #7
              Originally posted by JimD
              ...I cut raised panels with a high fence extension and the fence left of the blade. ... I also prefer a sharp rip blade or at least a combination blade for this...

              Originally posted by cwphoto View Post
              ...
              Interesting comment about the deeper gullets in the blade Jim. That is one I have not heard before. I don't think I would use a ripping blade for crosscuts, but I could see a combination Blade might have some advantage. I don't think there's any question that a 60 or 80 tooth blade works better for crosscuts though. More of a problem than the blade though, is the movement of the jig itself. Gotta get that worked out first in my mind.
              ...
              Troy

              Troy, i think Jim was referring to the use of a rip blade in reference to the fact he uses it for cutting raised panels on a table saw. Not for crosscuts.
              He goes on to explain that raised panels is a form of deep ripping and I think he's right in that the deep gullets would be a real help for that.
              Last edited by LCHIEN; 12-26-2011, 08:15 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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              • #8
                Originally posted by cwphoto View Post
                So, that got me thinking to whether or not buying the sliding miter slot extension would be a good idea.

                Troy
                What is the "sliding miter slot extension"?
                John

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                • #9
                  Originally posted by LCHIEN View Post
                  Troy, i think Jim was referring to the use of a rip blade in reference to the fact he uses it for cutting raised panels on a table saw. Not for crosscuts.
                  He goes on to explain that raised panels is a form of deep ripping and I think he's right in that the deep gullets would be a real help for that.
                  Hmmm, well, 50% of the cuts are crosscuts in raised panels too! I still don't think I would use anything less than the 36 tooth Blade regardless. I could see were a combination Blade might be a benefit though. Bear in mind that the panels I was cutting were very small, and the cuts not all that deep AND they had no shoulders, so a lot of this is a moot point.

                  Mosty, Jim's comment got me thinking about times where I was using a fine tooth Blade for ripping. Yeah, not ideal but, sometimes I"m lazy and don't change the blade unless there are a lot of rips. Perhaps a combination blade might be a better choice. It is amazing to me how silky smooth a 60 tooth blade does crosscut though. Practically don't even need to sand them.

                  This gets into another topic, but I'm curious how a thin kerf blade vs a slightly wider one would handle things, all else being equal. I've certainly heard it suggested to use a thin kerf blade to make it easier on the saw for deeper cuts, but I imagine it has greater potential to leave saw marks? An interesting topic on its own for sure!

                  Troy

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                  • #10
                    Originally posted by jnesmith View Post
                    What is the "sliding miter slot extension"?
                    sorry John, I think that Ryobi calls it a "dual miter slot extension". Better? Here's a pic.
                    Attached Files

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                    • #11
                      Originally posted by Wood_workur View Post
                      I built a tenon jig that attaches to the SMT. I've used it to cut tenons 1.5x6x60" pieces that were 3" long, and I had excellent results.

                      My design was based off of black walnut's design, but instead of having the micro adjuster I have the tall fence (18" tall) screwed and glued to the base, and its adjusted along the SMT fence as needed, and while it isn't as easy, I haven't had any problems with that. I do like having the fence that can angle, and I've used that a few times to cut splined joints with great results.
                      Thank you for confirming my suspicion about a wider base being key to stability. I too, don't really want to get into making a micro adjuster, but a sliding base via a sled is not too hard to make up. I'll post a picture when I'm done. Thanks again for the reply!

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                      • #12
                        Originally posted by cwphoto View Post
                        sorry John, I think that Ryobi calls it a "dual miter slot extension". Better? Here's a pic.
                        Gotcha. It took me a while to keep these two straight: MST (Miter slot table) and SMT (Sliding miter table)

                        BTW: I have two MST's. One to the left of the blade, and one to the right. Love it. I have jigs that can go on either side, and various sleds with two runners.
                        John

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