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When I look around at the jigs I have been amassing it's a bit frightening. So much so that I recently discovered that I have made 2 jigs that do exactly the same thing. One of them I made about 15 - 20 years ago, and for the life of me, I do not know where it went for most of it's life and I needed the same functionality about a year ago, so made that same jig again and soon after found the original ...
Maybe if I had made a dual purpose jig back then ... a jig that did more than one job I might got a bit more use from it and maybe used it a few time over the years instead of squirrliling it away in my wood storage room where is eventually got forgotten about. Well, time to make another jig, this time a dual purpose, and maybe I can even get it to do more?? Wouldn't that be nice, a multi purpose jig ... I must work on trying to make more of my jig do more kinds of things.
This router jig for cutting dados is something I have been meaning to make for a long time. I often need to cut one or two quick dados and setting up my dado blade on my table saw, making test cuts etc. Is a lot of time for what should be a short process. The other thing that I need that is along the same vein is a jig that I can use to cut slots ... in even more jigs I want to make, so why not make a jig that does both?
The dado cutting jig has been around for many, many years now and it's a tried and true system, so what I am making for the dado cutting side has been done before. What I have never seen (not saying it's not out there somewhere, just that I have never seen it) is a jig that combines cutting sliding slots and dados combined in the same jig.
I have an idea for another table saw jig I want to make, yes another multi purpose jig and it is going to need slots, so now is the perfect time to make a jig that will do that.
The basis of the dado cutting side is pretty straight forward. I cut 2 sets of Baltic Birch plywood one set 6 inches wide by 20 inches long, the other 2 inches wide by 20 inches long. The 2 inch pieces I cut a 1/4" slot into so that they could be used as sliders, as shown in the video. I glued both 2" sections to one of the 6 inch sides upper and lower the drilled the second 6 inch piece to accommodate the slot.
Testing the Dado and solving solutions
The first test of cutting dados with this jig were disappointing. The second test was not much better so I went about discovering why. What I learned is that you are best to NOT use a whole board when sizing a dado slot. The reason for this is that most boards are slightly warped and this is enough to create dado slots that are just slightly too wide. The problem arises when the board you are using to measure with is slightly warped and will therefore create a dado that is loose.
The best form of setting the width is to only use a small piece of the board you are using as a width guide ... use a corner on one side of the, then use the other corner on the other side. This will ensure your dado cut is exactly the width of the board and not being masked by warped or cupped boards.
Another solution I found that worked well is that I felt the slot in my jig needed to be cleaned up a bit. I inserted a thick veneere in each side of the jaws then aligned the veneer with a blade in my table saw, re-set the height then recut both the slot. This also helped ensure my slots were parallel and were cutting the optimum dados possible.
Testing the Solt
I had similar issues when testing the slot making capabilities. I had to make 2 test cuts before I was happy with the results. What I determined is that the thin strips used as spacers need to be near perfect in width otherwise the slot sides are too big or to tight. After a couple of tries I got them near perfect for the t-bolts that I am using.
The second part was of the jig was pretty much as easy, but in this case I needed to drill 2 parallel slots on each of the 6 inch boards and make them parallel on each board. I then drilled a hole in each of the 2" pieces so I now have a second set of sliders.
The trick in using the second set of sliders that will be used to cut slots is that they need to be wide enough to accept the thin side of the slotted t-bolt which means that the sizing plywood strips need to be the same width as the area between the flat side of the t-bolt and the shaft.
Using 2 spacer pieces mean you can place both strips on each side of the router and that will create the slot area. Split the wood spacers, one on each side and cut a slot down the middle and this will create the slot that the t-bolt shank will fit through and now you have a wooden sliding t-bolt slot.
After doing a tiny bit of fine tuning the jig is working better than I expected ... and it's 2 jigs in one, which means I will get twice the usage out of one signal jig ... a great way to ensure it gets all the use possible ....
Copyright Colin Knecht