February 12, 201313 yr  A while ago there was a thread about undersize plywood. It got me to thinking about how best to compensate for the irregularities in ply when using a router to dado.  So I came up with this: And of course you need a top plate to which to mount the router: Some sliding nuts to go in a T track routered in the base will be nice: And a couple of keys  If the plywood for the base is not thicker than your ply that you are using for the other part of the jig - the main dado jig - the one that runs at a right angle to the board being dadoed then you can just make the top plate and the keys a little shorter so they don't bump into and ride i up over the main dado jig. You could also skip the slots for the allthread in the base plate altogether and just glue a screw or length of allthread in a hole or use a hex nut & Washer and glue them in a counterbore in the bottom of the base plate
February 12, 201313 yr Cliff, that is very ingenious! Great work and great engineering. And, great graphics!!!! Thank you for sharing your concept. I do not see a flaw in that, it should work. I have also found these guys pretty handy for undersized ply's, the fit is nice and tight and with a straight edge guide it works very nice. Whiteside 3-Piece Undersized Plywood Dado Router Bit Set With 1/2" ShankItem #150756$55.99 But back to your jig, very nice indeed, watch out, you better start trademarking this stuff, they are lurking on sites like this looking for concepts just like this to steal! John MorrisThe Patriot WoodworkerProud Supporter of Homes For Our Troops and Wounded Warriors Project
February 12, 201313 yr Author Glad ya liked it.I was going to get a set of undersize bits and then I considered that there is nothing tying the bit to the ply industry. Which is to say that they can mess with the sizing willy nilly and the new bits may, or not, continue to fit. So for me, the better course was to be able to make the slot fit whatever the wood came out to.Also handy when one gets a tad off when planing (DAMHIKT).
February 12, 201313 yr That's a nice Jig, Cliff.If I understand your concept, would this jig would slide along a straight edge which would be clamped to the work piece being dadoed?Lew Kauffman-Wood Turners Forum HostTime traveler. Purveyor of the world's finest custom rolling pins!
February 12, 201313 yr Cool Jig. Excellent graphics.John MoodySite AdministratorJohn Moody Woodworkshttp://www.johnmoodywoodworks.com
February 13, 201313 yr Author Lewis Kauffman said:That's a nice Jig, Cliff.If I understand your concept, would this jig would slide along a straight edge which would be clamped to the work piece being dadoed?
February 13, 201313 yr Thanks, Cliff. The jig I made doesn't require any measuring or moving to make each dado. Cliff said: Lewis Kauffman said: Well there's a world of router jigs along the lines of this sort which I just plucked from the web: and this one Place my little gizmo between guides such as seen in the pic and you can adjust it for gap size.Â
February 13, 201313 yr Author The jig I made doesn't require any measuring or moving to make each dado. No moving? I can see how a jig would be made to accept a particular router base or a router bushing: ergo no need to change the opening size. But no moving the jig for each slot? I'm interested. Got any pics of this jig?
February 13, 201313 yr No plans- got it someplace off the internet but I'll take pix and post today or tomorrow.Cliff said:The jig I made doesn't require any measuring or moving to make each dado. No moving? I can see how a jig would be made to accept a particular router base or a router bushing: ergo no need to change the opening size. But no moving the jig for each slot?I'm interested. Got any pics of this jig?
February 13, 201313 yr Great shop jig, CliffAlso, super job in the mechanical drawings and instructions. Â I'm proud of ya.Fredaka Pop's Shopwww.pops-shop.com'Soooooo many patterns - sooooo little time'Scroll Saw Forum Host
February 13, 201313 yr Cliff, Here are some quick pix of the jig. It should be noted I tend to over engineer everything to the point of absurdity TOP- The jig is really a double T square with a stationary and movable leg. Each leg has a masonite base upon which the router base sits. The inner edge of the masonite is trimmed to the exact edge of the straight cutting bit (3/8" bit for this jig). The jig is clamped on the piece to be dadoed. BOTTOM- Wing nuts to secure the movable guide (arm). On the rite there is an adjustable stop to set the position of the jig when cutting several identical pieces. SETUP- To use the jig, place a piece of stock- the same thickness as the width of the dado- between the guides and adjust the movable arm for a tight fit. Position the jig at the desired location. Route the dado in each direction, keeping the router base against the plywood portion of the arms. A jig like this has its' limitations. The most narrow dado is limited to the size of the initial bit/jig design. In this case- 3/8". Also, some routers have round bases (Porter Cable) and the base may not be perfectly centered on the router. If this is the case, the router orientation- when the jig is created- must be maintained or the dado width and jig calibration will be changed. Lew Kauffman-Wood Turners Forum HostTime traveler. Purveyor of the world's finest custom rolling pins!
February 13, 201313 yr Author That's a sweet dado jig.  The kinds that adjust like yours and those that don't require a router bushing can also accept pother tools like the venerable jig and circular saws. I have one I have yet to put dimensions to that uses an elliptical mechanism to adjust the router position and can also tell the user where the cutter is within 0.005" by merely positioning it to some little 1/16" dia brass plugs. Here is a first look at the assembly
February 13, 201313 yr Nice! Being able to accurately center the router would really tighten up the dados and keep the jig edges from getting chewed op.Cliff said: That's a sweet dado jig.  The kinds that adjust like yours and those that don't require a router bushing can also accept pother tools like the venerable jig and circular saws. I have one I have yet to put dimensions to that uses an elliptical mechanism to adjust the router position and can also tell the user where the cutter is within 0.005" by merely positioning it to some little 1/16" dia brass plugs. Here is a first look at the assembly
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