Cutting Big Dadoes with a Router

By George Vondriska

A simple jig and a pattern cutting bit make big dados a small concern.

Dado My friend, Tim, showed up recently with the need to make a sign frame out of 4 x 4s. In order to make the frame for the sign rock solid we wanted to cut dados into the vertical posts to received the horizontal parts. How to handle these 1″ deep, 3-1/2″ wide dados.The prospect of crosscutting them on the table saw seemed daunting. An 8′ long 4 x 4 just weighs too much. This project called for taking the tool to the work, not the work to the tool.Back in my carpentry days we’d commonly notch construction grade material by making MANY passes with a circular saw, then chiseling the dado flat. That works OK, but not great. I decided the answer for this project would be a hand-held router, pattern cutting bit, and shop-made jig.

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Making a sign frame – Sizing the jig to the posts / Sizing the jig to the frame:

Cutting Big Dados with a RouterThe Jig. I ran four 2 x 4s through the planer and jointer to make sure the faces and edges were flat and straight.We clamped the 2 x 4s to the vertical post and screwed them together, making sure the assembly was perfectly square.

Cutting Big Dados with a RouterThe router and pattern bit. Next we clamped an off cut from the horizontal pieces between two of the 2 x 4s and screwed the final piece to the jig. Note the .020″ dado shims. This should provide just a little clearance between the routed dado and the horizontal component.The result is a jig that will perfectly straddle the posts and, using a pattern cutting bit, make a perfectly dimensioned dado.

Making the Cut.

Cutting Big Dados with a RouterCutting dados with a hand held router. With the post clamped to a bench the jig is clamped on the lay out lines for the horizontals and the waste routed away. The large diameter of the bit makes short work of the 3-1/2″ that has to be removed.

Cutting Big Dados with a RouterA perfect dado. The result is a dado…

Cutting Big Dados with a Router…that’s a perfect fit. Easy peezey.

Tip: When working with large pieces it’s easier to bring the tool to the work than the work to the tool. Here’s a way to make perfect dadoes with a hand-held router.

Photos By Author



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7 Responses to “Cutting Big Dadoes with a Router”

  1. Mario F. Bournes

    What type bits should be used?

  2. Marty Amberg

    looks good, thanks

  3. Roger

    I don't need 2×4 frame just for photos thanx

  4. Gerry Ostgarden

    I will be turning a polka dance hall into a residents. It's wide open, hardwood, have a new furnace-need to run duct work Set up walls for two bed rooms kitchen bath w/only shower turlet-sink-. where or do you have plans or plan ideas? on DVD or books-sure would like DVDs On wall construction, wiring, vent's, the ceilling is high maybe add a loft. I have experience in this only we had blue prints, like at the Mall of America (do you know where I can sell this stuff also) any way that is the type of DVDs I need-not what tou have sent me alread. In door house reconstruction...Please call 507-766-4423 in Minnesota-Mankato...progect is in the southern Black Hills, Custer area Thank you for your time on this topic...Gerry Ostgarden

  5. aj

    Nice. I have to re-build the frame for my cider press - all done using dado joints like this in 2x4s. Perfect solution!

  6. Gerry Ostgarden

    I will be turning a polka dance hall into a residents. It's wide open, hardwood, have a new furnace-need to run duct work Set up walls for two bed rooms kitchen bath w/only shower turlet-sink-. where or do you have plans or plan ideas? on DVD or books-sure would like DVDs On wall construction, wiring, vent's, the ceilling is high maybe add a loft. I have experience in this only we had blue prints, like at the Mall of America (do you know where I can sell this stuff also) any way that is the type of DVDs I need-not what tou have sent me alread. In door house reconstruction...Please call 507-766-4423 in Minnesota-Mankato...progect is in the southern Black Hills, Custer area Thank you for your time on this topic...Gerry Ostgarden

  7. aj

    Nice. I have to re-build the frame for my cider press - all done using dado joints like this in 2x4s. Perfect solution!