Router dado jig

[Curt Harms]

There was a thread about cutting dados with a router. I have a project in the works that requires dados so decided to take some pictures. Here's the jig I built. It's just MDF with wood liners. The router bit bearing runs against the 'jaws' and I don't know that MDF would wear well
jig1.JPGjig2.JPG
I just draw a line where I want one edge of the dado to be and align the fixed jaw of the jig with that line and clamp the fixed jaw
jig3.JPG
I set one of the shelves against the fixed jaw and move the movable jaw tight against the shelf and tighten the thumbscrews. They should be knobs, knobs would be easier to tighten.
jig4.JPG
I used a Grizzly trim router with 1/2" X 1/2" pattern bit. The cutting length of the bit has to be short enough that the bearing will ride against the jig not above it.jig5.JPGjig6.JPG
One pass up the left side and down the right side. Done.
jig7.JPG

It's taken longer to describe it than to do it. I like the router jig method for two reasons. One is that the dado bottom and sides are very clean. Clean accurate cuts should result in good strong glue joints. The second reason is easy size adjustment. We all know that plywood can be variable in its thickness. A jig like this makes it easy to adjust the dado to the plywood thickness. The biggest shortcoming I can think of is that it will only cut dados 1/2" wide or wider. There is a similar setup that uses collars and straight bits rather than bearing guided bits. That configuration will cut dados as narrow as the available straight bit. Thanks for looking.

[Paul F Franklin]

Good example of a useful jig! Designed and built to do a good job for a long time without a lot of unnecessary effort.

[Bruce Wrenn]

Instead of using faces of jaws to guide bit, use a fence to guide the edge of the router base. Base has to be centered on bit for this to work. My router of choice for this is an old Dewalt 610, as it has rack and gear height adjustments. My favorite cutter is a HerSaf, 1/2" reverse helix screw on cutter. To make fence, add a piece of 1/2 inch plywood to a piece if 1/4" ply wood. Using router, riding against fence, trim 1/4" plywood. When using this type jig, rub a dryer sheet on both bottom and edges of router base.

[Curt Harms]

Good example of a useful jig! Designed and built to do a good job for a long time without a lot of unnecessary effort.

Thanks Paul. Nuthin' gold plated 'bout that but it works pretty well.

[mike stenson]

Instead of using faces of jaws to guide bit, use a fence to guide the edge of the router base. Base has to be centered on bit for this to work. My router of choice for this is an old Dewalt 610, as it has rack and gear height adjustments. My favorite cutter is a HerSaf, 1/2" reverse helix screw on cutter. To make fence, add a piece of 1/2 inch plywood to a piece if 1/4" ply wood. Using router, riding against fence, trim 1/4" plywood. When using this type jig, rub a dryer sheet on both bottom and edges of router base.

I'll be honest, using a bearing guided (pattern) bit has advantages. Unlike the above type of jig (which I have several of), you're not stuck with a specific router and bit combination.

BTW, I use the type mentioned in this post with a non-round router all the time. I just have one side that MUST be referenced off of the flat edge (another limitation).. but I've already got them made for the majority of tasks I need.

To the OP. Nice!

[Von Bickley]

I made one that is similar to Curt's and it works great for exact width dados'.
dado2.jpg

[Jim Dwight]

I have a jig like that and it can work well. I found that I needed to add a little clearance to get things to go together easily. I have some business cards (my left overs) that I use for this shimming with one or two cards for clearance.

More recently I got some undersized router bits and I like to use an accessory to guide my router with my track saw track. Works very well. My current project is using some plywood that turned out to be 3/4 so I did not need an undersized bit. It's nice to be able to use a simple cheap straight bit.

[Eric Arnsdorff]

Nice job! I'll give this a go the next time I need to make some that my router table can't handle.