Dadoing techniques

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Using a router to make dados. June 24, 2002

I always use dadoes in my case construction. What is the best way to make the dado? I am trying to set up for increased production and I want to get a piece of dedicated equipment for dadoes. I currently use the table saw, but this leaves room for error if the thickness of the plywood changes, since the piece is on top of the blade. I have never seen a router set up for this, but I have heard them talked about.

Forum Responses
If you rabbet the horizontal members, you can control the thickness of the tenon. If you install the horizontal members with the rabbet on the top, you can mask any discrepancies between tenon thickness and dado thickness. This will also allow you to do all of your indexing from the bottom of the cabinet.

We have a router installed on a linear guideway. This guideway is connected to an air piston and produces a hold down clamp. The clamping action flattens your plywood and the linear guideway makes the router groove go straight. This system is marketed under the name Super-dado.

I am now a firm believer in using routers for dadoing. I used to have a dedicated table saw setup, and adjusting the blades for certain thicknesses can take a lot of time. Now, you can buy any width bit to fit the different variations of plywood and get the cleanest dadoes, consistently. A couple of my routers are installed on plates to fit my panel saw and I've cut lots of production time and freed up a little space.

From contributor B:
A panel router is the way to go. It works from the face of the panel and cuts uniform depths every time, plus you can start and stop the dadoes easily.

We have a Safety Speed Cut panel router, but there is also a Her-Saf that works pretty much the same. Always perfectly square, always adjusted and ready to use with little or no setup time. Her-saf makes router bits that are easy to change and have all sorts of cutting widths for plywood (under 3/4"), melamine (15/1000 over 3/4"), etc.

We cut and band parts, then dado on the panel router, stopping the dado about 1/2" from the front edge. The pieces that go into the dadoes are notched the depth of the dado (3/16" in our case) back about 1" from the front edge on a router table we set up just for that. We flush up the front edges and nail the box together. Stretchers front and back give you a place to rest drawer slides when installing them with the slides being square with the front. You have wood to wood joints in the dadoes so that glue will add a lot of strength to the case.

The panel router we have sets against a wall, taking little room in front of it. You need room at each end for feeding panels into it. You can set the router at a fixed position in height and push panels through it as well as running the router up and down.

Contributor B, what stop system do you use with your SSC router to locate the dadoes? We have a SSC but we don't use it much because of the trouble locating the dadoes. Currently we use a table saw for ones close to the edge and a plywood T-square with toggle clamps for ones in the middle of a case. I do not like to see the SSC sitting there doing nothing.

From contributor B:
I added melamine to the frame as follows. 19 1/2" high x 1 1/4" thick at the bottom to get the working height more comfortable. I added 1/2" thick x 42" long pieces at each end, making the panel 1 3/4" thick at the ends to keep panels from falling off easily. This has plastic laminate on top so things will slide nicely and a removable piece in the center, recessed 1/8" from the face, which we change once in a while after using a bit that is wider than usual. Most of our dadoes are 3/4" wide; having the cut in the removable piece 3/4" wide makes it easier to line up pencil marks on the pieces we want to dado with the cut below.

Then I added 1/2" x 4" to each metal crossbar, screwed on with countersunk machine screws, to have a smooth, non-marking back. I didn't like sliding panels on the painted metal frame. We just clamp a piece of 5/8" thick wood to the 1/2 x 4 for stops; we make marks on the melamine for frequently used stop setups. I put a self-stick sanding disc on the bottom piece of 1/2 x 4 behind the clamp so things stay in place when routing. The melamine alone was just a little slippery and sometimes things would move around. Not real pretty, but it works fine.

A panel router is simple to operate/maintain/change tooling for different material thickness. Only way to fly. I strongly recommend air clamps to speed production.