# Long Shelf Dadoes



## LordPadriac (Dec 1, 2014)

I dread asking this question here as my first post on Lumber Jocks (lurked for a time) and I'm not even certain if this is in the right forum. I was treated pretty harshly by several weekend professionals on a home improvement forum for asking the same thing. I got plenty of trash but no real answer or discussion on the subject so I must risk asking again somewhere new.

Since I became really unsatisfied with the results using a dado set on a table saw produced and started looking at using my router for dadoes, rabbets and half lap joints; I have found no end to the variations of basically the same jig for cutting dadoes the perfect size of the shelf stock. They all seem to have the same short coming though and that is that they can't handle dadoes longer than about 24" or less. For many things this is fine but what about longer dadoes? For instance a built in I will be starting soon will have two long shelf sections of almost 5' wide (I'll post that in the projects when it gets under way.). The rabbets I can run with a ball bearing set I have from Whiteside so I don't really care about the long rabbets.

Without using the table saw, the shelf sections have me concerned with how I'm going to line up the dadoes accurately with the sides and cut them to the correct width. None of the jigs I've run across seem to answer that problem. Is that because no one dadoes the back of cases for shelves? That, to me anyway, is a very weak design ideal but maybe that's commonplace now? On the table saw it would be easy to get the cuts lined up on each piece but then you get all the normal problems that come with table saw dadoes. Is there another way to do such long dadoes without the table saw or will I be designing my own jig for the task?


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## fuigb (Apr 21, 2010)

What is your stock? Depending, I'd cut the bloody dado from one big piece of plywood and then rip the sides from the piece and leave the back. What am I missing in your design?


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## Woodendeavor (Apr 7, 2011)

I find it easier to make my own jig for router dadoes. I start with two left over rips of plywood that have straight edges and with more scrap screw them together the exact distance apart that my dado needs to be. Can be made to what ever length you need. Use a template router bit and cut your dadoes. Unscrew the jig and keep the plywood until next time. That is my procedure, I am sure there are many ways to skin this cat


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## bobro (Oct 24, 2014)

Not sure if I get your question because one answer seems so obvious: clamp whatever it is you're using to make the back, all together as it's going to be, to a large flat table, clamp on two boards on either side of the centerline of your dado, as fences, and have at it. There's no place for the router to go other than the dado, provided you've spaced the fences right and everything's tight.

Still trying to figure out your question, do you want, for example, a dado say, 1/2" wide, 18" down from the top on six boards, so that when the boards are placed side to side the dados all line up exactly to form one long dado? (actually the same task as described above, but without the space required for a dry assembly)

That's simple, too, but easier to do than to describe. If my description fails, I'll try to get a camera and do a drawing.

What you do is build, out of scrap boards the same thickness as your stock, a kind of 3-sided receptacle for the boards you're cutting the dadoes across. You clamp this to a table and slide each board in, to the end. On top of this receptacle you clamp your two fences, equidistant from the centerline of the dado, and however far down from the stop (the end of the receptacle) is needed. You reckon bit width and router base, of course, or template bit as Woodenendeavor said.

Shim the fences up just a hair, a single thickness of fine sandpaper will be enough.

Now you slide each piece of stock into the receptacle. (This is why your fences are shimmed up a touch, so the boards will slide under). Each board will stop at the same place. Each will pass under the fences strapped across, and the fences will stay the same in relation to the stop and the end of the board. The router will have a flat surface on either side to start and exit the cut, so the base of the router will always be registered (rocking about is the bane of routing of course).

You can do this with stopped dadoes as well, just put in a stop from the side.

Hopefully this is helpful.


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## bobro (Oct 24, 2014)

...if you just want to make a long dado across something already assembled or some big stock, then I really don't get how there's a question, because you just put two parallel boards across as Woodendeavor described.


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## muleskinner (Sep 24, 2011)

Woodendeavor has your answer. Use the rabbet on your shelf to set the spacing for your jig and you're good to go.


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## LordPadriac (Dec 1, 2014)

Woodendeavor it is a case of over thinking it. That and still being a bit new to the thought of taking the big router out of the table. Your idea makes an embarrassing amount of sense. Thanks.


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