Can a router's pattern trimming bit be used to cut dados?

[javeryh]

I've decided that the cheapest and most accurate way to cut out straight lines for my cabinet will be to use a circular saw free hand to make the rough cuts (about 1/8" away from the actual lines) and then use some clamps, a straight-edge and my router with a pattern trimming bit to make the lines perfectly straight.  I am just wondering if I can use the same bit to cut dados in the wood for assembly.  I have a 3/4" pattern trimming bit and since the plywood I'm going to use is 3/4" I thought I would be able to kill two birds with one stone...  anyone know?  Thanks!

[mpm32]

You can use a top mounted bearing pattern bit for routing dados.  However your bigger problem will be that the plywood that you think is 3/4" is really 23/32" not exactly 3/4".  So, if you use your 3/4" bit, the dado will be slightly large.  They make undersized bits for so called 3/4" ply.

Also, if you have the straight edge, you might as well use the circular saw for the cuts with the straight edge.  You're making more work for yourself otherwise.

Now if you made a fullsize pattern and zipped around that, that would work well.  I usually never make a pattern for just a one off project.  If I am making multiples then that's another thing all together.

[javeryh]

Thanks for the reply.  I guess I won't be using it for the dados after all...    The reason I don't want to use the straightedge for the circular saw is that I don't think it will be as accurate for some reason...  

[RayB]

What's a dado?

[mpm32]

A good blade and good technique and you will have accurate cuts.

[javeryh]

What's a dado?

It's a channel or grove cut in a piece of wood so that another piece of wood (or whatever) can be fastened to it at a 90 degree angle.  It is a stronger joint than just placing the boards at a 90 degree angle.

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Sweet pic, eh?

[KrawDaddy]

Hey,

All you need is a straight cut bit (nice to have a mill blade on end of Bit) and a stright edge.  Assuming you have a plunger router.  Just set your depth at 1/4" and cut right to left against a straight edge.   (distance between bit and edge of router base)  To change directions allow plunger to rise, reset straight edge and carefully replung)

For straight cuts use your circular saw or jigsaw to rough cut your work piece about 1/4" too big and setup your straight edge, set straight bit to 7/8", and use the router to get the perfect straight cut.

You will not be disappointed but it takes longer

Kind Regards\

Kraw

[neuromancer]

It's kind of hard to cut dados with a circular saw though!

I have cut dados with my router by using an undersized bit and making more than one pass. Results are sort of mixed -- it's hard to align the straight edge exactly perfectly.

Bob