How to cut dados for a bookcase?

[EdL]

Radial arm saw with a dado head.

Ed

[Red Sawman]

Radial arm saw with a dado head.

Ed

^^^^^^^^^ this^^^^^^^  if plywood …. or … if hardwood ... handsaw the sides of the dado and use a shoulder plane or a #39 of the correct width and finish with a router plane. If you use your imagination you could also set up a #46 if cutting cross grain

Red

[mstens]

This has been discussed a bit. But the video linked is really a one-off jig, and I really dislike that if I can avoid it.

If we're talking plywood I'll use a router. Putzing around with dado blades is a pain I do not enjoy. I also do not enjoy test cuts. So I made an adjustable jig. It uses the same router and same bit, always. Just close the jig around the stock used for the shelves and clamp in place. Then run the router on both sides and done.

[Stove M]

This has been discussed a bit. But the video linked is really a one-off jig, and I really dislike that if I can avoid it.

If we're talking plywood I'll use a router. Putzing around with dado blades is a pain I do not enjoy. I also do not enjoy test cuts. So I made an adjustable jig. It uses the same router and same bit, always. Just close the jig around the stock used for the shelves and clamp in place. Then run the router on both sides and done.

[Stove M]

I like the dado blade on the table saw. Being able to use the saw fence to register that each like piece is cut at the same relative locations on matching pieces is a plus for the table saw for me. Yes,  adjusting the blade width and depth requires test cuts (and can be a pain). Either router or table saw, one creates a strong joint!

[mstens]

I like the dado blade on the table saw. Being able to use the saw fence to register that each like piece is cut at the same relative locations on matching pieces is a plus for the table saw for me. Yes,  adjusting the blade width and depth requires test cuts (and can be a pain). Either router or table saw, one creates a strong joint!

Harder to this though, a lot harder actually.




Generally though, I use handsaws, chisels and a router plane.

[Cooler]

When you do this, temporarily tack the sides together so you can cut counterpart dadoes in both pieces at the same time so you know they align correctly.

If I am making the sides from plywood I start with a board that is a little over twice the width that is required.  I then cut the dadoes across the width of the entire board and then rip them to width. 

Since the dadoes are cut at the same time the left and right are guaranteed to meet.

But lately I am using dowels as they are structurally much stronger than a dadoed joint.

[Pirate]

This is where a ras shines,
If your ras has the capacity, you can cut dados in both sides at the same time.
For this job a ras is a real time saver, even if you cut 1 side at a time.

[mikefm101]

Maybe you know this, but If you are using “3/4” plywood” it probably isn’t 3/4” thick despite how it might be marked at the store.

If you use a 3/4” router bit or dado blade set up the dado will be too wide.

Mike

[Cooler]

Maybe you know this, but If you are using “3/4” plywood” it probably isn’t 3/4” thick despite how it might be marked at the store.

If you use a 3/4” router bit or dado blade set up the dado will be too wide.  

Mike

They sell "undersized" router bit sets for plywood.  I have a set.

As for dados, I always test fit the dado to the material.  Also note that it is not guaranteed that consecutive sheets of plywood, MDF or particle board bought at Lowes or Home Depot are of uniform thickness. 

I was building some book shelves from white laminated particle board.  I carefully setup the dado blade for a fairly tight fit.  But the second sheet was thicker than the first and it would not fit in the dadoes.  Both sheets were taken off the stack in sequence. 

So check the thickness of all the sheets before cutting the dadoes.