What method for bookshelf dadoes?

[Aaron Wingert]

I'm going to be building some 8' tall built-in bookcases, using 3/4" birch plywood for the carcase and poplar faceframes and shelf nosings. All but one shelf on each case will be adjustable.

I'll have 14" x 7'-6" tall sides, and need to cut dadoes horizontally in them to receive the fixed shelves (for TV and equipment) for a strong joint. Also need to dado in the top and bottom shelves. I'm nervous to do it on the tablesaw because I lack the outfeed support on the sides of the saw and am worried about being able to keep the cuts straight given the minimal fence contact. So I'm thinking the router might be the way to go. I could clamp a straight edge and follow it, but am thinking that a guide bushing in a template might work...Perhaps a t-square setup that has a slot so I can use a 3/8" or 1/2" spiral bit to rout the full width of the dado without adjusting the template.

Any ideas? I'm curious how you guys do this.

[Dewey Torres]

I use one like this:

http://www.woodmagazine.com/woodworking-plans/routing/exact-width-dado-jig/

You are right about one thing. I don't recommend trying this on the table saw.

[Tom Davis]

I use a jig similar to the one Dewey suggested. I cut the dado's in an oversized panel thd then rip it into 2 "bookmatched sides".

Tom

[Chris Padilla]

I use one like this:

http://www.woodmagazine.com/woodworking-plans/routing/exact-width-dado-jig/

You are right about one thing. I don't recommend trying this on the table saw.

That one works well but be darn tootin' sure your plywood is the same thickness all the way. I got some A-1 that wasn't...sure upset my wagon. :(

There are also "plywood bits" out there that cut 23/32" (for 3/4" plywood) and 15/32" (for 1/2" plywood) and even 17/64" (for 1/4" plywood) but even these dimensions aren't something you can count on these days so and adjustable guide like the one Dewey shows will work the best.

[Dewey Torres]

I got some A-1 that wasn't...sure upset my wagon. :(

Well I don't guess you were able to cope or caulk that one but I would be willing to bet you cussed. Don't ask me how I know:rolleyes:.

[Doug Shepard]

I'm going to ask a dumb question only because a friend of my uncle's did this once. His ceiling fit 8 ft shelf units, but not his doorways so when he went to move them inside, they had to be carried longways then tipped up. You guessed it - not enough height to swing it up. So how tall are your doorways? If you have to make upper/lower sections it might make TS dados more practical, so thought I'd ask.

[Peter Quinn]

Leave the plywood at 30" width, use the TS and dado with an adjustable saw horse for outboard support or a sled if your rails don't give you enough reach on the fence, and rip the 14" sides out of that. Otherwise a router with a straight clamping guide, shop made or purchased, works well though a bit dustier and noisier. Still leave the material at 30" or so, route both at once and rip to width.

Make sure to rip all factory edges off your shelf material, lose at least 1/2" but preferably 1" from each factory edge, try to make all from the same sheet, and check their thickness with dial calipers. I got a single sheet of A-1 pre finished last spring that varied by as much as .025" over its length, tough to use a TS dado to match that.! If you wind up with varying thicknesses of plywood, search the creek for a post by Glenn Bradley on his adjustable router dado jig. Its easy to build, works great, matches the thickness of the actual material for each shelf perfectly, and his pictorial explanation of its construction is worthy of a magazine article!

[Gene Michael]

I've had some issues with tear out when using router bits on veneered plywood. As an alternative, consider using a radial arm saw with a high quality dado blade. If you don't have a RAS and will have to go with a router, be sure to use a high quality bit.

[Von Bickley]

I would use the router. I would clamp my two side pieces side-by-side and then use two straight edges clamped to the side pieces. The router would ride between the two straight edges and keep the router from wandering off course. If the side pieces are clamped side-by-side, your dados will line up for a perfect match. :)

[Aaron Wingert]

Dewey's jig is exactly the concept I had in my head, only better! Thanks for posting that!

I have to say that I like the idea of mounting a dado blade in a radial arm saw. I don't have the saw just yet, but am thinking of picking up a used one. Can a dado be mounted in most brands, just like tablesaws?

[Karl Brogger]

I'd use the tablesaw. Pull it backwards across the dado stack to score it, then run it full depth the correct way.

[John Thompson]

I use a router to cut dadoes. A simple T square jig from two pieces of adjoined ply in the shape of a T. You run the router on the long piece which is the fence whiich will produce a dado in the short T piece. Once that is done.. your T becomes a fence you can clamp down after you align the cut dado in the T to your marks on the real deal.

Almost fool-proof.. quick and the jig is cheap and can be built in thirty minutes. Once you have it you can use it forever. I did a simple shoe rack the other day with 5 matching stopped dadoes. Took about 30 minutes to cut all 10 as I was in no hurry with such a short project as the shoe rack..

Good luck...

Sarge..

[Jim Kountz]

I'd use the tablesaw. Pull it backwards across the dado stack to score it, then run it full depth the correct way.

Holy cow Karl tell me you were kidding!! You actually run something backwards across your table saw?? Maybe its just me but that sounds like a trip to the emergency room just waitin to happen.

[Steve Rozmiarek]

Talk to a friend with a sliding tablesaw? Router would be my plan B.

[John Thompson]

Just in case you don't what a dado T jig is Aaron.. I needed a new one with a wider fence to get more clamping room than my old one. From my last post 35 miinutes ago.. I went down and built a new one... groved the dado in the T and set up for a dado. Then took two pictures and will post.

Again.. simple to build.. easy to set up... best to draw the lines out on the stock to be cut in lieu of using one mark.That avoids setting up on the wrong side of the line you drew.. And as others mentioned best to butt the board together to assure the same tick mark on both boards but with this method cut one at a time as it is almost fool-proof once set up.

Sarge..

[Jim Kountz]

John are you a lefty? Just curious!

[John Thompson]

John are you a lefty? Just curious!

Nope... I prefer to place the router base on the fence on the side that allows me to pull the base toward the fence in lieu of keeping it pushed to the fence, Jim. And my 5.5 portable shop vac used for dust hook up is forward of the twin screw vise. I prefer it to be on the opposite side of where I stand with the electrical cord draped over my shoulder to keep those out of my way.

BTW... there is a dado groove on both sides of the T but you can't see the other side for the clamp. That set-up is done with a not too wide board and the left to right pull is no balance problem. But.. if it were a wide panel I would cut in from the twin screw end so as to be centered on the work-piece for better balance.

In essense... just depends on the given situation as to how I approach it. Any further questions or comments... ask and I will answer tomorrow as I have been in the shop since around noon.

Regards...

Sarge..

[Karl Brogger]

Holy cow Karl tell me you were kidding!! You actually run something backwards across your table saw?? Maybe its just me but that sounds like a trip to the emergency room just waitin to happen.


All my cabinets are plywood boxs. Almost every dado that is seen gets scored by running it backwards across the head. Dead serious. I learned that from the cut out guys at a shop I used to work at. Its hairy at first, but once you get used to doing it, its easy. You're going only about the depth of the veneer, or less. You just keep it tight to the fence and let the head push it back. Just about the only time I don't do it is when I've got a long, skinny piece and a dado in the middle. Then I just go slowly forward.

The trick to keeping parts straight while dadoing them on the saw is to keep them moving. When you stop all that friction is hard to overcome equally.

[Aaron Wingert]

A little followup here...

Today I cut up some poplar and made a jig like the one John describes. Very easy to make, and equally easy to use. It makes very clean and perfect fitting dadoes with my 1/2" spiral bit. Version one is a challenge to clamp since it is rather narrow, so version two will be made from much wider boards or baltic birch plywood when I have some cutoffs. Version one will suffice for now!

Thanks to all of you guys for your insight. I appreciate it very much.

[Joe Scharle]

A little followup here...

Today I cut up some poplar and made a jig like the one John describes. Very easy to make, and equally easy to use. It makes very clean and perfect fitting dadoes with my 1/2" spiral bit. Version one is a challenge to clamp since it is rather narrow, so version two will be made from much wider boards or baltic birch plywood when I have some cutoffs. Version one will suffice for now!

Thanks to all of you guys for your insight. I appreciate it very much.

I have a couple (different routers) of these from Shopnotes. This type has a built in clamp. Spiral bits have changed the way I cut dados and tenons. I can cut a bunch of dados wih a router faster than I can fiddle with a dado stack. Using a 3/8 bit, I really don't care what the current ply thickness is, as it seems to vary from stack to stack.

http://www.ncwoodworker.net/pp/data/194/Rabbet1.JPG