Blind Dado Cabinet Construction

A discussion of dado joints for connecting cabinet sides and backs. February 6, 2007

Question
We currently build all frameless (panel saw, band, line bore), screw assembly with applied finished ends. Bases on levelers (only toe notch finished ends). We are investigating blind dados (nested based on a router) to speed things up and eliminate finished ends. If you completely enclose the backs to help square things up, in other words a stopped dado on cab sides with mating through the dado on the underside of the top and top side of the deck, don't you have to run these dados as a secondary op?

It would seem they are on the opposite side of the tongue your cutting. I assume you don't want to CNC machine both side of a board. Or, is everybody cutting tops and bottoms shallow with a through dado for the back? Then you have to shoot fasteners to hold the back rather than strictly glue and clamp. A 1/4" back with a nailer "snuck in" behind it seems like an assembly nightmare or have you gone with a 3/4 back (on bases). Lastly, as mentioned earlier, we currently build a square (30" box) base and extend (4") and toe notch applied ends only. With a blind dado, do we lose the legs (along with the finished ends) and notch every cab side?

Forum Responses
(Cabinetmaking Forum)
From contributor R:
You are right about having to machine both sides. It is called a 'flip'. We don't build bases we build captured backs to save on flips. The sides are only full dadoed. The deck and top back stretcher are lapped, stapled and a 3/4" nailer applied. The decks of wall cabinets require a flip. We run the deck back to the wall and capture the back on 3 sides. I also use legs on my base cabinets. Just because youre using dados doesn't mean you have to stop using legs.



From contributor H:
I usually use an applied end panel as well, but I also build melamine bookshelves and use my pockethole machine to bore the back on the side of the cabinet that will show and then I insert it into the cabinet from the back. I shoot and screw the sides that don't show and pocket hole the one side or both that do show. I like my upper kitchen cabinets to be full 12" deep, and will cut end gable 5/8 deeper (12 5/8" for uppers). This way I shoot and screw to 1 side top and bottom and then pockethole to the finished end. Its best to have a pneumatic pocketholer with extension table or temporary rollers for long pantries or bookshelves.


From the original questioner:
To contributor R: So, I guess you are using a 1/4 back for uppers and bases and stapling it to the top (upper) and top and bottom (base). I was considering going to a 3/4 back (bases) and drop the nailer. We have an opportunity where we would need to build a series of workstations consisting of 1, 2 or 3 cabs and need a nailer near the top and bottom of the base cab. These would be installed by others so I was hoping to not have any staples showing at all and thought I'd get a more rigid box with an "all glued in" 3/4 back. If you are using legs, are you using full height sides and notching everything? Again, now we only notch finished ends. I appreciate your help!



From contributor R:
When we use legs we use 30 1/5" tall sides, no notching. We run the toe kick cover around the end. If we have a cabinet that the back is exposed we use a 3/4" back dadoed on. The edges are edgebanded and the back is glued on, no fasteners. They are very strong. This back is put on the back of the sides not in between them.


From the original questioner:
I haven't tried pocket holes for assembly. I worry about joint strength if someone other than my guys is handling things! I'll have to give it a chance. I currently have an old Porter Cable pocket cutter. I had been looking into a Kreg.

I had been wondering whether I could "get away" with wrapping the base with toe material rather than run the side to the floor. On your 3/4 back, if I understand, you are notching a rabbitt on the long sides of the back and inserting into the cab so you've got wood to wood glue surface, not just "planting it on." When you band that thin (3/8 lets say) edge are you manually trimming? My bander copy wheels are about 18mm away from the cutters and about 8mm thick (this is why I asked about them dropping into the dados earlier).



From contributor H:
We also turn the corner on our base and we use the Camar adjustable feet. We use Fastcaps instant glue for the mitered return and powergrab to install to floor and under the deck of the base cabinet. You need not worry about the strength of the pocketholes for the backs as I have been doing this for years and my clients have told me that when they move, these cabinets are indestructible. I have built thousands of 8' high melamine bookshelves with 5/8 backs pocketholed all around and my clientele has literally thousands of books.

Ive never had a structural failure in 27 years. This includes library units and bookshelves for major bookstore chains. I have a Detel pneumatic pocketholes borer with foot pedal and an extension table on each side so that 8' panels go real fast. You can set up a fence system with flip stops from Kreg very cheaply to accomplish this or just have markings on a makeshift fence as accuracy is not essential for a back. I also use the same system for 1/2 and 5/8 drawer bottoms in pre-finished ply or melamine.



From contributor R:
This is the CNC world. Many more things are possible. I am talking about a 50% thick tenon sticking out the back end of each side, out the back of the deck and out the back of the rear top stretcher. These fit very nicely into stopped dados machined into the back. They are very strong, as is the glue joint that squares the box.

In this case this can be an end cabinet, the side and back are finished; the edgebanding goes on the end of the back 3/4" thick. Looking at the back of the cabinet you see a nice veneer, looking at the side you see a joint 3/4" wide in the veneer. (The side piece and the edgebanded end of the back). Its way stronger and cleaner than a rabbited joint.