To dado or not to dado

[Christiaan]

Hi there 

I am new to this site. I am starting out my furniture design company and my first project is building a side table. 

It is very basic design made with only 3 panels. The question I have is should I dado cut joining grooves or will a flush 

joint be strong enough. ideally I do not want to use screws especially for the top joint. I recently purchased a Bosch plunge

router and I do not have a table saw only a circular saw. If this is going to be a recurring build then I would like a setup 

that can be easily setup each time. In the image below you will see the design, you will notice that I have metal bracket 

on the ends of the joints. This is only for aesthetic purposes and I do not think they will be strong enough to carry load. 

To save space and time I get the panels pre cut and my timber shop and I only do the assembly in my garage.  Timber used

is 27mm birch plywood. 

Another thought is to use an angled dowel or screw joint jig like the one in the image below. 

All of my designs has clean straight joints and normally has a piece of sheetmetal,  so I am trying to produce furniture 

that is easily assembled by myself to reduce manufacturing cost. 

Thanks and will appreciate the input. 

 

Edited July 29, 2018 by Christiaan
additional information

[ChrisK]

Welcome to the forums dude.

 

Butt joints are the weakest joints. If you are going to join to pieces of plywood then yes, I would dado but I would also use some form of fastener, be it a floating tenon, screw etc. In looking at you rendering it appears that there is no support for the majority of the table so would the metal triangles offer any support? Also, with pocket hole screws there will be an obvious hole left by the pocket which can be filled and blended but the screw itself really does not offer any structural integrity on its own when used in plywood unless there are sides and a shelf or top. Hope this helps, Chris

[SetBuilder]

Look like the majority of the support is coming from the bracket. I would dado it, just mount your router in a table and make a fence for it. Since you don't have a Table saw, that would probably be the quickest way to produce them with the same results.

[khariV]

Dados are great for providing shear support, but they really aren't going to provide much support at all for tension stress, which I think is going to be the primary stress your design is going to see. (Tension stress is pulling apart stress, which is going to happen at the joints when a load is placed on the end of the cantilevered tabletop).  Dados will help keep the vertical piece in place, so my vote is going to be for using them.

 

As SetBuilder said, the brackets are going to be providing the vast majority of the reinforcement for the tension stress.  These probably need to be pretty beefy or the table will flex and potentially collapse when someone puts more than a cup of coffee on it.  If you're considering having the brackets made for you, you could probably go with a heavier gauge steel to provide the necessary support.

[SetBuilder]

Another option, since you plan on using 27mm plywood do you plan on edge banding it?  If you are then you can use two layers of 18mm plywood, make the top in one piece and the second layer in two pieces giving you the dado, then edge band. It would be a little thicker but a quicker build.

[BMack37]

If you make the bottom flat piece out of two pieces you could use as many screws as will fit to hold the vertical piece to the bottom piece because you'd be covering that with the back piece. Fasten that with through screws then put a plug in the holes to hide them and the vertical piece shouldn't go anywhere. The top piece doesn't need to hold as much weight so there are plenty of other options.

[Jronman]

That is a nice design. Maybe you can screw from the bottom into the vertical piece without seeing any screws. It would add a bit more strength but I would not trust the joint for much load due to the top being cantilevered. I would agree with the others that larger more beefy brackets would be a good idea.