Design help

[FS7]

I am finally replacing my 20 year old Target particle board nightstands with something new and durable. They've been through a lot of abuse. But I want something more bed level (not 8 inches below, as they are now) and much more durable (I will use the ceramic finish, as I've been happy with my desk).

Now, what I would like to do is an "open shelf" just under the top, something like this (not the design, just the open shelf):
My design will be more traditional, like a typical Shaker or Mission, but I think for a clean look based on how I use it a top shelf would be helpful. The Shaker designs I see online have open storage on the bottom. Top is a bit more challenging.

My question is how would I best design this so that I can attach the top? It will be a zebrawood top (they're already done) with a mostly walnut cabinet. I normally screw the tops in from underneath. If the open shelf is about 6" or something like that (I haven't decided yet) that doesn't leave a whole lot of room for screwing the top in. I could try an extension with a right angle drill attachment, which I don't have but are not expensive. I worry they will have enough torque, but maybe they do. Otherwise, I don't see a way to easily attach the top. Any thoughts?

[Willyou]

I am currently finishing up a chest of drawers with upper drawers only about 6" deep. As you said, this doesn't leave enough room for a power tool. I screwed the top of the chest down with square drive Kreg screws using a 1/4" drive ratchet wrench. It worked just fine. Torx screws might have worked even better.

[Dave Crow]

I like these, use hex head screws when the space is limited.

https://www.leevalley.com/en-ca/shop/har...em=13K0101

[iclark]

You could cut a tongue (as in tongue and groove) on the top edge of the sides and back.

Cut matching blind dadoes on the underside of the top and just glue it on.

Depending on the relative grain orientations, you might only want glue on the side joints.

If you want to be fancier, you could do blind sliding dovetails for the sides and rabbet the top for the back.

[FS7]

I was wondering about a ratchet with my standard Kreg screws. Getting them started is probably the hard part, but I think I could make that work. I would probably have the same issue with those tabletop mounting clips (I have a bunch of those handy already, figure 8 or otherwise). The same problem exists with getting the screws in there and a tool.

Tongue and groove would work, though it would be somewhat challenging to both cut blind dadoes in the top and have them perfectly aligned. Similarly, sliding dovetails would be super fancy, but also challenging. I think cutting them in the top of the carcass (especially because I'm planning on doing 1.5" square legs with plywood panels in between) would be almost impossible, unless they were one-sided.

Another idea I had was the Festool knockdown connectors, which are pretty awesome, but again cutting for them might be pretty challenging. It's also an expensive solution for what they cost and not as easy as it should be.

I think I'll probably go with plain old screws.

[Willyou]

I was wondering about a ratchet with my standard Kreg screws. Getting them started is probably the hard part, but I think I could make that work. I would probably have the same issue with those tabletop mounting clips (I have a bunch of those handy already, figure 8 or otherwise). The same problem exists with getting the screws in there and a tool.

Tongue and groove would work, though it would be somewhat challenging to both cut blind dadoes in the top and have them perfectly aligned. Similarly, sliding dovetails would be super fancy, but also challenging. I think cutting them in the top of the carcass (especially because I'm planning on doing 1.5" square legs with plywood panels in between) would be almost impossible, unless they were one-sided.

Another idea I had was the Festool knockdown connectors, which are pretty awesome, but again cutting for them might be pretty challenging. It's also an expensive solution for what they cost and not as easy as it should be.

I think I'll probably go with plain old screws.

The Kreg screws I used are self tapping. It requires some pressure to get them started, but once they take a bite, they go right in (wood is cherry). Yes. You will have the same issues with the clips, but it is doable and another good solution.
If you are able to pre-drill, this would make it easier. Be sure to carefully mark or make some alignment blocks so you can get the top back into the same place after removing it for pre-drilling.
Be very careful with dadoes and glue. You have expansion/contraction issues to accommodate. Screws are better. Just make sure the holes are elongated (cross grain) to allow for movement.

[Bill Holt]

I'm a big fan of the figure eight clips.  I would mortise the sides for the clips, lay top on, mark the top from underneath, then predrill for the screw.  The figure eight clips are forgiving and predrilling makes starting a screw easy.  A ratchet and a square drive screw should do the job.

[MstrCarpenter]

I'm assuming it's solid stock (if not disregard) Although they're different species, you do not have a cross grain situation. 3/8" diameter dowels spaced 4" or so apart will hold it together just fine. As an introduction to Cabinetmaking, the students project is/was a simple mahogany bookcase. Bottom and center shelves fit into stop dadoes in the sides, top attached with 3 dowels each side, and a recessed 1/4" plywood back nailed on. (We did get to choose from several options for the the base detail.) I made mine over 50 years ago. Still solid as rock despite having been lifted many times by the top while full of books.

I learned a lot on that project that is still useful on most of my projects. Like shifting pipe clamps slightly off of parallel to square up the case during glue-up. Dowel centers are so simple and foolproof. Making drill bit depth stops by drilling the end grain of a stick then cutting to length is better than "store bought" ones with a set-screw. The base front can be glued to the bottom shelf and the base end miters, but the ends get attached with panhead screws in short slots due to cross grain.

[Gary G™]

I make my own wood “buttons” for attaching tops.
They might work in your application—not sure.

[iublue]

I suggest doing some research on the different expansion rates between the two different woods.

Locking them together by simply screwing them together could lead to problems down the road. 

Do you have a moisture meter?

Walnut has a Tangential % of 5.5% and a Radial % of 7.8%  Whereas Zebrawood has a T% of 8.8% and R% of 11%.  So the Tangential value of Zebrawood is 50% higher than Walnut and the Radial value is over 40% higher.

A cracking problem is not assured but IMO, it is also not out of the realm of possibilities.