A rabbet is "half" a dado or groove done on an edge...I've never heard of usining mortise and tenon joints for a shelf, unless there is a front and back support rail...So that leaves you with a through sliding dove tail, stopped sliding dove tail, through dado, stopped dado, through tonque and groove, or stopped tonque and groove.
The through dado would certainly be the easiest but, if the carcass is not face framed I would recommend the stopped dado. FWIW.
I build a lot of cabinets using a full-width dado. Some people find it easier to get a tight fit with a narrower dado and a rabbet or tongue milled into the shelf end (a slightly sloppy fit in the dado gets covered by the remaining shelf material). Personally, I take the time to get a tight fitting dado instead of taking the time to do the extra milling on the shelf---different strokes, I guess.
>Also, I plan on making the dado 3/8" deep.
I make my dadoes 1/4" deep for two reasons:
1. more remaining strength in the vertical piece.
2. less material to remove, so less strain for the router and bit I use to cut the dadoes. (I cut 1/4" deep dadoes in a single pass. 3/8" is a bit much in a single pass, IMHO)
You need to learn from other people's mistakes. You'll never have enough time to make them all yourself.
I disagree with you on the dado depth, 1/2 the thickness is the generally accepted and practiced spec. Your theory that the verticle member is weakend by the normal method doesn't hold water; the shelf in the dado makes up for the loss. Your method actually increases the potential for the joint to fail because the "shoulders" are not wide enough. This would be of particular concern where a heavy load such as books or TV would be placed on the self.
IMHO, the argument for "less strain" on the router is equally as weak. Normal procedure is to take multiple passes any way, even if you have a monster 3hp router. Dados done on the TS are far more efficient, especially in a professional shop.
While I don't doubt that you have never experienced a failure, I would say you have been lucky. FWIW, I owned my own cabinet shop for close to 15 years and still take on cabinet work...
To say that using a TS is a superior method for ploughing could be very misleading, IMHO. Personally, I use a frame under which the material is clamped, on a dedicated table, and routinely remove 5/16 to 3/8 of plywood in a single pass with a modest router. (If I'm removing material from something which requires a very clean cut, I'll simply cut my first pass at veneer depth and set the plunge to the overall depth for my second pass.) I've found that having a dedicated dado station is well worth the time, energy and money it takes to build one -- mine can plough up to 36" W and it's a dead 90 degrees. It's especially handy when you're cutting side panels for your F to C's.
For rabbets, however, I stick primarily with the dado blade on the TS with a sacrificial fence set-up.
Norm has a book "Classics from the NYW" that has his cherry-veneer plywood entertainment center with a very thorough description of how to build it. It's a great book, and I highly recommend it. If you happen to be building one of the projects in the book, that's a great excuse to buy it!
I got lucky and was able to tape the episode where he built it - between the book and the tape, there's a lot of instruction. As soon as I get the $$$ for the wood, I'm going to take a stab at it.
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