Carcass construction:
I'm thinking 1/2" maple ply for the sides (only a little more than birch and I'm using real maple for the bookshelf fronts - might as well spend the little extra). Any reason not to use 1/2"? It will need to support it's own weight, at worst a 3/4" plywood top and I plan on putting a single shelf for more paperbacks on top (the ceiling prohibits more than one paperback high on the top).
I'll make dadoes on the inside of the side pieces to hide the plies of the bottom, top and back pieces. The top and back pieces are likely to be flush to edges of the side pieces, but I plan to have the dado for the bottom piece upward a bit from the bottom edge of the side pieces in order to provide some skirting to give the casters some obfuscatory ability. (Ever since Jim wrote obscotulate I've wanted to use obfuscate - it's his fault!
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In addition to glue, I am going to use some symmetrically placed finishing screws - this is going to be the biggest project I will have done, and I don't want my clamping ability to be a major oops factor. The screws are black, 1 5/8" long and take a #1 square drive.
I am going to use 1 1/2" plywood (probably just an exterior grade - picking up some construction leftovers from a friend tonight) for the bottom. I plan on laminating to acheive this, so that I can use 1 1/4" lag bolts for the casters with no protrusion. Maybe I can make little decorative v's with the finishing screws here.
How do I pull the shelf units in and out?
My original plan was to use immovable casters on the bottom of each shelf unit to ride on the bottom panel of the bookcase, with the frontmost part of each shelf supported by a swivel caster on the floor. I would need to have the bottom panel either shorter than the depth of the carcass or make cutouts to accomodate these front casters. I will look into drawer slides for this purpose. I will need to use top / bottom mount slides though, as I don't think I have the clearance for side mount.
Side mount drawer slide analysis:
I could cut an inset into the top and bottom of each shelf unit, that will have no effect on overall width. Using 1/2" ply for the sides gives me 30.5" overall width. Assuming drawer slides are 1/4" thick for side mounts That takes up the 1/4" allowance between the outer shelves and the carcass sides. That leaves me an extra 1" to play with for the two spaces between outer and inner shelves, combined with the 1/4" current allowance, this gives 3/4" for each such space, meaning I'd need to use 1/4" material to support the slides? No, I think that side mount drawer slides are out - I'm already close to my ability limit to meet tolerances already.
Speaking of dadoes, do I use the stacked dado set on the RAS in rip mode or the router with the EZ Smart (or, I suppose, the router in the table)? If router, should I invest in some plywood actual size bits or are my existing nominal size bits (i.e. 1/2", 3/4" instead of the 15/32" and 23/32") acceptable? I could make two passes with an undersize bit, but this idea makes me think that there is twice the chance for error.
The shelf units:
I still need to figure out the height of the shelf units and the distribution of tall to normal height paperback capacity. I need to decide how to pull the shelf units in and out first though.
I'm going to use maple (hardwood, not plywood) for the faces and probably construction grade for the backs, which will live inside of the carcass. If I can find 9.5" shelf melamine prepainted on all sides I'll probably use that. Otherwise, maybe I'll try my hand at edge banding some reasonably good looking plywood with some maple strips - likely to be again construction grade here, maybe just 1/2", since I'm going to run some 1/4" ply (luan or that floor underlayment stuff) down the center of each shelf. I'll maybe put a 1/8" deep 1/4" wide dado down the middle of each shelf top and bottom to help align the luan dividers. This means I'll need to remember to add 1/4" to the height of each shelf divider.
Finishing:
Gah! This project is going to be huge! I don't know that my usual wipe on Bush Oil is the answer here. Maybe I could spray it? I'll need to buy a sprayer... Is there a good HF sprayer? I'd like to run it off my compressor - I have the smaller of the large stand up Husky units, I think it is a 60 gallon tank, in the shop proper. Maybe this will be assembled in the basement and brought up to the shop for finishing. Zounds, what am I getting myself into with this?!