I’m installing a bookcase in a sort of cove in my living room that is exactly 3ft. wide. I’m using 3/4 plywood for the carcass and was planning on using the same to construct the adjustable shelves, but I’m afraid the span is too wide. Do any of you have a good rule of thumb for deciding how wide you can make a shelf with a certain thickness of wood?
Any crafty ideas on beefing up a shelf without making the shelves extraordinarily thick?
Replies
you can try testing it by getting a scrap and cutting it at the widest you would have it, stack some books or weights on it until it bends, then progressively rip the board smaller and smaller
There's enough youth in this world, how 'bout a fountain of SMART??!!
See the Sagulator: http://www.woodbin.com/calcs/sagulator.htm
Attaching a hardwood strip, about 3/4" thick and 1-1/2" tall, at the front and/or back of the shelf will help quite a bit.
-Steve
A good quality ply should be good enough at 3/4. I have built-ins I installed about 25 years ago, with 3 bays about 30" wide each. The shelves are 3/4 maple ply, as are the uprights. I faced them with maple, and used 1/8 ply at the back, nailed to shelves and uprights. The nails should have a head big enough to prevent blowing through the thin ply, or staples will do. The backing is really important for strength, as books are very heavy. I haven't had any separation or sagging, and the shelves have been packed for all of that time with some hefty tomes, as books were the tools of my trade. If you're still worried about the span you could have a central upright, or you could reduce the span to 30" and use some moulding at either side.
Edit. I'd avoid adjustable shelves. Books come in stock sizes, and once the case is built you'll probably never adjust them anyway. That's assuming you use a bookcase for books %).
Jim
Edited 4/7/2008 6:47 pm ET by Jimurock
If you are going to use shelf pins, try putting a row of holes in the middle of the back. I always do this and put a 1 1/2" trim board on wide shelves. That pin in the back supports a lot more than you would think. Make sure you use the same point of orientation to route your vertical holes just like the sides. I have even used two rows, but that was on 4' shelves.
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