Stock dimension question

[Bill Morgan]

I am beginning a small bookshelf project with some cherry I acquired. The boards are already at 3/4" thickness, but obviously not flat. So this is where my question arises. My final stock thickness will end up at 5/8". Specifically, is this acceptable for a small bookcase(36" L x 24" H) with one shelf in middle. And overall, what determines stock thickness in projects? Thanks in advance for your insights.
Bill

[Jamie Buxton]

There are sag calculators on the web. Google "sagulator".

[Dan Forman]

That seems a little thin to me, given that books are one of the heaviest things one can store. Not saying it can't be done, hopefully someone with more experience than I will weigh in.

I wouldn't get lumber any thinner than 15/16" for the very reason you are bringing up. It will likely need further milling, and for most purposes one would want to arrive at at least 3/4" finished thickness after milling, at least things larger than decorative boxes or drawers.

Dan

[Chip Lindley]

You've discovered the downside of pre-planed hardwood. Much 3/4" stock is unusable because of cup and warp after surfacing. Such a waste!

4/4 rough stock starts out at about 1-1/8"--plenty of thickness for jointing and planing to a final thickness, anywhere from 7/8" to 3/4". Often times thicker stock is desirable for bookcase shelves. Why plane thinner when strength and stiffness suffers?

[glenn bradley]

I agree that over a 36" span, supporting books, even 3/4" seems thin. I would consider designing in a rabbeted front rail for support that would add appearance value as well as additional sag resistance.