See Chapter 7.
http://www.fpl.fs.fed.us/documnts/fp.../fplgtr113.htm

David Merrill

"Eigenvector" wrote in message
. ..
In general when joining wood, how deep should the fasterners go? To
clarify, if I'm joining two 1/2" planks with screws - should I use a 1"
screw, a 3/4", 5/8". I'm trying to determine what size screws to order
for
my next project, and to do that I'll need to figure out how deep the
screws
should go into the wood. Seems like in the above example 1" screws would
be
too long, the risk of the point erupting from the wood is too great. But
5/8" is pretty darn short - barely penetrating the second board.

So, it seems like the answer is easy - 3/4". But before I go and ruin a
perfectly nice project, I figure I'd better ask just in case.