personably as a professionable carpenter who also happens to have a degree in engineering(materials science)(dont ask) screws into wood have a very unpredictable behaviour.
screws (or nains) exhibit very strange behavoir depending on a lot of variables
moiture content , temperature and unlike most materials, distant from the nearest end or crosscut
that is a variable that is imposible to quantify
advice? go with your instincts, trees are a natural product.
If two nails are not enough then put another, 15 nails will not work
add plenty of a constrution adhesive, “no more nails” is a favorite of mine
Replies
BTW, this spreadsheet is for steel on steel machine threads.
-- J.S.
Off the top of my head the # in the ss look about right. I've trusted Mach Hdbk for decades, and their tables correspond pretty well with corporate studies at my desk job.
Recall my old High school classes even taught about inclined plane mechanical advantages -- fine threads = lotsa push for the torque if little friction.