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Lee Michaels[_3_] Lee Michaels[_3_] is offline
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Default Shear strength of screws



"Gramp's shop" wrote in message
...
I've always taken a serendipity view of screw gauge when doing rough stuff
as in "hey, I'd better use a bigger screw for this." I need to cobble
together some two bys for a frame for a basement storage rack. I've got a
box of number 9 2 1/2 inchers that ought to do the trick.

Question: Is there a formula for determining the minimum gauge for a screw
if you know the load?


I never thought about it. Just that so many screws today are absolute crap.
If you shear off a screw while driving it into the wood, it is a bad sign.
And it depends where you buy them too. I have had terrible luck with deck
screws and lag screws from the local home depot. But the local ace hardware
store gave me screws that were higher in quality, stronger and a few cents
cheaper too.

If I got any kind of basic repair outside or in the garage these days, I
just use their deck screws. It ain't art or furniture. But it is strong.
They don't shear off and they don't rust outside.

The old standby rule about strength for fasteners is to estimate how many
will do the job. Then put twice as many in there. I have always been
accused of using too many screws anyway.