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Re: Screw Pullout Values

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Mike & Bill
In my reply to Bill, I forgot to explain that the
Canadian code only covers softwoods. They address end
grain withdrawal by reducing the allowable load for side
grain pull-out by 40% and add a couple of stipulations.
Gary


On 8 Jun 2005 at 8:36, Michael L. Hemstad wrote:

> -----Original Message-----
> From: Gary Hodgson & Associates [mailto:ghodgson(--nospam--at)bellnet.ca] 
> Sent: Tuesday, June 07, 2005 8:31 AM
> To: seaint(--nospam--at)seaint.org
> Subject: Screw Pullout Values
> 
> I'm looking for pullout values for screws in oak parallel to the
> grain.  Does anyone know of any net resources regarding this?
> 
> 
> 
> Gary,
> I designed a small stick-framed building a short time ago, and wanted
> to use lag screws in withdrawal.  I could have gone to the NDS as Bill
> Polhemus suggests, but in my youth I had a number of bad experiences
> with hardware store lag screws repeatedly breaking during
> installation, regardless of pilot holes, thread lubricant, and
> chanting over an incense holder.  Thinking to step up in quality, I
> went to Simpson's catalog and looked at their screws.  Nowhere in
> their catalog do they give a withdrawal value.  Mind you, I'm talking
> about side-grain withdrawal; they feel it's too unpredictable to
> tabulate.
> 
> Needless to say, end grain withdrawal is just that much less
> trustworthy.
> 
> Now, when I'm not worrying about my structures breaking their
> fasteners, I do some woodworking as a hobby.  I just finished a set of
> oak bookshelves where I used sheetrock screws in end grain withdrawal
> to hold the shelves in dadoes in the sides.  Those things took up like
> they were in rock.  In fact, I overdrove one and broke it, but it
> didn't strip (seems to be a theme with me, breaking screws).
> 
> So, I guess my advice would be, use the NDS values with plenty of
> conservatism, and make sure that the installer does everything right:
> pilot holes, thread lubrication (wax, not soap, especially in oak--the
> water drawn to soap will corrode screws in that acidic wood), keeping
> away from checks and splits, and most importantly, don't let them
> overtighten the screws.  You'll want to schedule plenty of inspection
> time.  And, bring your incense holder and chant book.
> 
> FWIW,
> 
> Mike Hemstad, P.E.
> St. Paul, Minnesota
> 
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