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Re: self drilling screw spacing for light gage

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The  "Cold-Formed Steel Design Manual", 1996 edition, published by
the American Iron and Steel Institute.  Section E4, starting on page V-93
deals with screw fasteners.  

E4.1 states the requirements for minimum center to center spacing, 
and states:

		"The distance between the centers of fasteners 
		shall not be less than 3d".  

"d" is defined as the nominal diameter of the fastener.  
Listed below are typical nominal diameters of fasteners:

	Screw Size		Nominal
				Diameter
				(in)

	#10:			.190
	#12			.210
	1/4"			.250


E4.2 deals with the requirements for "minimum edge and end 
distances", and states:

		"The distance from the center of a fastener to 
		the edge of any part shall not be less than 3d.
		If the connection is subjected to shear force
		in one direction only, the minimum edge 
		distance shall be 1.5d in the direction 
		perpendicular to the force."

Note that a reduction in end distance (in the direction of the
force) is NOT acceptable.

There is nothing I know of that in some way officially
sanctions the reduction of the center to center screw 
spacing below 3d.  

The issue of screw spacings below 3d has been discussed 
during meetings of the "Truss Subcommittee" of the 
"Committee on Framing Standards", which operates under 
the auspices of the American Iron and Steel Institute. 
The "Truss Subcommittee" is developing a document called 
the "National Design Standard for Cold Formed Steel Trusses".  
This committee meets again June 25 at the Moscone Center in 
San Francisco, in conjunction with the PCBC show.

Contact AISI for more information about the activities
of the "Committe on Framing Standards", or visit their
website at:

 		www.steel.org/construction/framing/


Brad Cameron, P.E.
Keymark Engineering
Boulder, Colorado 80301
Phone:	303 443 8033
Fax:	303 443 2196

----------
> From: Seaintonln(--nospam--at)aol.com
> To: seaint(--nospam--at)seaint.org
> Subject: Re: self drilling screw spacing for light gage
> Date: Wednesday, June 09, 1999 5:09 PM
> 
> Dan, 
> Larry Williams (director of LGSEA) may be able to help you on this one.
He 
> can be reached at lgsea(--nospam--at)aol.com. At worst case, he should be able to lead
you 
> to the sourse of an answer. 
> Dennis
> 
> In a message dated 6/9/99 9:09:04 AM Pacific Daylight Time, 
> dan(--nospam--at)willettengineering.com writes:
> 
> << I have run into an interesting problem.  That being the difficulty in
>  finding information on minimum spacing and edge distances of screws for
>  connecting light gage members (web to chord connections in light gage
>  trusses, specifically).  The particular screw that has been used is a
12-14
>  TEK3 as manufactured by Triangle Fastener Corp. under the trade name
>  "Blazer".  A call to TFC was of no help whatsoever.  I then tried the
Hilti catalog under the assumption that a similar screw by different
>  manufacturers
>  would, in essence, be indentical.  Unfortunately, Hilti does not provide
>  this information in their catalog either (at least for their "Kwik-Pro"
>  fasteners).
>  
>  I had some info at one time calling for 3/4" minimum spacing and that is
>  what was specified.  I have since misplaced it.  The problem is that my
>  trussess were assembled with screw spacing of 1/2" or even slightly
less.  I
>  would like a firm number on minimum spacing as well as a formula or
table
>  that will allow me to decrease the allowable load per screw based on
some
>  spacing less than the minimum.  If anyone has this information, or can
point
>  me in the proper direction on how to obtain it, please let me know.
>  
>  thanks
>  Dan
>  
>  Sherman D. (Dan) Vines
>  Willett Engineering Co., Inc.
>  dan(--nospam--at)willettengineering.com >>
>