Subject: Re: self drilling screw spacing for light gage
Date: Wed, 9 Jun 1999 15:26:47 EDT
>From the AISI Specification:
The distance between the centers of fasteners shall not be less than 3d. 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 reduced to 1.5d in the direction
perpendicular to the force.
(Tests have shown that screw connections loaded in shear will almost always
exhibit edge failure when the distance from the center of the screw to the
free edge is less than three times the diameter of the screw.)
>From the Prescriptive Method, 2nd Edition:
Screws for steel-to-steel connections shall be installed with a minimum edge
distance and center-to-center spacing of 1/2 inch (13 mm) and shall be
self-drilling tapping in compliance with SAE J78. Structural sheathing shall
be attached with min. #8 self drilling tapping screws in compliance with SAE
J78. Screws attaching structural sheathing to steel joists and wall framing
shall have a min. head diameter of 0.292 inch (7 mm) with countersunk heads,
shall be installed with a minimum edge distance of 3/8 inch (9mm).
Hope that helps!