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Fastening Tips for the Contractor

Correctly installed fasteners produce a secure connection

Triangle  Jun 4

Engineering professionals specify a variety of fasteners for metal building and roofing applications based on many critical factors. When properly installed, professionals have confidence that the connection meets the requirements of the overall system.

Because the installation plays a major factor as to how well the fastener performs, it is important to use care during installation and follow a few basic techniques that will contribute to producing a secured connection.

The most popular fasteners used for attaching sheeting to steel substrates are self-drilling screws designed to drill and tap steel in a single operation. They are available in a wide variety of diameters, lengths and materials.

The following tips will assist you in selecting the correct type and help you get the best performance.

Screw Types and Lengths

Drill screws are available in various drill point types (sized by a number) that are capable of drilling and tapping various thicknesses of steel. The larger the drill point type (number) for a given diameter, the thicker the steel it will drill and tap. Select a drill point type that meets the drilling thickness capacity of the screw diameter.

The length of the screw is determined by measuring the total distance of the materials being fastened together and adding an additional length so that at least three full threads extend beyond the substrate (referred to as the load-bearing length). This will ensure the full thread engages into the structure, and the screw produces its optimal pullout loads. Select a screw that has a load-bearing length greater than the thickness of the materials being fastened together.

Screws exposed to the weather should be corrosion resistant and perform at least as well as the panel. Contact your fastener supplier for recommendations on the proper fastener that will minimize rusting.

Power Tool Tips

For fasteners to perform to their optimum level, install them according to the supplier’s recommendations. Be sure the appropriate installation techniques and correct tooling are used:

• Screws should be installed using a 2,500-rpm maximum screwgun.
• Use 2,000-rpm or less when installing into 1/4-inch-thick steel or greater.
• The screwgun should include a torque control or depth-sensing feature to minimize damage to the sealing washer and reduce the possibility of over-driving the screw to failure.
• Do not use impact tools for installing drill screws. They can easily exceed the torque strength of the screw, which can cause strip-out and/or screw breakage.

Accessory Tips

Worn-out or inexpensive drive bits and nut-setters can cause poor drilling performance, strip the recess, and damage the paint on the screw. When using hex drive nut-setters, be sure to set the magnet so that the hex head of the screw fully engages into the hex of the drive socket. Using good high-quality accessories will eliminate wobble and improve drilling performance.

Installation Tips

Drill screws perform best when they are installed perpendicular to the surface using medium pressure. This allows the drill point to penetrate the steel without causing excessive heat that can reduce drill times. Be aware that all the drilling must be complete before tapping begins, or damage to the drill point will occur.

Understanding how screws perform and using proper techniques will help install self-drilling screws. Taking care during the selection and installation will produce the expected performance, thereby reducing callbacks and system failures.

Joe Stager is vice president of Triangle Fastener Corp., Cleveland. To learn more, visit www.trianglefastener.com.