Fasteners ensure the job gets done right
Metal builders and roofing contractors have a much better selection of fasteners compared to just a few years ago. With the variety of fasteners on the market, there are many time-saving opportunities ensuring the contractor gets the job done right.
Self-drilling screws
Self-drilling screws, such as Kansas City, Mo.- based Dynamic Fastener brand screws, are used for stitching and sheet-to-structural applications. The fasteners have taller, stout hex heads which create better engagement with the socket facilitating a more efficient drilling operation. To determine the correct self-drilling point, the contractor must first identify the total thickness of material being fastened. The length of the drill bit on the fastener will determine the drilling capacity of the screw.
For instance, a T-1 is used for sheet-to-sheet stitching with a total steel thickness of 0.024 to 0.095 inches. T-3, or purlin screw, is used for a total steel thickness of 0.036 to 0.21 inches. T-4s are used for a drilling capacity of 0.125 to 0.375 inches. T-5s have a drilling capacity of 0.25 to 0.5 inches.
Recently, Dynamic Fastener introduced the Fenderhead #14 diameter stout T-5 with 5/8-inch drill capacity. The giant washer face measures 5/8-inch outside diameter (OD), provides pull over values and creates more than 100 percent additional bearing area compared to the common 7/16-inch OD washer face. Due to the 5/8-inch washer face, some contractors have used this screw for decking in lieu of burning 5/8-inch puddle welds. This eliminates the hassle of repairing weld burn-throughs and simplifies the inspection process.
The correct screw gun
When installing self-drilling screws, it is critical to use the correct screw gun. A 2,500-RPM screw gun is required for T-1 and T-3’s. A 1,000-RPM screw gun is recommended for T-4 and T-5 screws. When drilling through 1/4-inch or thicker steel it is very important to use a slow RPM/high torque screw gun. The DeWalt 269 with 1,000 RPM is a suitable tool. If you use the very common 2,500-RPM screw gun (DW268) or 2,000-RPM screw gun (DW267) to drill into 1/4-inch or thicker steel, you will prematurely burn up the motor in the screw gun. Plus, you will burn up the points of your screws at an unacceptably high rate. Everyone knows there is a direct tradeoff between high speed and high torque. When drilling thick steel, high torque is what you need.
Self-drilling screws are available in #6-5/16-inch diameter, from 3/8-inch to 10 inches long, with or without a sealing washer. They are available with a hex, Phillips and torx head. The low profile head is excellent for standing seam clips or architectural clips to steel.
Self-tapping fasteners
Self-tapping fasteners are recognized in the metal building industry as Type A, B or AB. The Type A fasteners, which have a coarse thread and a sharp point, are commonly used as side over lap
(stitch) fasteners and flashing fasteners for metal cladding. They are also used as structural fasteners to attach cladding to sub-girt framing whose thickness is 18-gauge, or lighter steel or into wood.
The B fasteners, which have a fine thread and a blunt point, are used primarily to secure cladding to heavier building structural members whose steel thickness is 16-gauge to 1/2-inch. The Type AB fastener has a similar thread as the Type B screw, but its point angle is the same as the Type A. All three tapping screws require a pre-drilled hole before installation, unless going into very thin or soft materials. Panel and structural thickness will determine the correct drill bit.
Coatings
Dyna-Coat is an organic polymer coating designed to provide corrosion resistance for metal fasteners. Fasteners coated with Dyna-Coat exhibit resistance to marring, chipping and abrasion. These coated fasteners also have strong resistance against acid and alkaline chemicals. Dyna-Coat passes the 1,000-hour salt spray test. The color of the coated fastener is metallic silver.
When a fastener is required for a highly corrosive environment there are a few options to consider. Bi-metal screws consist of a 300 series stainless steel head and body which is fused to a carbon steel body/drill tip. This will eliminate the need to pre-drill. There are 410 stainless steel screws available with a Dyna-Coat 1,000-hour salt spray premium coating. Stainless cap heads is a unique design that incorporates a 300 series stainless cap mechanically formed around a high-strength carbon steel fastener. A Zamak-5 zinc alloy long-life fastener is also available.
Ken Webb has been involved in the metal construction industry for the past 27 years with Dynamic Fastener, Kansas City, Mo. To learn more, go to www.dynamicfastener.com.
