Steel Self-Drilling Screw, Zinc Plated Finish, Hex Washer Head, External Hex Drive, Sealing, Includes Washer, 1-1/4" Length, #8-18 Threads (Pack of 100)

Unlike tapping screws, these screws drill a hole and tap a thread in a single operation. All you need to install them is a power driver. For effective fastening, the drilling point must fully penetrate all pieces of material being fastened before the first thread engages. The washer and hex head are formed together as one piece. The underside of the head provides a large flat bearing surface that reduces the likelihood of crushing mating surfaces. When you drive this screw, a flexible black EPDM rubber washer bonded to a metal washer compresses, forming a tight seal. Ideal for metal structures and assemblies. Head height includes compressible washer. Length is measured from under washer. Fully threaded. Steels are designated by a 4 number SAE Steel grade.  The first two digits indicate the primary materials used to form the steel.  The last 2 digits identify the percentage of carbon for the alloy (in hundredths).  The steel used in these fasteners has a tensile strength ranging from 100,000 to 150,000 psi (pounds per square inch).  Zinc Plating helps to prevent corrosion.Hex head fasteners can be driven with simple wrenches, and require minimal clearance above the fastener because they can be driven or loosened from the side.

• Create their own threads when driven into material
• Zinc Plated Steel fasteners are suitable where strength and corrosion resistance are primary considerations
• Hex head for easy driving
• Length is measured from under the head