Alloy Steel Set Screw, Black Oxide Finish, Hex Socket Drive, Meets ASME B18.3/ASTM F912, 3/16" Length, #4-40 UNC Threads, Imported (Pack of 100)
Set Screws are often used for holding a pulley, gear, or other parts from turning relative to a shaft.Alloy Steel is steel that has been alloyed with other materials to improve overall physical properties.  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).  Tensile strength ranges for the alloys typically used in these fasteners range from 170,000 to 180,000 psi (pounds per square inch), making these amongst the strongest of materials.Hex socket drive systems are driven by hex wrenches or power tools with hexagonal bits.A threaded fastener's size name includes information about the major external diameter, followed by the threads per inch, which indicates if it is coarse or fine.  Coarse threads are better when working with brittle materials; they are sturdier and are easier to thread and unthread compared to fine.  Coarse threading also allows for thicker coatings and platings.