ASME B18.6.3 Plain 18-8 Stainless Steel Machine Screw Hex Nut, #4-40 Thread Size, 3/32" Width Across Flats, 1/4" Thick (Pack of 100)
Most often used on machine screws and threaded rod, these general purpose nuts are for low-strength assemblies.  Hex Nuts have flat tops with chamfered corners; bottoms may be flat or chamfered.  Hex drive systems are driven with a wrench.Stainless steels are used for their corrosion resistance, high-temperature strength, scaling resistance, and low-temperature toughness.  These properties account for their extremely wide use in practically every industry.  Austenitic Stainless Steels are alloys of iron and carbon that contain between 16% and 30% Chromium, a maximum of 0.15% carbon, along with Nickel (or Manganese), and other alloying elements.  The chromium, which helps develop a passive surface oxide film, provides corrosion resistance in stainless steels.   Austenitic Stainless Steels are designated by a 3 digit SAE Stainless Steel Grade beginning with the number 3 (e.g. 304, 316).  Another common naming convention for Austenitic Stainless Steels are 18/8, 18/10, 18/0, etc. where the 18 refers to the % of Chromium and 8 to the % of Nickel contained in the material.    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.