A square nut, or square head nut, is a four-sided nut that is designed for use with a square head bolt and flat washer. Square nuts offer greater surface contact with the part being fastened compared to a standard hex nut, and therefore provide greater resistance to loosening. They also work well in tight spaces when using pliers or a wrench, and are less likely to become rounded-off after repeated loosening/tightening cycles. The square head design however leaves sharp corners that can sometimes be destructive to wood or metal surrounding the nut. Flat washers provide not only protection from damage, but they also succeed in spreading the load of the forces pressing against the nut across a larger area, giving the fastener more strength. Over the years, hex nuts have replaced square nuts for most applications, however they can still be found in furniture manufacturing, restoring vintage automobiles, railroad track construction, or used as a blind nut.
Square Nut Options
As a square nut supplier, AFT offers a wide variety of sizes including diameters ranging from #6 up to 1-1/2”, and all nuts are available in both convenient small package and cost-effective bulk containers. Choose from steel square head nuts in plain, zinc, or hot dipped galvanized finishes. Or, AFT’s in-house plating shop is always available if your application requires Xylan, E-Nickel, Tin, Cadmium, Zinc Phosphate, Silver or a variety of other custom coatings. Square nuts can have standard, fine or coarse threading and most meet ASTM A194, ASTM A563, or ASTM F594 standards.