Square Nuts

Four Sided Nuts

Square nuts can be used in a channel or welded to other steel products. A square nut is a four-sided finish nut. Compared to standard hex nuts, square nuts have greater surface contact with the part being fastened. Therefore, they have a greater resistance to loosening than standard hex nuts, but also greater resistance to tightening, making these nuts a little harder to install securely. They are also much less likely to become rounded-off after repeated loosening/tightening cycles.

Square nuts are typically mated with square-headed bolts. Square nuts are used along with flat washers to avoid damage from its sharp edges and increase the strength of the fastener. They are installed on the opposite side of the materials being fastened. With the bolt head or machine screw head on the other side, they compress the materials together for a secure fit.

Stainless Steel

18-8 or 304 grades of Stainless steel are suitable for many general purpose applications, especially freshwater and non-salt water wet environments. Corrosion-resistant and durable, 18-8 stainless steel is equivalent to the A2 grade of stainless steel.

For much more corrosive environments, such as in saltwater or marine applications, 316 stainless steel is the ideal choice. 316 Stainless steel is equivalent to A4 stainless steel.

Zinc Plated Steel

Zinc is by far the most common and economical type of plating for fasteners. The zinc plating adds a protective "sacrificial" top layer against corrosion while also adding a shiny finish to the threaded rod. Zinc plating is ideal for indoor use, where it won't be constantly exposed to harsh elements.

Hot Dip Galvanized Steel

Hot-dip galvanizing is done by submerging the fastener in molten zinc to provide a corrosion protecting finish. Essentially, the added zinc that's applied through the galvanization process serves as a "sacrificial" layer of protection to keep the steel underneath from degrading or being damaged.

You'll find hot-dip galvanized fasteners frequently used in situations where corrosion resistance is needed without the cost of stainless steel. It is considered superior to stainless steel in terms of cost and life-cycle. For applications where the fastener will constantly be exposed to corrosive materials, you'll want to use stainless steel instead.

Note: hot-dip galvanized fasteners tend to be a little larger, with thicker threading, because of the added layer of zinc. To compensate, hot-dip galvanized nuts are tapped larger to be thread effectively on hot-dip galvanized bolts. You will have difficulty trying to fasten non-hot-dip galvanized nuts to hot-dip galvanized bolts, screws, or all thread.

Square Nut Specifications - 304 Stainless Steel

Size Across Flats
(Max-Min) 		Thickness
(Max-Min) 		Square Shape
#4 0.250-0.241 0.098-0.087 Flat
#6 0.312-0.302 0.114-0.102 Flat & Beveled
#8 0.344-0.310 0.130-0.117 Beveled
#10 0.375-0.362 0.130-0.117 Beveled
1/4" 0.438-0.423 0.193-0.178 Flat & Beveled
5/16" 0.562-0.545 0.225-0.208 Beveled
3/8" 0.625-0.607 0.257-0.239 Beveled
1/2" 0.812-0.788 0.458-0.418 Beveled
5/8" 1.000-0.969 0.569-0.525 Beveled
3/4" 1.125-1.088 0.680-0.632 Beveled

Square Nut Specifications - 316 Stainless Steel

Size Across Flats
(Max-Min) 		Thickness
(Max-Min) 		Square Shape
1/4" 0.438-0.423 0.193-0.178 Flat & Beveled
5/16" 0.562-0.545 0.225-0.208 Beveled
3/8" 0.625-0.607 0.257-0.239 Beveled
1/2" 0.812-0.788 0.458-0.418 Beveled
5/8" 1.000-0.969 0.569-0.525 Beveled
3/4" 1.125-1.088 0.680-0.632 Beveled

Square Nut Specifications - Zinc Plated Steel

Nut Size Width Across Flats Thickness
1/4" Max 0.438-Min 0.423 Max 0.235-Min 0.203
5/16" Max 0.562-Min 0.545 Max 0.283-Min 0.249
3/8" Max 0.625-Min 0.607 Max 0.346-Min 0.310
7/16" Max 0.750-Min 0.728 Max 0.394-Min 0.356
1/2" Max 0.812-Min 0.788 Max 0.458-Min 0.418
5/8" Max 1.000-Min 0.969 Max 0.569-Min 0.525
3/4" Max 1.125-Min 1.088 Max 0.680-Min 0.632
7/8" Max 1.312-Min 1.269 Max 0.792-Min 0.740
1" Max 1.500-Min 1.450 Max 0.903-Min 0.847

Square Nut Specifications - Hot Dip Galvanized Steel

Nut Size Width Across Flats Thickness
1/4"-20 Max 0.438-Min 0.423 Max 0.235-Min 0.203
5/16"-18 Max 0.562-Min 0.545 Max 0.283-Min 0.249
3/8"-16 Max 0.625-Min 0.607 Max 0.346- Min 0.310
7/16"-14 Max 0.750-Min 0.728 Max 0.394- Min 0.356
1/2"-13 Max 0.812-Min 0.788 Max 0.458-Min 0.418
5/8"-11 Max 1.000-Min 0.969 Max 0.569-Min 0.525
3/4"-10 Max 1.125-Min 1.088 Max 0.680-Min 0.632
7/8"-9 Max 1.312-Min 1.269 Max 0.792-Min 0.740
1"-8 Max 1.500-Min 1.450 Max 0.903-Min 0.847
1-1/8"-7 Max 1.688-Min 1.631 Max 1.030-Min 0.970
1-1/2"-6 Max 2.250- Min 2.175 Max 1.348-Min 1.276

FAQs

Why are nuts hexagonal in shape?

Must nuts have a hexagonal shape because it's easier to grip. With six sides, you can turn a nut just one-sixth of the way to reach the next flat parallel. In contrast, you have to turn one-quarter of the way for square nuts.

How do you tighten a square nut?

Square nuts can be tightened with pliers or a wrench, making them ideal for use in blind locations. The pliers or wrench only need a sturdy grip to secure these nuts.

Why are square nuts not used as much as hex nuts?

Square nuts were common mostly because they were easy to manufacture, especially by hand. Hex nuts are more common now, thanks to the six sides granting more angles that a tool can fasten from, making it generally easier to fasten down.

What is stainless steel good for?

Stainless steel is good for general purpose applications, especially those involving water or freshwater. Suppose you need stainless steel for more corrosive environments, such as marine or salt-water applications. In that case, we recommend the 316 grade of stainless steel.

What is zinc plated steel?

Zinc plated steel is steel that goes through adding a layer or coating of zinc to protect the steel from corrosion. The added layer of zinc sacrifices itself to keep the steel from rusting, even if the plating is damaged.

What is hot-dip galvanized steel?

Hot-dip galvanized steel is steel submerged in a molten zinc bath to give the steel a protective corrosion resistant coating.