Square Washers Basics

Square washers are beneficial to use instead of standard round washers when levelling, or alignment is needed for an application. Like round washers, square washers are often used to distribute a larger load, but they also perform as shims and add the advantage of providing edge-to-edge contact to resist turning, as well as providing a larger bearing surface as compared to a round washer.

Bevel washers are square or rectangular washers with a beveled 1 to 6 ratio surface, to compensate for a lack of parallelism in structural components. The beveled surface allows for a snug fit between both the flat and the sloped material that is being bolted together, which creates a solid and tight fit overall.

Types of Square Washers

Square Plate Washers

Square Washers called construction square plate washers can be used instead of round washer for applications such as timber building and concrete floors; they are used with all fasteners for larger load distribution and bolting through a wall or timber. While disc washers operate solely as load distributors, square flat washers serve a second role. Their thick metal forms have that standard bolt opening in the center, plus a wide surface area, a feature that spreads torque and head load, but they also perform as shims. That means the bolt crown can be lifted away from the anchored part. It also means that a multi surface project won't deform or bend when the fastener is tightened.

Malleable Iron Bevel Washers

Bevel washers are square or rectangular washers with a beveled 1 to 6 ratio surface. Malleable iron bevel washers are used with American standard beams and channels in structural applications, to compensate for lack of parallelism. For bevel washers to be used with A325 and A490 structural bolts, please see F436 bevel washers.

ASTM F436 Bevel Washers

F436 thru hardened bevel washers are square or rectangular washers with a beveled 1 to 6 ratio surface. F436 Bevel Washers are larger than Malleable Bevel Washers. For use with American standard beams and channels to compensate for lack of parallelism. F436 bevel washers are designed for structural applications and are commonly used with ASTM F3125 Grade A325 and Grade A490 fasteners.

Common Finishes of Square Washers

Square washers are commonly available in plain and galvanized finishes.

Black or Plain Finish Square Washers

Flat washers are unfinished or will have a minimally protective finish. Black flat washers offer near zero corrosion resistance, though black oxide coatings or oiled coatings do offer increased corrosion resistance over unfinished flat washers.

• Black flat washers are commonly referred to as plain finish, black, black oxide, black phosphate, bare or light oil coated.

Galvanized Flat Washers

Galvanized flat washers are coated with a sacrificial zinc coating that acts as an anode to prevent the fastener underneath from corroding.

• Hot Dipped Galvanized: Fasteners are dipped in a bath of molten zinc.