Do Square Metal Washers Prevent Loosening?

Square metal washers are widely used in structural connections, heavy-duty frames, and timber construction where enhanced load distribution and fastening stability are required. While they are not classified as lock-washers, square washers do contribute indirectly to preventing loosening by providing a larger, flat bearing surface that stabilizes the joint.

Compared with standard round washers, square metal washers offer greater surface contact with both the bolt head/nut and the mounting material. This expanded contact area reduces local pressure, minimizes embedment, and keeps the fastener seated more uniformly. Their shape helps resist lateral movement, which provides additional stability under dynamic loads. Although they are not a substitute for dedicated locking components—such as spring washers, serrated washers, or chemical thread-locking solutions—they enhance overall joint reliability when used in the correct application.

Square metal washers do not lock the fastener, but they play an important role in preventing loosening caused by surface deformation, uneven load distribution, and bolt rotation, especially in structural installations.

Differences Between DIN 6916, DIN 435, and DIN 436

DIN 6916 – High-Strength Structural Washer

DIN 6916 washers are designed for high-strength steel bolting assemblies, particularly for structural steelwork. They have a thicker profile and higher hardness level compared with standard washers.

Key characteristics include:

High load-bearing ability suitable for pre-loaded bolts (e.g., HV or HSFG systems).

Hardened steel construction, providing resistance to compression and deformation.

Typically used in steel bridge connections, building frames, and industrial machinery requiring high tightening torque.

Their enhanced strength makes them the preferred option in joints where rotational loosening or slip must be minimized under dynamic or cyclic loads.

DIN 435 – Square Washer for Steel Channels (T-Beams)

DIN 435 square washers are widely used with channel beams (U- or I-sections) in structural and construction applications.

Their essential features include:

A square shape that aligns with channel slots, preventing rotation.

Larger outer dimensions that distribute load effectively across steel surfaces.

Designed mainly for structural bolts with tapered flanges.

They are common in building installations involving cable trays, support frames, machine foundations, and heavy wooden structures.

DIN 436 – Square Washer for Timber and Concrete Structures

DIN 436 washers are primarily intended for timber constructions and formwork.

They are characterized by:

A square profile with increased surface area, ideal for soft or uneven materials.

Prevention of bolt head embedment into wood or concrete.

Use in formwork panels, wooden beams, and foundation anchor bolts.

Compared with DIN 435, DIN 436 washers generally have slightly different thicknesses and dimensions tailored to construction materials that require broader load spreading.