DIN25201 Double Fold Self-locking Washer Pairs

Pairs use a two-piece wedge-locking structure to resist loosening in bolted joints exposed to vibration and dynamic movement. The two washers are supplied together with their inclined inner surfaces facing each other, while the radial teeth on the outer surfaces engage with the bolt head or nut and the joint surface. This creates a different locking mechanism from conventional washers that rely mainly on friction.

When vibration causes relative movement in the joint and creates a tendency for the fastener to rotate, the two washer halves can move against each other along their inclined inner surfaces. The wedge geometry converts this movement into an increase in tension within the joint, resisting further loosening. When the joint returns from the displaced position, the washer pair helps maintain the original clamping condition. The locking effect is therefore generated by the wedge surfaces and surface engagement, rather than by adhesive or friction alone. The washers are supplied as a pre-assembled pair, making it easier to maintain the correct orientation during installation. They are best suited to relatively flat and smooth metallic contact surfaces where the outer teeth can engage effectively. For non-metallic joint materials, a suitable metal plate can be introduced at the fastening location to provide an appropriate contact surface for the locking washer.

Specification:

DIN 25201 self-locking washer pairs consist of two matching washers with opposing wedge surfaces on the inside and radial teeth on the outside. The two components are supplied as a pre-assembled pair and installed with the wedge surfaces facing each other. The outer teeth are intended to engage with relatively flat and smooth contact surfaces, while the inclined inner surfaces provide the wedge-locking action between the two washers. Key specifications include nominal bolt size, inside diameter, outside diameter, combined washer thickness, material, hardness, and surface finish. Carbon steel and stainless steel options can be selected according to the mechanical and environmental requirements of the joint. During installation, the washer pair does not depend on a special locking adhesive, and conventional hand tools or powered installation equipment can be used according to the requirements of the assembly.

Dimension Chart of DIN25201 Double Fold Self-locking Washers:

The DIN 25201 dimension chart provides the key measurements for selecting the correct self-locking washer pair according to the mating bolt size. Since each product consists of two matching washers supplied as a pre-assembled pair, the dimensions should be considered for the complete washer configuration as well as for the individual washer geometry. Key dimensions include the nominal bolt size, inner diameter (d1), outer diameter (d2), and washer thickness (s). The inner diameter determines compatibility with the bolt shank, while the outer diameter defines the contact area beneath the bolt head or nut. The washer thickness is also relevant when checking the available space and the overall stack height of the bolted joint.