NFE 25-511 Serrated Conical Contact Washers

NFE 25-511 serrated conical contact washers are French-standard locking washers with a conical spring profile and serrated contact surfaces. They are commonly identified as AFNOR contact washers, serrated conical spring washers, or simply contact washers. Unlike a conventional flat washer, the conical form provides elastic deflection while the serrated surface creates mechanical engagement with the mating surface. This combination makes the washer suitable for bolted joints where resistance to loosening and retention of clamping force are important.

The NFE 25-511 range includes different dimensional forms for different fastener and installation conditions. Type M is a common general-purpose form used with hexagon head screws, bolts, and nuts. Type S is associated with smaller outer dimensions and cylindrical or similar screw-head applications, while Type L provides a larger bearing area and is used where a wider contact surface is required, including applications involving larger holes or softer supporting materials. Industry product ranges also identify Type K contact washers for electrical connections, where the teeth are intended to penetrate painted or coated surfaces and establish electrical contact. The exact type and dimensions should therefore be selected according to the mating fastener and joint geometry.

The distinguishing feature of NFE 25-511 is the combination of conical spring action and serrated contact teeth. The spring profile maintains an elastic load within the joint, while the serrations engage the mating surfaces when the fastener is tightened. This makes the product different from conventional flat washers, which primarily distribute bearing pressure, and from standard toothed lock washers, which do not have the same conical spring geometry.

NFE 25-511 contact washers are used in mechanical equipment, industrial assemblies, electrical equipment, transportation equipment, and other bolted connections exposed to vibration or requiring reliable surface contact. Stainless steel A2 and A4 versions are available in the market, while carbon spring steel versions are also commonly supplied in raw or zinc-plated finishes.