SN 70093 Contact Washer

SN 70093 is a conical contact washer used to establish reliable electrical contact in bolted grounding and bonding connections. Its defining feature is a spring-loaded conical form with six contact teeth on the underside. When the teeth are positioned against the contact surface, they can penetrate a protective coating and reach the underlying metal, helping maintain electrical continuity through the bolted joint. Siemens installation documentation specifies SN 70093 contact washers for earthing connections on coated steel components.

The product is also commonly identified as a contact disc or toothed contact washer. Keller & Kalmbach lists SN 70093 as a “Contact disc” and identifies it as toothed for electrically conductive connections, with six teeth intended to face the contact surface. The same product data associates SN 70093 with NFE 25-511 K.

SN 70093 and NF E 25-511 should not be treated as two interchangeable names for exactly the same specification. SN 70093 is a Siemens specification designation, while NF E 25-511 K identifies the toothed form within the corresponding contact washer standard family. Technical catalogues place SN 70093 in the toothed category of conical contact washers, while other NF E 25-511 forms cover different contact washer geometries and applications.

Unlike a conventional plain washer, SN 70093 is intended to provide an electrical contacting function in addition to its spring-loaded fastening effect. It is particularly relevant where painted, coated, or otherwise finished metal surfaces would otherwise interrupt direct metal-to-metal electrical contact. Correct orientation is important: the toothed side should face the surface requiring electrical contact.