Safety & Conical Spring Washers
These are used for locking a device and reducing the vibration. They reduce loosening by preventing unscrewing rotation of the fastening device; locking washers are usually also spring washers.
Washers are available in a wide range such as spring washers, star washers, multi-tooth washers, disc spring washers, wave washers, taper washers, safety washers etc.
Serrated Safety Washers Type S – Schnorr Type 
Advantages
– The cross section ensures locking effect at the outside diameter.
– Due to the closed ring form, high degree of pretensioning is achieved.
– Sliding surfaces allow tightening with damaging the mating surfaces.
– High resistance to vibration due to positive locking of the serrations
– Suitable for a wide range of screw/bolt heads minimizing stocks.
Afnor Contact Lock Washers – NF E-25 511 
Contact Washers are Conical shaped Lock Washers formed with a ribbed top surface. The conical shape exerts locking force 360 degree around the underside of the screw head/ nut by generating tension. The ribbed top surface further enhances the locking force and resists the torqued fastener connection potential for loosening under pressure and vibration. This is a single-sided toothed and non-slip locking washer, providing the designer the ability to secure wobble-prone screw effectively. It is particularly suitable for use on slot fasteners, dynamic cross-loaded to the screw connections and applications that require high biasing forces.
These washers are widely used in locomotives, appliances, elevators, electrical towers, medical machinery and electronic equipment.
Range available: Sizes – M3 to M20
Materials SS-304 / SS-316. As per NFE – 25511