Compare arandelas planas y de resorte: cuándo usar cada tipo, distribución de carga vs antiaflojamiento y criterios de selección.
Functions of Flat Washers vs Spring Washers
Flat washers and spring washers serve fundamentally different purposes in bolted assemblies, yet they are frequently confused or misapplied. Flat washers (DIN 125 / ISO 7089) distribute the clamping load over a larger surface area, protecting the base material from damage and preventing the bolt head or nut from digging into soft materials. They also provide a smooth bearing surface that helps achieve consistent clamp force. Spring washers (DIN 127 / ISO 7090), also called split lock washers, serve as an anti-loosening device. The split creates a spring action that maintains tension on the bolt even if some preload is lost. However, spring washers provide only moderate vibration resistance and are increasingly being replaced by more effective locking methods in critical applications. For construction projects in Africa, the common practice is to use a flat washer under both the bolt head and nut, with a spring washer added on the nut side when vibration is a concern. This combination provides both load distribution and some degree of anti-loosening protection.
| Property | Flat Washer | Spring Washer |
|---|---|---|
| Primary Function | Load distribution | Anti-loosening |
| Standard | DIN 125 / ISO 7089 | DIN 127 / ISO 7090 |
| Material | Steel, stainless, nylon | Spring steel, stainless |
| Surface Protection | Yes — prevents gouging | No |
| Vibration Resistance | None | Moderate |
| Reusability | Yes | Limited (fatigue) |
Flat Washer Types and Specifications
Flat washers come in several configurations suited to different applications. Standard flat washers (DIN 125 Form A) have a normal outside diameter and are used for general purposes. Form B washers have a larger outside diameter for soft materials or oversize holes. Hardened flat washers (DIN 6917) are used with structural bolts (Grade 8.8 and above) and have higher hardness ratings to prevent deformation under high clamping forces. Heavy-duty flat washers (DIN 433) have a smaller outside diameter and are used in confined spaces. Material choices include mild steel (standard), stainless steel (A2/A4 for corrosion resistance), brass (electrical applications), and nylon (non-conductive, lightweight). For construction in coastal African regions, stainless steel flat washers paired with stainless steel bolts and nuts provide the most durable assembly. When ordering flat washers in bulk, specify the standard, material, inside diameter, outside diameter, thickness, and surface finish.
| Bolt Size | ID (mm) | OD (mm) Form A | Thickness (mm) | Hardness (HV) |
|---|---|---|---|---|
| M6 | 6.4 | 12 | 1.6 | 140-200 |
| M8 | 8.4 | 16 | 1.6 | 140-200 |
| M10 | 10.5 | 20 | 2.0 | 140-200 |
| M12 | 13.0 | 24 | 2.5 | 140-200 |
| M16 | 17.0 | 30 | 3.0 | 140-200 |
Spring Washer Effectiveness and Alternatives
The effectiveness of spring washers as anti-loosening devices is a subject of ongoing debate in the engineering community. Research has shown that standard split helical spring washers provide limited vibration resistance under dynamic loading conditions. The spring force generated by a compressed split washer is typically only 5-10% of the bolt preload, which may be insufficient to prevent loosening in high-vibration environments. For applications requiring reliable anti-loosening, several alternatives outperform spring washers. Nord-Lock wedge lock washers use a cam mechanism that increases tension under vibration. Prevailing torque nuts (nylon insert or deformed thread) provide consistent locking force. Thread-locking adhesives (Loctite) create a chemical bond. For structural construction in seismic zones like parts of East Africa, double nut arrangements or castle nuts with cotter pins are specified. When spring washers are used, they should be installed between the nut and the flat washer, never directly against the base material. Replace spring washers after each disassembly as they lose elasticity with repeated compression cycles.
Should I always use a spring washer with a nut?
No. For static loads with no vibration, a flat washer alone is sufficient. Spring washers are only needed when vibration or dynamic loading is expected. Overuse of spring washers adds cost without benefit.
Can I stack multiple spring washers for more locking force?
Stacking spring washers is not recommended. It does not proportionally increase locking force and can create uneven bearing surfaces. Instead, use a more effective locking method such as a Nord-Lock washer or prevailing torque nut.
Need washers for your fastener assemblies? Get bulk pricing from TradeGo Fasteners.
Get Quote