6 Best Spring Lock Washers for Maintaining Tension

Fasteners are the silent backbone of every structure, holding the integrity of a roof together through thermal expansion, high winds, and structural settling. Without proper tension, vibration eventually works a bolt loose, leading to rattling metal panels or sagging trusses. Selecting the right spring lock washer transforms a potential failure point into a secure, long-term connection. Understanding these small components is the difference between a roof that performs for decades and one that requires constant maintenance.

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Hillman Group Helical Split Washer: Best Overall

The helical split washer is the industry standard for general-purpose construction. Its simple, coil-spring design provides a consistent reactive force that keeps nut tension against the mating surface.

When securing rafters or mounting roof-top HVAC units, this washer offers the perfect middle ground between performance and cost. It is easy to source in bulk, making it the default choice for most framing projects.

Avoid over-tightening with these washers, as flattening them entirely can diminish their ability to provide spring tension. Use these where standard mechanical vibration is expected, but avoid them for high-torque critical joints where precision is paramount.

Nord-Lock Wedge-Locking Washers: For High Vibration

When equipment vibrates constantly—like industrial exhaust fans or motorized venting systems—standard split washers fail. Nord-Lock washers utilize a cam-wedge effect that physically prevents the bolt from rotating.

These are essential when working on commercial metal roofing systems where heavy equipment creates ongoing seismic or kinetic force. By increasing the tension during any loosening attempt, they physically lock the assembly in place.

While the price point is significantly higher, the investment is justified for critical hardware that is difficult or dangerous to access for maintenance. Always install them as a pair to ensure the cam faces mate correctly.

Belleville Disc Springs: For High-Load Applications

Belleville washers are conically shaped, providing significantly higher load-bearing capacity than standard split rings. Their geometry allows them to act as a spring, compensating for thermal expansion in metal-on-metal connections.

Use these when fastening heavy-gauge steel or in assemblies where temperature fluctuations are extreme. The conical shape maintains pressure even as bolts expand and contract under the intense heat of a summer day on a dark, reflective roof.

These washers require specific torque calculations to be effective. Ensure the bolt grade matches the intended load, or the spring force will not be properly utilized.

Shakeproof Internal Tooth Lock Washer: Best Grip

The internal tooth design features small, serrated edges that bite into the underside of the bolt head. This creates a friction-based lock that is superior for light-duty applications or soft-metal substrates.

These are the go-to for grounding electrical components on metal roofs or securing thin gauge trim pieces. The teeth create an excellent contact point, which can even improve electrical conductivity in shielded systems.

Do not use these on hardened steel surfaces or where high vibration will eventually cause the teeth to lose their grip. They are meant for static, lower-tension applications where preventing rotation is the primary goal.

CURT Manufacturing Split Washers: For Automotive Use

Originally engineered for trailers and hitches, these split washers are built to withstand extreme road shock and oscillating loads. They are highly durable and resist deformation under heavy duty cycles.

For roof-mounted solar rack systems that need to withstand high wind uplift, these provide a robust solution. They maintain tension effectively even when the structure is subjected to the repetitive “oil-canning” or vibration of metal sheets in high wind.

Because they are often zinc-plated, they are best suited for environments where they remain dry or under protective flashing. If exposed to salt-spray or high humidity, look for a stainless equivalent.

Grainger Zinc-Plated Split Washer: Bulk Value Pick

When the job requires hundreds of fasteners for basic assembly, professional contractors lean toward bulk-packaged, zinc-plated split washers. They provide reliable, budget-friendly performance for non-critical, static framing tasks.

These washers are ideal for indoor construction or sheltered attic spaces where corrosion is not the primary enemy. They serve their purpose in blocking nut migration effectively enough for standard residential structural connections.

Always buy more than the estimate calls for, as the plating can occasionally be inconsistent in bulk batches. Inspect for surface burrs before installation to ensure a flat, even seat.

How Spring Lock Washers Actually Maintain Tension

The logic behind a spring washer is simple physics: the washer acts as a compressed spring. By creating a gap, the washer forces the nut and bolt to fight against each other.

This creates a high-friction environment that resists the rotational torque caused by vibration. When properly tightened, the washer undergoes elastic deformation, constantly pushing back against the bolt head.

If the washer is tightened until it becomes completely flat, the spring effect is lost and it essentially becomes a standard flat washer. Effective tension maintenance requires the washer to remain in its active, pre-loaded range.

Split Ring vs. Tooth Lock vs. Wedge: Which to Use

Choosing the right type depends entirely on the material and the motion expected at the joint. * Split Ring: Best for general, everyday mechanical fastening and standard vibration. * Tooth Lock: Best for preventing rotation in thin-gauge metal or electrical bonding. * Wedge-Locking: The only choice for high-vibration, critical load-bearing assemblies.

For general framing, keep split rings on hand for 90% of tasks. Reserve specialized wedge-lock washers for structural steel or vibrating machinery mounts.

When You Should NEVER Use a Split Lock Washer

There are specific instances where spring lock washers can do more harm than good. Avoid them on soft materials like aluminum, where the hardened teeth or split edges can dig in and cause structural degradation.

Do not use them on assemblies where extreme high-torque is required for structural clamping. In these cases, a plain, hardened flat washer is superior, as it allows for an accurate torque reading without the “false” friction of a spring.

Finally, do not rely on them to fix a bolt that is already stripped or a hole that is over-drilled. A lock washer is designed to maintain tension in a healthy assembly, not to compensate for faulty workmanship.

Choosing the Right Material: Stainless vs. Zinc

Material selection is dictated by the environment of the roof or building. * Zinc-Plated: Cost-effective and suitable for dry, interior, or well-flashed areas. * Stainless Steel (304/316): Mandatory for exterior exposure, coastal regions, or high-moisture environments.

In a coastal zone, zinc will corrode rapidly, leading to rust streaks on roofing panels and eventual failure of the fastener itself. Always match the washer material to the bolt grade; mixing incompatible metals, such as stainless steel bolts with carbon steel washers, can lead to galvanic corrosion.

Getting the fastener assembly right the first time prevents costly callbacks and ensures the structural longevity of the project. Whether installing heavy HVAC equipment or simple trim, a properly specced spring lock washer is the cheapest insurance against future mechanical failure.