Nord-Lock Washers.

What are Nord-Lock Washers?

Nord-Lock washers, also known as Nord-Lock wedge washers or wedge locking washers, are precision locking washers engineered to secure bolted joints that are exposed to severe vibration and dynamic loads. Each Nord-Lock washer is supplied as a pre-assembled, glued pair, with inclined cams on the inner faces and radial serrations on the outer faces, with a cam angle greater than the rise angle of the thread. That wedge-locking geometry means the cams engage on installation, holding the assembly at high preload and securing the bolt against the rotational movement that leads to self-loosening.

Nord-Lock wedge washers are renowned for surviving the Junker test to DIN 65151, widely regarded as the most rigorous method of testing a bolted joint. That proven performance is why they’re specified across aerospace, energy, transportation, mining and heavy machinery, in the joints where a standard flat or spring washer fails to prevent self-loosening.

How Nord-Lock Washers Work

Understanding how Nord-Lock washers work comes down to one geometric principle: locking a bolted assembly with tension instead of friction. The pair is fitted cam to cam beneath the bolt head or nut and tightened with standard tooling. A socket and a torque wrench are the only tools you need. As the fastener is torqued, the radial serrations bite into both the underside of the bolt head and the mating surface. The two cams are left as the only part of the stack that can still turn against anything. If dynamic movement then tries to rotate the fastener, the cams are forced to slide and climb against one another, expanding the overall thickness of the pair and increasing clamping force to lock the joint firmly in place.

That behaviour matters most on assemblies that are cycled hard and are expensive to reach. On high-speed railway bogies, heavy mining plant, offshore transport infrastructure and wind turbine yaw and pitch connections, continuous operational vibration will steadily back standard hardware out of a joint. Routine re-torquing is both awkward and costly. Building Nord-Lock wedge washers into these assemblies holds preload where the designer intended it across the whole maintenance interval, eliminating unplanned downtime, protecting sensitive machinery and safeguarding vital infrastructure against catastrophic mechanical failure.

Materials Nord-Lock Washers Are Made From

Selecting the correct Nord-Lock washer material ensures optimal performance, structural integrity and longevity across varied environmental conditions, so Accu's range is manufactured from high-performance engineering metals chosen for their mechanical strength and corrosion resistance:

• Steel: High-grade steel providing exceptional mechanical strength and reliability for standard industrial applications.
• Steel - (EN1.7182): Specialised alloy steel engineered to maintain high clamping force and structural performance under heavy load conditions, hardened to 520 HV0.05.
• Stainless Steel - (316L): A premium grade used for our Nord-Lock stainless steel washers, delivering superior resistance to chloride pitting and atmospheric corrosion.
• Stainless Steel - (254): High-alloy austenitic stainless steel designed for aggressive environments such as marine and chemical processing applications.
• Nickel Alloy - Hastelloy (C-276): An advanced nickel-molybdenum-chromium alloy offering outstanding resistance to harsh chemicals and extreme environmental exposure.
• Nickel Alloy - Inconel (718): A high-strength nickel-chromium material built to maintain mechanical integrity and oxidation resistance under intense thermal stress.

To withstand more demanding operating environments, additional processing and protective finishes are available across the range:

• Surface Hardened: Raises surface hardness so the radial serrations bite into the mating surfaces and hold, and so the cam faces resist wear through repeated tightening.
• Through Hardened: Hardens the full section for joints carrying heavy or repeated loading.
• Delta Protekt®: A Nord-Lock Delta Protekt zinc flake coating that adds enhanced corrosion protection without the coating relaxing under load, an excellent choice for harsh environments.
• Delta Protekt® / Delta Seal: A combined coating system giving the highest level of resistance to environmental degradation across the range and a matte black aesthetic to components.

Sizes & Types of Nord-Lock Washers Available

Accu supplies a broad spectrum of Nord-Lock washer sizes to match precise engineering specifications across both metric and imperial thread standards:

• For Use With Thread Size (Metric): M3 (3 mm) to M130 (130 mm).
• For Use With Thread Size (Imperial): 1/4 inch to 1 inch.
• External Diameter (OD): 7 mm to 178 mm.
• Internal Diameter (ID): 3.4 mm to 133.4 mm.
• Pair Thickness (T): 1.6 mm to 9.5 mm.
• Continuous Use Temperature: -160 ºC to 700 ºC, depending on the base material selected.

Most thread sizes are offered in two types, a standard washer for general bolted joints and a large outside diameter version that spreads the clamping load over a wider area, which is the option to reach for on softer materials, oversized clearance holes and slotted fixings. Nord-Lock washer dimensions are held to tight tolerances throughout, and imperial variants are stocked alongside the metric range for thread sizes from 1/4 inch to 1 inch.

For less demanding, non-safety-critical scenarios, consider our range of internal and external locking washers, which still provide anti-vibration resistance at a fraction of the cost, or our Schnorr anti-vibration safety washers, where a conical spring action suits the joint better.

FAQs

Q: What is the purpose of a Nord-Lock washer?

A: The primary purpose of a Nord-Lock washer is to lock bolted joints using tension rather than friction. This prevents bolts and nuts from working loose when subjected to severe vibration, dynamic loads or high operational shock and it keeps working as the joint settles, which is where friction-based devices start to fail.

Q: How do Nord-Lock washers work?

A: Nord-Lock washers work in pairs. The radial serrations on the outer faces grip the bolt head and the mating surface, while the cams on the inner faces interlock. Because the cam angle is greater than the thread pitch, the fastener cannot rotate without lifting the cams and expanding the pair, which increases tension in the bolt rather than allowing it to back out.

Q: Are Nord-Lock washers reusable?

A: Yes, Nord-Lock washers are reusable. So long as the radial teeth and internal cams remain intact, clean and free from excessive wear, the pair can be reinstalled multiple times without losing locking performance. Inspect them for wear and damage before reuse, and re-lubricate the threads and contact surfaces prior to reassembly. There is no fixed number of reuses, the condition of the teeth and cams is what decides it.

Q: Are Nord-Lock washers any good?

A: Nord-Lock washers are highly regarded for their ability to maintain high preload and prevent loosening in bolted joints under severe vibration and dynamic loads. The wedge-locking mechanism keeps the assembly secure where conventional locking washers gradually give up their grip, which is why they are a standard choice for safety-critical applications across industry.

Q: Nord-Lock washer vs spring washer, which is better for vibration?

A: Nord-Lock washers offer significantly greater reliability than traditional spring washers in high-vibration applications. A split washer or spring washer relies purely on friction and elastic tension, both of which fall away quickly under dynamic stress. A Nord-Lock washer uses a mechanical wedge lock that actively increases tension if the fastener attempts to rotate loose. For joints with minimal vibration where cost is the deciding factor, a spring washer may still be the sensible choice.

Q: When should you not use a Nord-Lock washer?

A: Nord-Lock washers should not be used where the contact surfaces are uneven, as irregularities stop the locking mechanism seating properly. They are also unsuitable for soft metals and plastics, where the serrations embed into the material instead of gripping it, and they should not be paired with free-spinning non-rotation washers or countersunk fasteners.

Q: Can Nord-Lock washers be used with any bolt?

A: Nord-Lock washers can be used with almost all standard high-tensile bolts and nuts, including grades 8.8, 10.9 and 12.9, and are matched to the fastener by thread size rather than by head type. For the washer to work, the mating surface must be softer than the washer so the external radial serrations can bite into it, and the additional pair thickness needs to be allowed for in the grip length of the joint.

Bespoke Nord-Lock Washers Manufacture.

High precision, bespoke manufacture of Nord-Lock Washers to customer specification. State of the art facilities specialising in both small batch prototyping and large scale manufacture.