Nord-Lock Nuts.

What are Nord-Lock Nuts?

Nord-Lock nuts, also known as wedge lock nuts, are a pivotal component in Accu's precision locking nuts range, pairing a nut with captivated Nord-Lock washers to prevent loosening under vibration and dynamic loads. Each Nord-Lock nut is supplied as a single assembly consisting of a hexagon nut with a bonded pair of wedge locking washers held captive beneath it. The washers carry inclined cams on their mating faces and radial serrations on the faces that meet the nut and the joint surface. Because the washers arrive captive and correctly oriented, the wedge lock engages the moment the nut is tightened, holding high preload and securing the fastening against vibrational loosening. They also help remove the fitting errors that come with loose washers on the shop floor.

The wedge-locking technology at the heart of a Nord-Lock nut is proven under the Junker test to DIN 65151, the industry's benchmark for transverse vibration. It was the first securing washer system to be CE marked for European steel construction. That combination of tested vibration performance and certification is why wedge lock nuts are specified on bridges and structural steelwork and on trucks, trailers and heavy plant where a fastening that backs out carries a real safety cost.

How Nord-Lock Nuts Work

Nord-Lock nuts lock a joint with tension rather than friction. They install with standard tooling and no thread locking fluid, insert or special surface preparation. As the nut is torqued to specification, the radial serrations on the outer washer face bite into the joint surface while the opposing face grips the underside of the nut, leaving the two cam faces in the middle as the only interface that can ever move. Because the cam angle is greater than the pitch of the mating thread, any attempt by vibration to rotate the nut has to lift the cams over one another, which expands the captive pair and increases tension in the bolt instead of releasing it. Supplying the nut and washers as one captive unit also means the assembly cannot be built the wrong way round, which matters on production lines and in the field where a reversed washer pair would leave the joint unsecured.

Two jobs show this off well. A bridge or steel structure takes cycling loads from traffic and wind all day, which can cause the bolts in the joint to relax and lose preload. If one fastening ceases to carry its share of the load, that pushes its share onto the ones beside it, increasing the likelihood that they’ll relax or fail. A truck or trailer wheel gets the same treatment, which is why wheel nuts use a fine thread and a protective coating. Using Nord-Lock nuts helps prevent loosening and means the joint reaches its next inspection as tight as when it left the workshop. 

Materials Nord-Lock Nuts Are Made From

Accu's range of Nord-Lock nuts is manufactured from a high-performance engineering steel, selected for the clamping force and structural integrity these joints demand:

• Steel - (EN1.7182): Specialised high-strength alloy steel engineered to maintain high clamping force and structural performance under heavy and repeated load conditions, hardened to 465 HV1.

Protective finishes and additional processing are applied across the range to suit the operating environment:

• Zinc - Nickel Plated: Delivers extreme corrosion resistance with enhanced wear protection, the standard finish on Nord-Lock combi nuts.
• Delta Protekt®: A zinc flake coating giving extreme corrosion resistance without relaxing under load, the standard finish on Nord-Lock wheel nuts.
• Through Hardened: Hardens the full section of the nut so it carries heavy and repeated loading without deforming at the bearing face.

Sizes & Types of Nord-Lock Nuts Available

Accu's range of Nord-Lock nuts is available in a variety of sizes and specific types to accommodate a range of demanding engineering needs:

• Thread Size: M6 (6 mm) to M24 (24 mm), plus 7/8-11 BSF in imperial.
• Socket Size (J): 10 mm to 36 mm.
• Nut Thickness (H): 8.7 mm to 33 mm.
• Outside Diameter (OD): 12.5 mm to 48 mm.
• Thread Specification: Metric Coarse and Metric Fine.
• Continuous Use Temperature: -50 ºC to 150 ºC.

The range splits into two types, each matched to a different job:

• Nord-Lock Combi Nuts: A metric coarse nut with a captive Nord-Lock washer pair in zinc nickel plated steel, offered from M6 to M16. This is the general purpose wedge lock nut, suited to structural steelwork, bridges and any bolted joint where vibration would otherwise back a conventional nut out.
• Nord-Lock Wheel Nuts: A fine pitched nut with a captive Nord-Lock washer pair in Delta Protekt® coated steel, offered from M16 to M24 at 1.5 mm pitch, plus a 7/8-11 BSF imperial option. The fine thread and heavier section suit wheel installation on trucks, trailers and heavy plant, where the washers simplify fitting and cut installation errors.

Where a captive assembly is not required, our full range of Nord-Lock washers offers the same wedge-locking action in a far wider spread of sizes, materials and finishes and can be paired with a standard nut. For less demanding joints that are not safety-critical, browse our locking nuts range, which resists vibration at a fraction of the cost.

FAQs

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

A: The purpose of a Nord-Lock nut is to lock a bolted joint using tension rather than friction, in a single captive component. It prevents the nut working loose under severe vibration, dynamic loads or operational shock, and because the washers are captivated it also removes the risk of an assembly being built with the securing washers missing or reversed.

Q: How do Nord-Lock nuts work?

A: A Nord-Lock nut works through the captive washer pair beneath it. Radial serrations grip the underside of the nut and the joint surface, while the cams on the inner faces interlock. The nut cannot turn without driving those cams apart, and every degree of attempted rotation adds clamp load instead of shedding it.

Q: What is the difference between Nord-Lock combi nuts and wheel nuts?

A: Nord-Lock combi nuts use a metric coarse thread with a zinc nickel plated finish and cover M6 to M16, which suits general structural and industrial joints. Nord-Lock wheel nuts use a metric fine 1.5 mm pitch thread with a Delta Protekt® coating and cover M16 to M24 plus 7/8-11 BSF, and are built for wheel fixings on trucks, trailers and heavy plant.

Q: Are Nord-Lock nuts reusable?

A: Nord-Lock nuts can generally be reused, reuse comes down to condition. If the teeth still stand proud, the cams are unmarked and the thread is sound, the nut can go back on. Anything with rounded teeth, scored cams or corrosion on the seating faces must get scrapped and clean threads are worth the minute they take.

Q: Are Nord-Lock nuts any good?

A: The locking performance is well proven and certified for European steel construction. What the nut adds on top is a practical benefit on top of the locking performance, since it speeds up assembly and cuts fitting errors.

Q: Nord-Lock nut vs a standard locking nut, which is better for vibration?

A: A wedge lock nut is significantly more reliable in high-vibration applications. Nylon insert and all-metal locking nuts resist rotation through friction and prevailing torque, both of which fade as the joint settles and the insert wears or heats. A Nord-Lock nut locks with tension and actively resists harder as the fastener tries to rotate. For light duty joints with minimal vibration, a standard locking nut remains the more economical choice.

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

A: Avoid Nord-Lock nuts where the contact surface is uneven, since irregularities stop the washer faces seating and bedding in properly. Soft metals and plastics are also out, because the teeth sink in and leave the joint sitting on a crushed bearing face rather than a gripped one and the captive format will not suit joints with no room for the additional nut thickness.

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

A: Nord-Lock nuts suit standard high-tensile bolts and studs matched by thread size and pitch, so check whether the joint calls for the coarse thread of a combi nut or the fine thread of a wheel nut. Two checks matter. The bearing face has to be able to take a bite from hardened teeth and the nut is taller than a plain hexagon nut, so confirm the thread engagement still works out.

Bespoke Nord-Lock Nuts Manufacture.

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