Application DataNord-Lock Washers
Applications
Nord-Lock washers cannot loosen unintentionally as a wedge-effect is created underneath the bolt/nut head. Our extensive range includes washers in various material and sizes.
Nord-Lock washers are available in two outer diameters - standard and enlarged. Washers with an enlarged outer diameter (over-sized washers) are ideal for use on large holes, sensitive surfaces and soft materials. Nord-Lock over-sized washers suit flanged bolts/nuts for optimum load distribution.
Advantages
° Nord-Lock original washers secure bolted joints exposed to severe vibration and dynamic loads
° Available in a wide range of materials to suit use in general steel and stainless steel applications, and in corrosive, acidic and high-temperature environments
° Locking function not affected by lubrication
° Achieves accurate preload with defined and uniform friction
° Available in a wide range of sizes (metric and imperial)
° Designed for steel bolts up to and including J429 Grade 8, alloy steel socket-head cap screws, and property class 12.9, and stainless steel up to and including grades A4-80, as well as strain-hardened grades of A193/A320 B8 & B8M
° High corrosion resistance (minimum 1,000 hours in salt spray test according to ISO 9227) for steel washers
° Reusable (depending on conditions of use)
° Custom sizes upon request
AN APPROVED SOLUTIONNord-Lock Washers
Tested and Certified
Nord-Lock washers are produced to the highest specifications and quality standards. They are rigorously tested throughout our production process and they have been approved by independent institutes as well as certification authorities. Nord-Lock washers are laser marked to ensure our customers receive genuine products and allows full traceability for every pair of washers.
High and Consistent Preload Control
The Junker test is the most severe vibration test for bolted joints. It is used to compare how different locking methods behave under transverse vibrations between two construction parts, while continuously measuring the clamp load. Working load is normally axial, shear load is transversal load. Preload is vital to keep parts together and prevent them from sliding — when lost a bolted joint will fail. During the Junker test (according to DIN 65151), the graph shows that the clamping load of all solutions drops dramatically apart from the Nord-Lock washers. All other solutions rely on friction, instead of geometry, to secure the bolted joint. Geometry is a more reliable locking method to control preload over time. This prevents costly downtime or potential accidents.
JOINT GUIDENord-Lock Washers
Tapped Holes
Nord-Lock washers safely lock the bolt against the underlying surface.
Counterbores
The outer diameter of regular Nord-Lock washers is designed for counterbore holes according to DIN 974, i.e. the washers fit under the head of standard bolts.
Through-Holes
As for all locking washers, through-holes require two pairs of Nord-Lock washers - one pair for securing the bolt and a second pair for securing the nut. Turn both fasteners in order to close the cams on both washer pairs before tightening to minimize settlements. Keep the nut secure while tightening the bolt.
Stud Bolts
Nord-lock washers safely lock the nut on stud bolts and eliminate the need for adhesives.
Applications with Large / Slotted Holes or Soft Underlying Surfaces
To optimize the load distribution for applications with large / slotted holes or with soft underlying surface, usa a flanged nut / bolt together with Nord-Lock over- sized washers with emlarged outer diameter.
Designs where Nord-Lock Washers are Not Recommended
- Mating surfaces that are not locked in place (see left figure)
- Mating surfaces harder than washers
- Very soft mating surface, e.g. wood, plastic
- Applications with extremely large settlements
- Non-proloaded joints
HOW IT WORKSNord-Lock Washers
TIGHTENING UNTIGHTENING
When the fastener is tightened, the cams lock and the serrations on the outer faces of the washers grip into both the fastener and the clamped part, creating clear impression marks in both. Clamping load has been created by the bolt, keeping the assembly locked in place.
Because the cam angle "A" is greater than the thread pitch "B" a wedge-locking effect secures the fastener against rotational loosening, even under the most severe conditions.
When the fastener is untightened, sliding will occur between the two washers. The upper washer is locked to the nut or bolt head by the serrations. The lower washer does not rotate as its serrations are locked into the surface being clamped.
As the cams slide over each other, the clamping load from the bolt is first increased as the bolt stretches, before being released as the cams pass each other.