For over 30 years, Nord-Lock has provided safe, reliable bolting
solutions. More than just a range of products, the Nord-Lock Group
offers bolt securing systems to suit all needs and applications,
and are not only safe and reliable, but also cost effective.
Technical Training with Nord-Lock
We now offer technical training with Nord-Lock to meet your needs and solve the bolting challenges your applications face.
Since 1982, the Nord-Lock Group has been providing high quality solutions to an extensive range of industries. Nord-Lock are the trusted experts in bolt securing and optimisation.
Nord-Lock wedge-locking products are recognized around the world for their ability to secure bolted joints exposed to severe vibration and dynamic loads. The system cannot loosen unintentionally as it creates a wedge underneath the bolt head/nut. An ideal solution for bolted joints where failure is not an option.
In addition to Nord-Lock wedge lock washers, the range also includes wheel nuts, combi bolts and custom solutions.
How it works
Tension makes the bolt self-locking
Nord-Lock wedge-locking technology secures bolted joints with tension instead of friction. The system comprises of a pair of lock washers that has cams on one side and radial teeth on the opposite side.
Nord-Lock wedge-locking products positively lock the fastener in a joint which is subjected to extreme vibration or dynamic loads.
The key is the difference in angles. Since the cam angle " α " is larger than the thread pitch " β ", the pair of wedge lock washers expand more than the corresponding pitch of the thread.
The Nord-Lock Wedge-Locking Function
Tension makes the bolt self-locking
The rise of the cams between the Nord-Lock wedge lock washers is greater than the pitch of the bolt. In addition, there are radial teeth on the opposite side. The wedge lock washers are installed in pairs, cam face to cam face.
When the bolt and/or nut is tightened the teeth grip and seat the mating surfaces. The Nord-Lock wedge lock washer is locked in place, allowing movement only across the face of the cams. Any attempt from the bolt/nut to rotate loose is blocked by the wedge effect of the cams.
When a bolt is untightened with a wrench, the pair of washers expand more than the corresponding pitch of the thread allows the bolt/nut to rise. Nord-Lock wedge lock washers positively secure the fastener in a joint which is subjected to any kind of vibration or dynamic loads.
Video courtesy of the Nord-Lock Group
Benefits of using Nord-Lock wedge-locking solutions
- Maintains high clamp load and thereby ensures the function of the joint
- Quick and easy to install and remove with standard tools
- Locking function not affected by lubrication
- Defined and uniform friction conditions which result in a more accurate preload
- Same temperature characteristics as standard bolt / nut
- Reusable – in addition, Nord-Lock wedge lock washers do not affect the reusability of fasteners
- The washers are hardened and can support and distribute great loads
- Washers with enlarged outer diameter available for flanged bolts / nuts
- High corrosion resistance
- Can be used with fasteners up to grade 12.9 (ASTM A574)
- Reliable locking, even for joints with short clamp length
Proven in Junker vibration test
Nord-Lock locking washers are proven as a safe bolt securing system according to DIN 65151 tests performed by the independent research organisations IMA and CETIM. In addition, Nord-Lock personnel performs over 10,000 live Junker vibration tests around the globe every year.
The Junker test shows that Nord-Lock wedge lock washers safely secured the bolted connection; only a limited amount of tension is initially lost due to normal settlements. The wedge-locking function is verified through the clear increase in tension during untightening. All other bolt locking methods in the test failed to prevent loosening of the joint.
The Junker test, according to DIN 65151, is considered the most severe vibration test for bolted connections. During the test, the joint is exposed to transverse movements underneath the bolt head / nut, while the clamping force is continuously measured.
Proven according to NASM impact & vibration test
The National Aerospace test, according to NASM 1312-7, is a test method originally developed by the U.S. military to test bolted connections’ resilience against impact and vibration.
Nord-Lock wedge lock washers are proven as a safe bolt securing system according to NASM 1312-7 tests performed by the independent organisation Det Norske Veritas (DNV).
Drawing of the test rig. The assembled parts are vibrated vertically and the joints are subjected to two impacts per cycle. The impacts are parallel to the bolt. The arrow displays the direction of vibration during the test. After testing, the fasteners are inspected for rotation.
Multifunctional Wedge-Locking Technology
There are two main reasons why bolted joints fail: spontaneous bolt loosening and slackening. Traditionally, application design has involved trying to figure out which will have the biggest effect on the joint and choosing a solution to handle that one problem. It is a difficult compromise to make, especially when both could cause application failure.
Now, you can count on one solution to meet all your bolt securing needs. Introducing the new Nord-Lock X-series washers - for bolt security without compromise.
Bolt security without compromise
Utilizing a unique multifunctional design, Nord-Lock X-series washers offer the highest security against both spontaneous bolt loosening and slackening.
Nord-Lock’s multifunctional wedge-locking solution combine unrivaled wedge-effect to prevent spontaneous bolt loosening with an exceptional spring effect to compensate for loss of preload due to slackening, giving total security for those situations in which there can be no compromise.
The X-Series Principle
A new dimension of safety
Upon tightening the fastener, the washers flatten and the serrations engage the contact surfaces. Since the cam angle (α) is greater than the thread pitch (β), the wedge-locking effect will prevent any rotation of the fastener. Directly after tightening, the joint settles and the fastener sinks into the surface material. The washers immediately deflect and the spring effect (Fs) counteracts the slackening movement of the bolt, thereby preventing loss of preload on the joint.
These multiple functions continuously act on the bolted joint to maintain preload and prevent spontaneous bolt loosening — serving as an effective solution for vibration, dynamic loads, settlement and relaxation.
Benefits throughout your application’s lifespan
Below you find a selection of advantages with Nord-Lock multifunctional wedge-locking solution.
- Simplify design for demanding applications with a single solution that secures against both spontaneous bolt loosening and slackening.
- Save costs by using one solution for all bolt securing needs.
- Save time with quick and easy installation using standard tools.
- Facilitate inventory and logistical savings due to reduced item numbers.
- Achieve increased operational reliability while significantly reducing the risk of unplanned production stops, accidents, and warranty claims.
- Invest money and time in profit-generating tasks rather than retightening procedures.
- Decrease maintenance time with simple disassembly.
- Save time and money with a reusable solution, especially in industries with difficult access to the bolted joint.
Proven in Junker vibration test
The Junker test, according to DIN 65151, is considered the most severe vibration test for bolt connections. The test exposes the joint to transverse movements underneath the bolted head/nut, while continuously measuring the clamping force.
The Junker test shows that Nord-Lock’s wedge-locking function safely secures the bolted connection, which is verified through the clear increase in tension during untightening. The Nord-Lock X-series kept the highest initial tension thanks to its additional spring effect.
Nord-Lock personnel performs over 10,000 live Junker vibration tests around the globe every year.
Slackening and Vibration
The only solution that handles both loosening factors
To see how different products function in various circumstances, we can look at the evolution of preload in a bolted joint over time. The graph below illustrates the performance of traditional bolt securing products with composite materials. The diagram shows two phases: a static phase in which settlement is measured (over the period of 4 hours) and a dynamic phase when vibration is added (measured in 30 seconds). Compare how each of the solutions counteracts slackening and handles vibration.
Problems start as soon as the preload falls outside the functional range. If the preload is too high, yielding occurs. If it is too low, there is separation or sliding between the parts. Only Nord-Lock multifunctional wedge-locking solution keeps you within the optimal limits.
With the development of new materials and techniques - such as corrosion-resistant composites - slackening is a common problem due to settlement and relaxation.
Applications in heavy industries are constantly subjected to external forces, putting bolted joints at risk for spontaneous loosening due to vibration and dynamic loads.
Utilizing Superbolt technology, Nord-Lock is able to offer tremendous radial expansion and joint clamping power in one bolting system. The Expansion bolts replace traditional interference or force fit bolts. Radial expansion is critical for rotating couplings or alignment systems that require the bolts to be able to transfer forces in shear.
The key to this technology is the split expansion sleeve that mates with the customer’s machined holes. The split sleeve requires less tolerance on mating parts than is traditionally required with interference fit or hydraulic systems, saving critical machining time.
How they work
- Slide split tapered sleeve (2) onto the tapered stud (1) and place together in the bore.
- On side A, place spacer (3) in the bore to center split sleeve between the split line.
- On side A, slide washer over the tapered stud (1) and screw on the tensioner (4) by hand.
- Tighten jackbolts stepwise according to tightening procedure.
- On side B, slide hardened washer over the tapered stud (1) and screw on the tensioner (5) by hand.
- Tighten jackbolts stepwise according to tightening procedure
- Verify tensioner torque on side A.
- According to removal procedures, loosen the jackbolts on side A stepwise and unscrew the tensioner (4) by hand.
- Tighten several jackbolts on side B further, in order to release the tapered stud (1) off the tapered sleeve (2).
- Unscrew the tensioner (5) by hand.
- Remove tapered stud (1), tapered sleeve (2) and spacer (3) from the bore.
- Easy: Loose fit sleeves (up to .010″ – .020″ in the through-hole) are easily inserted even in holes misaligned due to rotation. Only hand tools are required for installation and removal.
- Fast: Tightening requires only minutes per assembly.
- Safe: Eliminates the need for special high powered tools, bolt deep freezing and high pressure hydraulic systems. Torque required is usually under 100 ft-lbs. Entire assembly requires only hand tools.
- Economical: Save money over hydraulic systems in time and tooling. No need to ream/hone the bolts as normal machine precision is sufficient. Additionally, for precise alignment as little as two Expansion Bolts can be sufficient. Loose fit through-bolts with MJT tensioners, can be used in the remaining holes.
- Reusable: The split sleeve springs back to original size, use after use. Compared to the close tolerance solid sleeves found in other systems, the loose fit split sleeve is much less likely to hang up during removal.
- Generates axial and radial force simultaneously. Easier to “pull together” coupling halves.
- No reaming/honing required: Only line boring of holes is necessary.
- No coupling face machining is required (where the nuts seat). The multi-jackbolt design compensates for small variations in perpendicularity of the spotface to the hole centerline.
- Eliminate finish machine of sleeves on site: Generous sleeve expansion permits finish machining in advance.