WHAT ARE HARDLOCK NUTS?
HARDLOCK NUT RESISTS LOOSENING UNDER ANY CIRCUMSTANCE
The HARDLOCK NUT (HLN) has a structure that prevents looseness through a traditional Japanese wedging principal. To effectively utilize the wedge structure, two nuts are used, a convex nut and aconcave nut, which fit together by wedging against one another.
When the nuts wedge together, it creates a powerful locking effect not just to each other but to the bolt shaft, achieving the anti-
loosening effect. Once locked with this powerful force, the HARDLOCK NUT is impervious to impulsive forces or shocks.
FEATURES OF HARDLOCK NUTS
HARDLOCK NUTS HAS CONDENSED THE BEST OF ENGINEERING
Unparalleled rotation loosening prevention
Screw position can be fixed at any position
Fully reusable with welding equivalent locking
Bolt preload sustained permanently
EXPERIMENT VIDEOS
The highest quality product based on the national standard tests
JUNKER LOOSENING TEST
In this test, vibration is applied to the bolt axis to loosen the fastener. This test is compliant with the German Institute of Standardization (DIN) 65151.
NAS Test
The Aerospace Industries Association (NAS) test evaluates the looseness prevention that is determined by the US aerospace standards.
TIGHTENING TORQUE TEST
Our torque testing equipment is specifically designed to evaluate the torque and torque coefficient of the concave and convex nuts utilized in our “HARDLOCK Nut” products, ensuring the utmost safety and reliability.
Tensile Strength Test
This test is fundamental in the material science and engineering in which a sample is subjected to controlled tension until it fails.
PRIMARILY MEASURING EQUIPMENTS
No Compromise to Achieve the Highest Quality Nuts
CNC/Contour Measuring Machine
By Mitutoyo
Handy probe 3D Measuring Machine
By KEYENCE
Digital Microscope
By KEYENCE
Manual CMM
By Mitutoyo
Image Dimension Measuring Machine
By KEYENCE
Hardness Tester
By Mitutoyo
1000X
Based on Finite Element Analysis (FEA), the HARDLOCK Nut has 1,000 times of more self-locking effect than general hex nuts.
WHAT OUR CLIENT SAYS
“We adopted HARDLOCK Nuts for a construction project. HARDLOCK Nuts have achieved secure fastening for over 10 years, and we were able to reduce our maintenance costs. We highly recommend HARDLOCK Nuts for your next projects.”
Japan Highway Public Corporation
H.Yanagawa | Project Manager
FREQUENTLY ASKED QUESTION
Got questions about the HARDLOCK Nut? We Have Answers.
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The HARDLOCK Nut is a self-locking nut developed by HARDLOCK Industry through a process of trial and error as an elegant solution to the technical question: “Can the wedge principle be employed for the purpose of loosening prevention?”
In general, forcing a wedge into the gap between a cylinder and its surrounding tube makes it possible to create a powerfully locked assembly (as shown in the figure).
Likewise, creating matching key grooves in both a nut and a bolt, and then using a hammer to drive a wedge into those grooves can be used to produce a powerful self-locking effect. However, this method is unsatisfactory from the standpoint of operability.
The solution employed in the HARDLOCK Nut is to use two nuts to play the roles of the hammer and wedge respectively. A small eccentricity in the sliding part of the convex top surface of the lower nut acts as the wedge. When the upper nut with its concave bottom surface is tightened, the effect produced is exactly the same as that produced by a hammer driving in a wedge. Moreover, it is much more effective to use a screw as this makes it very easy to drive the wedge into place.
This is because when fastened, the HARDLOCK Nut produces stress both in the direction of the axis and in a direction perpendicular to the axis. Firstly, the convex fastening nut generates axial torque in the same way as a normal nut.
Then, as the concave lock nut is tightened, the wedge effect generates stress perpendicular to the axis, which pushes the convex nut against to the screw thread. When the concave nut is completely tightened, the HARDLOCK Nut produces a stable self-locking force by means of the combined stresses of P1 + P2 + P3 (in the figure above), with the result that it remains unaffected by the external vibration or impact.
The HARDLOCK NUT can be used in a wide range of locations including:
• Locations subject to harsh impacts and/or vibration
• Locations where joints are welded or bonded but it is necessary to remove them for maintenance or servicing
• Important locations where post-installation maintenance not feasible
• Dangerous locations involving a hazard to human life
• Locations subject to extreme temperature variations
• Locations where very strong fastening is not possible
• Locations in extremely tough environments
In principle, the HARDLOCK NUT can be reused many times. The actual suitability for reuse will depend on the environmental conditions of previous use, but as long as the nut’s material has not deteriorated or been excessively deformed, its self-tightening performance will not decline.
When considering reusing a nut, remove the concave portion, and then manually screw it in until it touches the convex portion. As long as there is a gap of about one pitch between the two, they can be used again. If there is not an adequate gap, the concave portion may undergo a plastic deformation, rending it unfit for further use.
