Reason for choosing FUJILOK U-NUT



FUJILOK U-NUT was a groundbreaking Locknut introduced by Fuji Seimitsu as the first in the industry to feature a metal ring locking function. FUJILOK U-NUT sparked a revolution in the area of bolts and nuts where up until that point loosening had been considered unavoidable. It has passed over 50 years since the birth.
FUJILOK U-NUT is now the highly regarded as the first name in Locknuts across all industries from steel structures such as railways and connecting bridges to automobiles, motorcycles, and on up to industrial machines.

TOPWhat is FUJILOK U-NUTReason for choosing FUJILOK U-NUT

"Metal ring locking function" for the first in the industry

The FUJILOK U-NUT consists of a nut and friction ring (specialized spring). The friction ring is integrated with the top face of the nut by crimping.


"Locking effect" by Friction Ring

FUJILOK U-NUT is tightened on a bolt, the friction ring touches the bolt screw threads.
The friction ring then begins to bend along with the screw threads and press against the bolt screw threads.
Stress produced through a spring effect and Prevailing Torque (friction torque) caused by a reaction force that presses against the bolt thread are produced.
This will be locking operation.

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Reason for choosing FUJILOK U-NUT

  • Easy to install


    The same as general nuts, "FUJILOK U-NUT" is easy to install.

  • Heat-resistant


    As it is made of metal, it is not affected by heat as compared with nylon insert nuts.

  • Prevents nuts from quickly coming off


    Quick coming off can be prevented even if axial force drops. In addition, it is effective even in the middle position of the bolt.

  • Variety of shapes


    Various shapes are available, such as Cap Type U-NUT and Weld Type U-NUT.

  • Variety of size


    Thread sizes are from M3 up to M115. You can find your requested size.

  • Special order is available


    Production with special shape is also available.