TOPProduct InformationFINE U-NUTFINE U-NUT


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  • 製品名

With FINE U-NUT, unlike lockwasher, variable positioning at the appropriate location is possible and torque management is also easy. This groundbreaking lock nut for use with bearings makes unnecessary of machining key ways on shafts, lockwashers, and a high degree of skill for installation. FINE U-NUT improves the rotational balance of bearings that provide power in all machine industries. Reduction of equipment rotation loss and reduction of power consumption are also realized.



・ Machining of key ways on shafts is unnecessary.

・ No lockwasher is required, which removes the possibility of the lockwasher being incorrectly installed.

・ Assembly does not require a high degree of skill.

・ Fine adjustment is possible and torque management is easy.

・ Shaft rotational balance is improved.

・ Can be reused.



M8~M100 (SS series)

M10~M150 (SC series)

M10~M100 (SUS series)

※Pitch: Extra fine thread

Stainless Spring Steel Friction Ring

270°Friction Ring


Grooved round nut ※ Other special shape


Thread Accuracy:JIS6H(Old JIS class 2)

Maximum face runout (Max.): 0.05 (M8~M50)

Maximum face runout (Max.): 0.07 (M55~M120)

Maximum face runout (Max.): 0.10 (M125~M150)


SS400 or equivalent = low carbon steel,

S45C (heat-treated) = high carbon steel (H.T.),

SUS304 or equivalent = stainless steel 304 (A2)

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The friction ring touches the shaft screw threads, and stress (P) is produced through a spring effect when the nut is tightened as shown the figure. Along with a reaction force (P'), a frictional torque (prevailing torque) that presses against the shaft screw threads and prevents free rotation is produced.


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Prevailing torque is the frictional torque that is produced by the Friction Ring acting on the shaft screw threads.



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Axial impact vibration test

Test Conditions




Smaple size M20×1
Tightening torque 53.9N・m{550kgf・cm}



Specification of testing machine

Frequency 1.278c.p.m
Excitation stroke 11mm
Impact stroke 10mm
Vibrating acceleration of excitation table 10G
Excitation time 60 minitues
Direction of impact Bolt axis direction


Test Result



Rotation Life Test

Test Conditions

Sample size


Speed of revolution


Testing cycle

1cycle (Forward raotaion, Stop, Reverse rotation, top) 10 sec.

Stopping time

For forward rotaton : 0.30 sec.

For reverse rotation : 0.27 sec.



Inertial force applied to the nut during stopping


Inertial force Nmkgfcm
For forwad rotation For reverse rotation
Standard bearing nut

0.14 { 1.42 }

0.15 { 1.69 }
FINE U-NUT 0.15 { 1.52 } 0.17 { 1.69 }

Test result

Sample Sample No,1 Result of endurance test

Standard nut



1 Washer damaged and nut came off at approx. 110,000 cycles.
2 Washer damaged and nut came off at approx. 330,000 cycles.


3 No change after 500,000 cycles.


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    1. Apply lubricant after checking that the tip of the thread portion of the shaft has a chamfer that is equivalent to the distance of 1 pitch. When the shaft has low hardness, use lubricant with especially high lubricating properties.

    2. Manually screw the nut on until the friction ring touches the tip of the thread portion of the shaft. ※ The nut cannot be installed from the friction ring side.

    3. Confirming friction ring has contacted the shaft thread.

      Using a hook wrench is also OK.
      High-speed rotation impact wrenches cannot be used.

    5. Press down on the axis portion of the ratchet handle and tighten by lightly turning the ratchet.


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This product is used for especially safety position.
Observe strictly the following items when using.

  • Use bolts with a chamfered tip with ISO 6g (Class 2) thread accuracy.

  • Use lubricant where problems such as scorching or seizing may occur during installation and remove of a nut.

  • For full locking, ensure that two full shaft protrude beyond the friction ring at the top of the FINE U-NUT.

  • Face runout values listed in the size table are valid only for when tightening is performed to at least 2 times the prevailing torque.

  • FINE U-NUT cannot be used if the shaft thread is machined with a keyway or other processing.

  • The nut cannot be installed from the friction ring side.

  • Stop using the nut if excessive deformation or another fault is found on the Friction Ring and the clamp.

  • Impact wrench cannot be used.

  • If use under severe conditions or with low axial tension, consult us.