Anti-Loosening Double Nut Bolt
Yuki Okimoto
Engineer department/Mechanical Engineer
NISSEI CO., Ltd.
Yamanashi-Ken, Japan
www.nisseiweb.co.jp

An invitation to look at a new solution
to the old bolt loosening problem andto not rely on the “friction”, but on the“Mecahnical Locking System”.

What is the PLB v2?

The PLB v2 has been designed to address the issues associated with the self-loosening of a bolted joint. By design,
the PLB v2 consists of a dual-thread screw shaft and twonuts of diﬀerent thread pitches. The ﬁrst, or big lead nut on
the shaft, is a multiplies-thread nut. The outer or secondary
nut on the shaft is a single-thread nut.

ISO16130 standard. Our lab tests have proven PLB v2’s outstanding self-locking features over 85% of remaining clamp
force that no other anti-loosening product oﬀers.

Exceptional Usability. PLB v2 can be tightened with one
action, whereas a standard double-nut type bolted joint requires two to three steps for tightening. No special tool isrequired. With the PLB v2, all you have to do is tighten theouter nut. The inner nut follows the outer nut and is tightenedalong with the outer unit.

As for double nuts assembly, vibration initiates loosening with the inner nut. With PLB v2, the inner nut's advanceis blocked by the slower-moving outer nut.
The mechanical lock is the secret to the PLB v2 Antiloosening design. No other fastener system in the world canmake this oﬀer. Most other anti-loosening kits use "friction"
for their anti-loosening function despite its uncertainty.
However, PLB v2 has a reliable solution.
PLB v2 locks the nuts with a “MECHANICAL LOCKING SYSTEM” that prevents them from loosening.

Main Features of the PLB v2

High Locking Performance. The vibration loosening
tests are conducted using a Junker test bench (J121, Vibrationmaster) in accordance with ISO16130. The relative residual clamp forces of all PLB v2 remain almost constantduring the vibration test. The ﬁnal rate of any residual clamp
force exceeded the reference value of 85% given in the92

Fastener Technology International/October 2021

The test was conducted per the following contents in accordance with the oﬃcial recommended working methods.
1. Insert and Tighten: Measure the time when the nut istightened with the speciﬁed torque.
2. Release: Measure the time to remove the tightened nut
from the bolt.
3. Re-tighten: Measure the time when the nut is re-tightened with the speciﬁed torque or more.
Most anti-loosening kits are diﬃcult to work with because they cannot be tightened/released with power or standard tools.
The PLB v2 can tighten/release with a power and standards tool, proving outstanding usability compared to thesame double nut type anti-loosening product.
Proved high tensile strength. We conducted the tensile
strength tests, which is an important mechanical property ofbolted joints. There are many products with ingenious screw
shapes, but few of them publish their tensile strength performance. The tensile strength tests of M12 PLB v2 and standard bolt and nut were conducted using the Autograph AG25TB, from Shimadzu Corporation. All these tests wereconducted three times under the same conditions; the sameresults were obtained in each trial. The red line shows thePLB v2, the black dashed line shows the standard bolt andnut, green horizontal line shows the yield point converted
to load (kN). PLB v2 oﬀers a tensile strength higher than
the yield point in all specimens as well as the standard boltand nut.
It is shown that the user can utilize the PLB v2 without
any practical problems.

High Reputation Received

Awards for technology innovations. The PLB v2 wasawarded the Technology Development Award (small andmedium-sized businesses) by JSTP in 2021. The title of thepaper was “Development of the world’s ﬁrst mass-produced
aﬀordable anti-loosening bolts using thread rolling process”,
in which the high performance of the PLB v2 and the production of PLB v2 thread rolling dies for mass production
were highly evaluated.
ThePLB v2 is the optimum product of Anti-loosening kitswith high technology.

Exhibited International Fastener Expo 2021

We, NISSEI CO., Ltd., exhibited PLB v2 at the International Fastener EXPO 2021 in Las Vegas, NV, USA. We
have received comments from various departments:
Manufacturers: Firstly, they have products like PLB v2
with the same materials and similar applications. This allows for these manufactures to grow their product oﬀerings,
without having to change their raw materials. Another reason they found PLB v2 attractive is the accessibility to thistechnology. Since NISSEI’s dies are made to ﬁt in a standard
threading machine, it takes less time to create PLB v2.
Distributors: They found the locking bolt system to be
intriguing because the durability of the product in conjunction with the myriad of applications for it. The long-lastinglocking bolt system is one that speaks for itself in the data.
As soon at distributors understood PLB v2’s value, they began imagining their customer who would be able to ﬁnd thisindispensable.
Industry expert: Those who have been in the industry
for a while were very intrigued by the Junker Test Graphthat was on the catalogue. The visual was an eﬀective comparison between PLB v2 and its competitors who have large
market share creating quite the impact.
Most visitors said they had never seen a mechanism suchas the dual threaded system. By touching the PLB v2, theyfelt and understood its outstanding performance. With thisbackground, we decided to provide the PLB v2 samples tothe user. And currently, we also look for the user to test thePLB v2 in the practical area that needs maintenance frequently. The user, who will test the PLB v2, can be provided
the PLB v2 from us for free-of-charge, up to 10 pieces. If
you have interested in it, please get in touch with us. For
further discussion, contact the author at NISSEI in Japan at
plb_bolt@nisseiweb.co.jp or visit www.nisseiweb.co.jp.
FTI
October 2021/Fastener Technology International93