Rolling a Low-Cost Lock Bolt
by:Shuichi Amano
Chief Engineer/Engineering Director
Nissei Co., Ltd.
Yamanashi Prefecture, Japan
www.nisseiweb.co.jp

An invitation to look at a new solution to theold problem of bolt loosening — request toroll and sell it under a licensing arrangement.

We might think there are no technical improvements left
to be made on a bolt. But let’s think again—what about theproblem of loosening? It is a fact of mechanical life thatbolts loosen. Many techniques for keeping bolts tight haveappeared. From the point of view of practical usage, cost effectiveness and the ability to truly prevent loosening, making
better bolts is an old, but new problem.
Nissei invites you to look at its fresh solution, the PLBv2.
PLBv2 (Perfect Lock Bolt, version 2) relies on double nuts
and multiple threads rolled onto a single shaft.
For fasteners such as bolts, loosening is the enemy. The
need for periodic tightening and problems arising when bolts
need to be replaced or re-used is common. In the battle against
loosening, many solutions have been attempted—all, until
now, mediocre. Relying on friction to prevent bolts fromloosening is not good enough. A mechanical solution built
into the structure of the bolts is what is needed.

Principles and Features of PLBv2

Here is one mechanical method to protect against loosening. Roll the lead of each bolt with two diﬀerent threads,
then add one nut to follow each thread. Because the leadthat the inner nut follows is bigger than the one for the outernut, when vibration inevitably makes the nuts start to rotateloose, the inner nut will be blocked by the outer nut. This isbecause the lead followed by the outer nut is more closelypacked, and so the outer nut must rotate more slowly. This ismechanical blocking.
High Lock Performance
The lock bolt that Nissei has developed and named PLBv2
has been tested and conforms to international standard
ISO16130. For the speciﬁed vibration criterion relative residual clamp force of 2000 cycles, other companies’ products
received a rating of “Acceptable loss of clamp force”, which
in ISO16130 terms means they perform adequately from 85%
at best to 40% of the time. PLBv2 is rated ISO16130 “Goodself-locking behaviour”, meaning performance is good 93%of the time.
Practicality & Ease of Use
A major value of PLBv2, above and beyond its lock properties, is practicality in actual use. By tightening the outer nut,
the inner nut is also tightened. Both nuts, one action. With
ordinary double nuts, each nuts must be tightened individually.
With PLBv2, the inner nut follows the outer nut naturally. It islike having to fasten only one nut instead of two. No PLBv2speciﬁc tools are required, ordinary tools do the job. Ease andpracticality in usage are additional advantages of PLBv2.
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Manufacturing Method

How to mass produce bolts with two separate and distinct
threads? It cannot be done reliably by cutting threads into thebolt shaft, but it can be done with thread rolling. Nissei, aninnovative maker of rolling machinery located in Yamanashi
Prefecture in Japan, has tackled this problem to produce
uniform and reliable bolts that cannot be loosened by normal
vibration: PLBv2.
Machines that could make dies capable of rolling a complicated pattern were not readily available when we started
our Perfect Lock Bolt project, in 2018
we used round dies, then in 2019 wetried plane-type ﬂat dies, developing
new techniques one after the other.
By 2020, our focus was on shortening
the time it takes to make the bolts. We
envisioned planetary dies as the means
to this end. All in all, it has taken
15 years to reach the level at which
our machines can roll two kinds ofthreads—simultaneously—on one lock bolt.

Evaluation Tests

Nissei have tested to quantitatively evaluate the combinedresults of lock performance and workability under ISO16130,
which are important for users to use.
Testing Machine: Junker Test Bench(J120T, Vibrationmaster)
Test Fastener Speciﬁcations
Nominal designation of thread: M12
Material: AISI-4135
Strength class: 10.9
Vibration Test Conditions
Frequency: 12.5
Amplitude: ±0.8
Lubricant: Rust inhibitorIn conclusion, the PLBv2 oﬀers a signiﬁcant reduction inlabor costs due to its superior lock performance and ease ofuse compared to standard screws and other company’s antiloosening products.

Do You Want To Be a PLBv2Producer in Your Area?

Vibration Test Procedure
1. The test is conducted with a torque value of
42 Nm and a number of load cycles (N=2500).
2. Measure the initial axial force at the point of thereference torque of 42 Nm, and end the testwhen the force is 40% or less of the initial axialforce.
3. Measure the number of load cycles at the endof the test.
The test results show that the PLBv2 did not loosen until
12290 cycles while the standard bolt loosened after 74 cycles.
In other words, we can evaluate that the PLBv2 can save 166times of retightening compared to the standard bolt.
Another major diﬀerentiating factor is that the PLBv2 hasmore than 80% residual axial force for up to 10000 cycles,
whereas other company's anti-loosening products show asigniﬁcant drop in residual axial force after 2500 cycles ofvibration.
The table above also shows the results of multiplying thenumber of retightening cycles based on PLBv2 by the timeand number of bolts to be retightened (50 pcs).
It is clear that the PLBv2 contributes to a signiﬁcant reduction in maintenance costs compared to standard bolts.

Nissei is not a bolt manufacturer, but a machine manufacturer of cylindrical die form rolling machines.
We can manufacture and sell PLBv2, but we have no experience in selling bolts. Therefore, it takes a lot of preparation
for sales development.
In order to spread this safety assurance technology aroundthe world as quickly as possible, we have decided to adopt
a business model where we do not mass produce and sell
PLBv2, but provide bolt manufacturers with the license tomanufacture and sell it.
Bolt manufacturers can use the optional form rolling diesrented from us to manufacture PLBv2 in the same process asnormal bolts with their existing production facilities.
Therefore, there is no need to introduce new machinery,
and initial costs can be reduced.
For Further discussion, contact the author at Nissei in Japanor visit the company's website.
https://www.nisseiweb.co.jp/e/products.php?page=plbv2
FTI

Company Proﬁle:As form rolling professionals, Nissei Co., Ltd., a Japan-based a joint-stock corporation, specializes inform rolling. Nissei takes pride in developing formrolling technology as the backbone of 21st century
industry. The company will continue to raise the bar
to the highest standards, and in so doing, contribute to society through win-win relationships with its
clients. The company manufactures and/or sells thefollowing brands of form rolling machines: Comet,Galaxy and Aries. The Nissei slogan is “Make eachday’s work sparkle with joy and excitement.”
www.nisseiweb.co.jp
February 2021/Fastener Technology International

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