6Torque Tools are
Measurement
Equipment

6-1. Torque Tools are Measurement Equipment(1) Control of torque tools─── 76(2) Calibration of torque tools ─── 76

6-2. Traceability(1) Traceability system ────── 77(2) Diagram of torque traceability andNational standard ──────── 78(3) ISO 9000-related documents ── 80

6-3. E n g a g e m e n t w i t h J C S S a n ddevelopment of services(1) JCSS outline ───────── 81(2) JCSS calibration service ──── 82(3) Flow of JCSS calibration ──── 84

6-4. Accuracy and Uncertainty(1) Accuracy ─────────── 85(2) Uncertainty ───────── 86(3) Analysis procedure for
uncertainty in measurements ─── 88(4) Example of uncertainty ──── 89(5) Accuracy of torque tools ─── 91(6) Durable accuracy of torque tools(Tohnichi standards) ────── 92

6-5. Tool control(1) Tool Control ───────── 93(2) Select testers──────── 93(3) Testers for torque tools ──── 94(4) Standards of Tohnichi, ISO, JIS(ISO 6789, JIS B 4652) ───── 94(5) Naming of hand torque tools ── 95(6) Cautions for calibration of hand torque tools 95

74

TOHNICHI TORQUE HANDBOOK Vol.8

TECHNICAL DATATorque Tools as Measuring Equipment
Main measuring equipment
Dial indicating torque wrench

Digital torque screwdriver

Caliper※

Chapter
Digital micro meter※

Dial gauge※

6Torque Tools are
Measurement Equipment* Provided from Mitutoyo

Measurement Control in ISO 9001: 2008 (Extract)
Human resource

▲

6.2.2

Competence, awareness and traininga） Determine the necessary competence for personnel
performing work aﬀecting product quality.
b） Provide training or take other actions to satisfy these needs.
c） Evaluate the eﬀectiveness of the action taken.
d） Ensures that its personnel are aware of the relevance andimportance of their activities and how they contribute to theachievement of the quality objectives.
e） Maintain appropriate records of education, training, skills, andexperience.

Measuring equipment▲

7.6

Control of monitoring and measuring devices.
Where necessary to ensure valid results, measuring equipment
shalla） be calibrated or verified at specified intervals, or prior
to use, against measurement standards traceable tointernational or national measurement standards.
b） Provide training or take other actions to satisfy these needs.
c） be identiﬁed to enable the calibration status to be determined.
d） be safeguarded from adjustments that would invalidate themeasurement result.
e） be protected from damage and deterioration during handling,
maintenance and storage.
In addition, the organization shall assess and record the validity of the previous measuring results
when the equipment is found not to conform to requirements.

Technical Data

75

Chapter

6-1

Torque Tools are Measurement Equipment

Torque Tools are Measurement Equipment（1）Control of torque tools
The process for controlling torque tools (Figure 6-1) involves

accuracies. The periodic calibration cycle depends on theascertaining the accuracy by adequately checking thesame factors, but normally this is set between 3 months andmeasurement of the tools upon reception at the facility anda year. If possible this cycle should be readjusted as the tool

on a daily basis. The decision of how to set up the process forages to allow more eﬀective control.

the control should assess the following factors: importance,

Due to torque tools are precision measurement equipment

usage frequency, and usage torque capacity of the measuringcontrast to standard hand tools, take care for storage

instruments, by referring to the ISO standards (ISO 6789),

and management to maintain accuracy and durability.

JIS standards (JIS B 4652), and the manufacturer s nominal
Figure 6-1. Control system for torque tools
Selection of
Torque Wrench

TEL
FAX
E-mailTOHNICHI
Reference and support materials
Product guide
Torque handbook

ReturnTohnichi website
Technical materials

Traceability chart

Order

Sales support
Torque seminar
Parts list

DeliveryParts supplies

Exhibition/Laboratory

Customer

Torque = Force x Length, it is requiredthat the reference standard used in
the calibration should use weights forlength. The reference standard being

AcceptanceOK

Certiﬁcate ofcalibration
Outer company
Inner company

Registration

Work

used as the standard for testing othertorque tools should be three times
more accurate than the item being
tested. Therefore, to calibrate a torque

Inner company
ControlWork

Because torque is expressed as

the force and a scale or calipers for theNG

Outer company（2）Calibration of
torque tools

tool with a 1% accuracy rating, a better
Spare tools

Use

Storagethan ±0.3% rated reference standard
must be used. The reference standard
must then be periodically calibrated by

OK

Regular calibration OK
and inspection
NG

Daily inspection

NG
OK

Repair/Adjustment/
Inspection

an oﬃcial organization to maintain theiraccuracy and traceability.

*Example: Once a year

NG
Disposal76

TOHNICHI TORQUE HANDBOOK Vol.8

6-2

TECHNICAL DATA

Chapter

Torque Tools are Measurement Equipment

Traceability
Chapter（1）Traceability system
precise standard equipment and the standard equipment also

on the traceability system (Figure 6-2). Services, such as

calibrated by a higher level of standard devices. Eventually,

calibration and repair, are very important and necessary factors

it chains to National standard and when it certified, it can bein the control process. All of these services required for internal

described as traceable for National standard. Torque can becompany controls of torque tools, such as inspection sheets,

resolved into length by the force. As the units of length andcalibration certificates, and traceability charts (Figure 6-3),

force are approved by oﬃcial calibration laboratory respectively

are available upon request. Use the Traceability Issue Request

these units, or in part of country, torque itself chains directory toforms from Tohnichi agents and included with the generaloﬃcial calibration laboratory.

product information for such traceability requests.

Figure 6-2. Traceability of Tohnichi products

Figure 6-3. Traceability chart

National Institute of Advanced
Industrial Science and Technology (AIST)

Measuring
Measuring Calibration InstituteCalibration InstituteLengthMass
TorqueWorking Standard

Mass

Calibration Lever

Weight

Force

Force

Force

Technical Data

Bolt Tension Meter

Torque Meter

Torque Gauge

Power Torque Tool

Torque Screwdriver

Torque (tester)

Torque Wrench

Tohnichi Products

LengthTorqueMeasuring
Calibration Institute77

6
Torque Tools are
Measurement Equipment

Tohnichi is producing a wide variety of torque tools based

Reference Oﬃcial calibration
Standard
Laboratory

Generally, measurement equipment will be calibrated with more

Chapter

6-2

Torque Tools are Measurement Equipment

Traceability（2）Diagram of torque traceability and National standard
In order to secure traceability system using torque SI units, the establishment of calibration methods using national torquestandards is quickening worldwide. In Japan, a supply system using national torque standards has been prepared, in which
torque meters that measure pure torsion are already being supplied in a range of 5 N・m to 20 kN・m, and reference torquewrenches that occupy the top standard of torque wrench testers are being provided in a range of 5 N・m to 5 kN・m. Items
from the technical requirement application principles to the torque level structure for torque meters and reference torquewrenches disclosed by National Institute of Technology and Evaluation (NITE) shows in the ﬁgure 6-4. The layer composedof torque wrench and torque screwdriver and chains to torque tester and checker is "Tertiary Stage", the layer chains toreference torque wrench and reference torque screwdriver is "Secondary stage", and the layer chains from torque calibration
machine to designated secondary standard equipment is "Primary stage".

Figure 6-4. Traceability System Diagram

Torque Standard Machine

Designated Secondary Standard Equipment

Torque Measuring Device

Reference Torque Wrench

Torque Calibration Machine

Torque Meter Calibration Machine

Torque Wrench Calibration Machine

Torque Meter

Reference TorqueScrewdriver

Reference Torque Wrench

Torque Testing
MachineTorque Screwdriver
TesterTorque Screwdriver Torque Wrench Torque Wrench
CheckerChecker
Tester

Reference Torque Wrench

Object for Secondary stage calibration

Object for Tertiary Stage Calibration or Test

Secondary Stage

Tertiary Stage

Primary Stage

Torque Standard Machine

Torque Screwdriver

Torque Wrench

Apply the word "Calibration" to primaly stage and secondary stage, label "Test" for tertiary stage. "Test" is ineligible for JCSS.

78

TOHNICHI TORQUE HANDBOOK Vol.8

TECHNICAL DATA

■Designated standard equipment … Equipment designated as the national standard that realizes
the torque units.
(Torque standard Machine)
Chapter

Reference torque wrench calibrated using the designatedstandard equipment

standard equipment. In addition to realizing the reference(Reference torque wrench)

standards relating to the calibration company s torque, this isused for maintenance and control of calibration equipment.

This is an actual loading type, load cell type, or build-up type
(Torque wrench calibration Machine) torque wrench standard tool used for direct comparison
calibration of the reference torque wrench, the calibrationequipment, by the primary stage calibration company.

■Working standard …

■Regular reference standard …
(Reference torque wrench)■Torque wrench tester

Among the torque measurement equipment, this indicatesa tool with a torque wrench shaped sensor part (torqueconverter) provided with a lever that certainly conveys thetorque together with the side force and bending moment.
This is a tool for calibrating (or testing) torque wrenches, and isequipment that realizes torque using a torque loading device. It is used
for calibrating by reference torque wrenches to chain higher standards.

Using these, through the establishing of a torque supply system by JCSS (refer to 6-3.), a traceability system fortorque will be established similar to that for other units.
However, outside the torque ranges provided, local calibration will be required using [Force x Length = Torque](Assembly unit) as before. In addition, because the level provided by JCSS is only up to the secondary level, it willbasically only cover up to torque wrench testers and torque screwdriver testers.
It is expected that torque wrenches and torque screwdrivers will be transferred and have their calibration based on the
JIS B 4652 standard as described below.

Establishment of Hand Torque Tools - Requirements and Test Methods (JIS B 4652) Standard
Following the progress in establishing the torque supply system described above, it was required to prepare standards
for manual torque tools because the contents of the previously used JIS B 4650 standard for manual torque wrenches
mainly gave stipulations regarding torque wrench product speciﬁcations, resulting in the following problems:
１）The standard only covered torque wrenches, with no stipulations for torque screwdrivers.
２）There were many speciﬁcations relating to manufacturing according to models and materials, and the method of
calibration was unclear.
３）
The standards had not been agreed to conform with international standards.
Here, the international standard ISO 6789: 2003 (Assembly tools for screws and nuts. Hand torque tools.
Requirements and test methods for design conformance testing, quality conformance testing and recalibration
procedure) was translated and submitted by the Japan Measuring Instruments Federation as the Japanese industrial
standards, and this was established as JIS B 4652 on April 20, 2008.
Technical Data

79

6
Torque Tools are
Measurement Equipment■Designated secondary …

Chapter

6-2

Torque Tools are Measurement Equipment

Traceability（3）ISO 9000-related documents
Torque equipment is also required to be controlled, calibrated and have traceability withnational standards as a measurement instrument according to ISO 9000. Tohnichi
provides certiﬁcate of calibration shown in Figure 6-5. Alternatively, upon the customers request, we also issue an inspection certiﬁcate, traceability chart shown in Figure 6-6.
Tohnichi stores the histories of these issued documents for a certain period and it helps
maintain your torque management system base on ISO 9000.

Figure 6-5. Certiﬁcate of calibration supplied with torque wrenches

Figure 6-6. ISO Related document

1. Calibration Certiﬁcate(Combined with inspection certiﬁcate)

2. Inspection Certiﬁcate
3. Traceability Chart

80

TOHNICHI TORQUE HANDBOOK Vol.8

6-3

TECHNICAL DATA

Chapter

Torque Tools are Measurement Equipment

Engagement wit JCSS and development of services

As of November 2011, Tohnichi Accredited Room registered as an authorized calibration
service provider of JCSS Secondary stage.

（1）JCSS outline

Chapter

6

Figure 6-7. JCSS symbol

consists of the National standards provisionsystem and the Calibration laboratory
accreditation system introduced by the amended

Torque Tools are
Measurement Equipment

Japan Calibration Service System (JCSS)

0281

Measurement Law enforced in November, 1993.
Under the JCSS of calibration laboratory

Figure 6-8. JCSS symbol with MRA compliant

accreditation system, calibration laboratories
are assessed and accredited as Accredited
Calibration Laboratories to meet the requirementsof the Measurement Law, relevant regulations
and ISO/IEC 17025. International Accreditation

0281

Japan (IAJapan), NITE, plays as the accreditationbody of JCSS and conducts accreditation
process with the system conforming to ISO/IEC
17011 and relevant international criteria.
JCSS, Accredited Calibration Laboratories
meet the requirements laid down in the
Measurement Law as well as those of ISO/IEC 17025.
Calibration certiﬁcates with the above JCSS
symbol issued by Accredited Calibration
Laboratories assure the traceability to
National Measurement Standards as well
as a laboratory's technical and operational
competence and are acceptable in theworld through the ILAC and APLAC MRA.
（ Reference Material Producers meets therequirements of ISO Guide 34:2009 andISO/IEC 17025:2005）
Extract from National Institute of Technology and Evaluation (NITE)Technical Data

81

Chapter

6-3

Torque Tools are Measurement Equipment

Engagement with JCSS and development of services（2）JCSS calibration service
The following diagram figure 6-9. is traceability chart toa reference torque wrench on the JCSS system. The calibration

National standard from a perspective of torque wrench.

certificate that issued by accredited calibration laboratories

Secondary stage torque category that Tohnichi has been

under the JCSS system has JCSS symbol and MRA compliant

registered applied the torque range from 10N・m to 1000 N・msymbol on the certificate and certify the torque to be traced

of torque wrench tester shown in ﬁgure 6-10., is calibrated bydirectly to National standard shown in ﬁgure 6-11.

Figure 6-9 Traceability chart from the view point of calibration service
Torque Wrench

Torque Wrench Tester

Reference Torque Wrench

JCSS calibration with areference torque wrench

Torque Wrench Calibration Machine

Calibration of reference torque wrenchby torque wrench calibration machine

Designated Secondary Standard Equipment

Designated Secondary Standard Equipment

Torque Standard Machine

Torque Standard Machine(Provided from AIST)82

TOHNICHI TORQUE HANDBOOK Vol.8

TECHNICAL DATA
Figure 6-10 JCSS certiﬁcation of registry and MRA attestation certiﬁcation(Registration the torque range from 10 N・m to 1000 N・m)

Chapter

Torque Tools are
Measurement Equipment

6

Figure 6-11. Example of JCSS calibration certiﬁcate (Initial page only)Technical Data

83

Chapter

6-3

Torque Tools are Measurement Equipment

Engagement with JCSS and development of services（3）Flow of JCSS calibration
Figure 6-12 shows a flowchart of JCSS

Under JCSS calibration system, not only

calibration system. Application form is sent

newly purchasing Tohnichi torque wrenchin advance to confirm requirements.

testers, also being used tester can be"Tohnichi Accredited Room" performs

calibrated. Contact Tohnichi for further

calibration.

information.

Figure 6-12

Flow of JCSS calibration

User

Tohnichi Dealers

Tohnichi Accredited Room

Request（TEL、
FAX、
E-mail）
Initial check and sending application form

Fill out application
form

Conﬁrmation

Request New Purchasing
Quotation
Contact the user
Dispatch Testers

Receiving Goods
Inspect Goods
Acknowledge

Quotation

Ordering
JCSS Calibration
Ordering new tester

Receiving Goods

84

Delivery of Goods
with Certiﬁcate

Issue Certiﬁcate

TOHNICHI TORQUE HANDBOOK Vol.8

6-4

TECHNICAL DATA

Chapter

Torque Tools are Measurement Equipment

Accuracy and Uncertainty
Chapter（1）Accuracy

Accuracy is the overall favorable condition including the correctness and precision of values shown by measuring equipment or measurement
results. Further, correctness is the condition where there is little deviation, while precision is the condition where there is little dispersion.

6

True value

True value

Measured value

Residual
Deviation

X
（a）

X
（b）

X
（C）

Case where dispersion issmall, but there is deviation

Case where deviation issmall, but there is dispersion

Case where there isdeviation and dispersion

Error
Bias
Correction

Table 6-1. Glossary of terms used in measurement(Extracted from JIS Z 8103, Glossary of terms used in measurement)

Term

Deﬁnition

True value

Value consistent with the deﬁnition of a given particular quantity. (refer to Figure 6-14)
Remarks: Excluding particular cases, this is an ideal value it is unattainable practically.

Measuredvalue

That value which has been obtained by a measurement. (refer to Figure 6-14)

Error

That value subtracted by the true value from a measured value. (refer to Figure 6-14)
Remarks: The ratio of an error to the true value is called the relative error. However, in the casewhere it is not liable to be confused, it may also be called simply an error.

Bias

A subtracted value of population mean of measured value by a true value. (refer to Figure 6-14)

Deviation

A subtracted value by population mean from a measured value. (refer to Figure 6-14)

Residual

A subtracted value by sample mean from a measured value. (refer to Figure 6-14)

Value added algebraically to the uncorrected result of a measurement to compensate for systematic error. (refer to Figure 6-14)
Rem arks：1. The correction is equal to the negative of the estimated systematic error.
2. The ratio of the correction to the read out value or calculated value is called the correction rate,
Correction
and the value of correction rate expressed in percentage is called the percentage correction.
3. For the purpose of compensating the presumable systematic error, the factor to be
multiplied to the measured result before correction is called the correction factor.
Dispersion

Unevenness of the magnitudes of measured values. Otherwise, the degree of irregularity.
Remarks: In order to express the magnitude of dispersion, for example a term of standard deviation is used.

Technical Data

85

Torque Tools are
Measurement Equipment

Accuracy = Deviation + Dispersion
Deviation: In graduated torque measuring devices, this is the difference between the graduated values and the measured values. In torquemeasuring devices without graduation (preset type), this is the diﬀerence between the set torque value and the measured torque value.
Dispersion: The standard for the dispersion is taken as 2σ or 3σ.
True value
Population mean
Figure 6-14.
Sample mean
Figure 6-13. Relation between deviation and dispersion
Relation of
measured value
Deviationand true value
Deviation
True value

Chapter

6-4

Torque Tools are Measurement Equipment

Accuracy and Uncertainty（2）Uncertainty
Without assuming the conventional concept of the true value (which is generally unknown), the uncertainty is
obtained from the data dispersion (already known) in the data range, using the measured results themselves.
(Figure 6-13) The methods of evaluating uncertainty are classiﬁed under the following two types:① Evaluation method by statistical analysis from a series of measured values.
(Uncertainty type A)② Evaluation method by a means other than statistical analysis from a series of measured values.
(Uncertainty type B)
Further, for both of type A and type B, the standard uncertainties and the standard deviations (or similarvalues) are estimated from the normal distribution, rectangular distribution and trapezoid distribution.
Finally, these are combined by the propagation rule of errors. (The combined standard uncertainty)
Under these procedures, the overall uncertainty is indicated as the Extended Uncertainty.

Table 6-15. Factors for uncertainty in general measurements
Measurement method

Measuring device

Work piece

Measuring environment

Measurement principle(Rules, deﬁnitions)
Measuring period

Measuring person

Measurement time

Table 6-9. Uncertainty

Generally within the range of 2σ (k = 2)
96

97

98

99

100

Measured value
99.3
98.34

86

101

102

103

Uncertainty
0.96

100.26TOHNICHI TORQUE HANDBOOK Vol.8

TECHNICAL DATA

Chapter

In normal distribution, σ (standard error) equals the standard uncertainty and generally, 2σ equals the extended
uncertainty. In rectangular distribution, dividing the half width of distribution (a) by 3 equals the extended uncertainty(a/ 3). In triangular distribution, dividing the half width of distribution by 6 equals the standard uncertainty (a/ 6).

6

Normal distribution
σ Standard uncertainty

Triangular distribution

Rectangular distribution

2σTorque Tools are
Measurement Equipment

Table 6-17. How to estimate the uncertaintyaa

σ=a/ 3

σ=a/ 6

Extended uncertainty

To obtain the resolution of a digital display for the uncertainty of 1 [digit], dividing 0.5 [digit] (half the width of 1 [digit])by 3 equals the standard uncertainty (1 [digit]/2 3). For example, if the resolution (Nmin) using the minimum torquecapacity (Tmin) is taken as 100, 1 [digit] equals 1% and the uncertainty of its resolution (Udigit) equals 0.29%.

Table 6-18. Example of estimating the uncertainty from the rectangular distribution

Resolution of digital display
Uncertainty for 1 [digit] (Udigit)
Resolution Nmin at Tmin
Udigit = 1/(Nmin × 2 3) ×100%
1/resolution × 100%
Nmin
100
200
400

Technical Data

Udigit
0.29%
0.14%
0.07%

1[digit]
1/resolution × 100%uu
1[digit]/2 3

87

Chapter

6-4

Torque Tools are Measurement Equipment

Accuracy and Uncertainty（3）Analysis procedure for uncertainty in measurements① Setting the method of measurement and calibration. (Describe the procedure concisely.)
Describe the principles and measuring methods, measuring devices and instruments concisely.
② Construction of the mathematical model (Write the formulas or state the principal factors.)a）Describe the formulas if they can express the uncertainty.
b）If the uncertainty cannot be expressed by numerical formulas, indicate the factors of theuncertainties and combine them by adding.
c）
Execute the test of significance through experiments based upon the design ofexperiments and factor analysis. Then estimate the uncertainties of each factor.
③ Correction of values (Describe the correction items and the methods, if any.) If corrections
are made, the estimation of uncertainties should be carried out after the data correction.
④ Analysis and estimation of uncertainty elements (Including type A and type B classification) point out andclassify the uncertainty elements, and estimate the standard deviation (or similar values) per element as follows:a）Uncertainty of standard. (Described as the standard uncertainty.)b）The uncertainty compared to the standard. Uncertainty resulting from factors such as
the calibration equipment, calibration environment, calibration period, work piece, etc.
(Described in the standard uncertainty; show the basis of the method of determination).
⑤ Calculation of combined standard uncertainty (Square root of sum of squares)
n

1

／
2

uc =（Σui2） =i＝1

u12＋u22＋…un2(The apparent differences between type A and type B will disappear.)⑥ Calculation of extended uncertaintyu = k・uc
k: Coverage factor(Generally, k = 2 is taken. If not, describe the reason for this.)88

TOHNICHI TORQUE HANDBOOK Vol.8

TECHNICAL DATA

Chapter（4）Example of uncertainty① Theoretical formula
Torque [N·m] = Mass of dead weight [kg] x Gravitational acceleration [m/s²] x Eﬀective length of calibration lever L [mm]

DOTCL100N・Torque wrench tester

DOTE100N3

Torque Tools are
Measurement Equipment② Hypothetical models
・Torque calibration kit③ Uncertainty of calibration of torque wrench tester
Extended uncertainty of torque calibration kit: UIA
Extended uncertainty of torque calibration work: UIB
Extended uncertainty of measured torque: UIT (UIT² = UIA² + UIB²)
Extended uncertainty of torque wrench tester: UC
Extended uncertainty of calibration of torque wrench tester: UT (UT² = UIT² + UC²)
④ Uncertainty of torque calibration kit
Factors
・Mass (standard dead weight)

Standard uncertainty
0.0004%・Mass for measurement 0.01%
・Gravitational acceleration

Combined standard uncertainty for force

uf =0.00042＋0.012＋0.0052＋0.0152＋0.0142 = 0.023%

0.005%＊(Refer to P. 23, ''Acceleration of gravity'')・Corrections of speciﬁc gravity 0.015%
・Vertical/horizontal conversion 0.014%
・Scale (calibration)

0.006%

・Length of lever(process tolerance) 0.02%
・Diameter of wire

0.02%

・Elongation of lever

0.014%

Combined standard uncertainty of length of lever

ul =0.0062＋0.022＋0.022＋0.0142 = 0.032%

Combined standard uncertainty of torque calibration kit

ua =uf 2＋ul 2 =0.0232＋0.0322 = 0.04%

Extended standard uncertainty of torque calibration kit (k = 2)

UIA = 2×ua = 0.08%

Technical Data

6

89

Chapter

6-4

Torque Tools are Measurement Equipment

Accuracy and Uncertainty⑤ Uncertainty of torque calibration
Factors

Standard uncertainty

・Horizontality of wire

0.06%

・Inclination of lever (horizontality)

0.06%

・Length of lever (angle of drive)

0.03%

・Newton conversion

0.03%

・Repeated uncertainty

0.1%

Combined standard uncertainty of torque calibration work:ub =0.062＋0.062＋0.032＋0.032＋0.12 = 0.14%

Extended uncertainty of torque calibration work:

UIB = 2×ub =0.28%
Extended uncertainty of calibration torque:UIT =UIA2＋UIB2 = 0.29%⑥ Uncertainty of calibration of torque wrench tester
Factors

Standard uncertainty

・Resolution of torque wrench tester (zero point)

0.06%

・Resolution of torque wrench tester (display)

0.06%

・Friction of axis bearing area

0.005%

・Uncertainty of gauge

0.14%

・Uncertainty of display

0.14%

Combined standard uncertainty of torque wrench tester:uc =0.062＋0.062＋0.0052＋0.142＋0.142 = 0.22%

Extended uncertainty of torque wrench tester:UC = 2×uc =0.44%
Extended uncertainty of calibration of torque wrench tester:UT =UIT2＋UC2 = 0.52%⑦ Traceability of torque tools
The extended uncertainty of the torque wrench tester is required to be below ±1% (k = 2).
The extended uncertainty of the torque of the torque calibration kit should be below ±0.3% (k = 2).
Therefore, the standard uncertainty of the calibration kit is expected to be below 0.15%.
Each standard uncertainty of inferior characteristics that is below 0.015% can be ignored.

90

TOHNICHI TORQUE HANDBOOK Vol.8

TECHNICAL DATA

Chapter（5）Accuracy of Torque Tools
wrench or torque screwdriver is being carried

As（%）＝

out using a measuring instrument. Match theindicated value on the index of the graduatedAs(%)： Calculated deviation of the torque toolscale of the measuring instrument being

Xa : Indicated Value of torque toolcalibrated with the measuring point, and read

Xr : Reference Value (Calibration Equipment)

the numbers on the measuring instrument.

Calculated value from torque tool deviation＝Indicating Value of torque tool − Measuring Value of Calibration Equipment
Measuring Value of Calibration Equipment

Indicated Value of torque toolCalculation example

As ＝（χa−χr）
×100
χr

As（%） χa ＝50×100

Reference Value (Calibration Equipment)χr ＝52（50−52）×100＝−3.85%52

Idea of Tohnichi product accuracy is reading each values thatdifferences between indicating value and measuring value.

R

D

%

F.

S
.

Figure 6-19 shows that concept of each Reading (RD) and

3
＋

3

%

＋

Measured value

Figure 6-19. Diﬀerence in accuracy between RD and FS

Full Scale Values (F.S.).
In case of F.S. 3% accuracy, 3% difference of high value
point is covered all measuring points. In contrast, reading 3%means against each measuring points.

−

3

%

F.

S

.

−

3%

RD

Reference value

Technical Data

91

Torque Tools are
Measurement Equipment

6

Situation where calibration of a torqueChapter

6-4

Torque Tools are Measurement Equipment

Accuracy and Uncertainty

Table 6-2. List of Torque Equipment Accuracy
Description

Model Name

Digital Torque Wrench Tester

TF、TCC、DOTE

Digital Torque Meter

TME

Digital Torque Screwdriver Tester

TDT

Digital Torque Wrench Checker

LC

Digital Rotary Torque Checker

ST

Digital Torque Screwdriver

STC

Accuracy± 1％＋ digit

Digital Torque Wrench

CEM、CTA、CTB

Digital Torque Gauge

ATGE、BTGE

Torque Meter

TM

Torque Gauge

ATG、BTG

Torque Wrench Tester± 2％ +1digit

± 2％

DOT

Digital Torque Wrench

CPT

Torque Screwdriver

RTD、LTD、NTD、FTD、MTD、RNTD、A/BMRD、
A/BMLD etc.

Torque Wrench

QL（E）、CL（E）、DQL（E)、TW、SP、QSP、PQL、
MPQL etc.

Semi-automatic Torque Wrench± 3％

A、AC、DACTorque Wrench
Power Torque Tool

± 1％

QSPCA12N 〜 70N± 4％

U、UR、AUR、AP、DAP、ME、MC、DCME、HAT etc.

± 5％

QSPCA6N± 6％

Torque Wrench（6）Durability Accuracy of Tohnichi Standard■Manual Torque Tools■Power Torque Tools

Guaranteed 100,000 cycle operations at maximum torque

Guaranteed 500,000 cycle operations or one

value or one year from the ﬁrst use under proper operation.

year from the ﬁrst use under proper operation.

With proper calibration, adjustment and parts replacement

Required periodical calibration and overhauling.

if required, on every 100,000 cycles, torque wrenches
up to 420N・m models can be used 1,000,000 times,
up to 1000N・m models 500,000 times, and more than
1000N・m models 250,000 times.

92

TOHNICHI TORQUE HANDBOOK Vol.8

6-5

TECHNICAL DATA

Chapter

Torque Tools are Measurement Equipment

Tool Control
Chapter（1）Tool Control
Any torque equipments break down and cause malfunction as they are used for a long time.
To prevent it, periodical check and calibration are required.

6

Periodic Calibration : To control accuracy of each torque equipments
Table 6-3. Daily Check and Periodic Calibration

Inspection of Accuracy

Self-Management
Daily check by operators

Central-Management
Regular Inspection at Repair/Accredited Room

Torque Degradation

Early detection leads to prevent a big defects production.

Detection of defects on periodic time.

Possible to prevention
Click Torque Wrench and Power Torque Tool
Torque Wrench Checker
Worker
Accuracy Check and Replacement
Tool room Check Torque Wrench Testers, Adjustment and Repairing

Using until they break down.
Indicating Torque Wrench
Torque Wrench Testers, DOT/DOTE/TCC/TF
Replacement
Inspection all tools, Adjustment and Repairing

Malfunction
Applicable Type
TesterCorrespondence（2）Select Testers
Checker for Daily Check … Not using loading device, operated by hand, there is possibilities to beaﬀected by loading position, speed and direction.

Tester for Calibration … Operated on loading device, calibration values are stable.

Table 6-4. Select Testers
Type
ArticleChecker
LC

ObjectTorqueWrenchAccuracy± 1%+1digit

Torque Range
AnalogDigitalManualPower
Direction

Technical Data

Tester
ST

DOT

DOTE

TF, TCCPower Tool,
TorqueTorque Wrench Screwdriver

TorqueWrenchTorqueWrenchTorqueWrench

± 1%+1digit± 2%± 1%+1digit± 1%+1digit

Small-Medium-Large Small-Medium-Large
×
×
○
○
○
○
×
×
Right
Right/Left

TDT± 1%+1digit
Small
×
○
○
×
Right/Left

Small-Medium Small-Medium-Large Small-Medium-Large
○
×
×
×
○
○
○
○
○（TCC）○（DOT-MD）○（DOTE-MD）
○（TF）
Right
Right/Left
Right/Left

93

Torque Tools are
Measurement Equipment

Daily Check : To prevent a large number of defect productChapter

6-5

Torque Tools are Measurement Equipment

Tool Control（3）Testers for torque tools
Table 6-5. Example of Torque tools and Testers/Checkers

Torque tools

Representative Model

Tester / Checker

Pneumatic screwdriver
Semi-automatic airtork
Fully automatic airtork
Multiple unit
Manual torque screwdriver
Manual torque wrench
Tester, Checker, Torque meter

U、
UR、AUR
A、
AC、DAC
HAT、AP、DAP
ME、
MC、
MG、
DCME
RTD、LTD、AMRD、BMRD
QL、SP、QSP、TW、QSPCA
DOTE、LC、
TF、TDT、TME

TCF＋TP＋Display
DOT・DOTE・LC・TF・TCC Torque wrench tester
TCF＋TP＋Display、
ST
TCF＋TP＋Display、
ST
TDT、
ATGE、
TCF＋Display
DOT・DOTE・LC・TF・TCC Torque wrench tester
Calibration kit (weight + calibration lever/pulley)（4）Standards of Tohnichi, ISO, JIS (ISO 6789, JIS B 4652)
Table 6-6. Permissible deviation of torque value
A. Dial indicating
type
B. Adjustable
type

Tohnichi standard
ISO、JIS standard
Tohnichi standard
ISO、JIS standard
Tohnichi standard

C. Preset type

ISO、JIS standard

Wrench、Screwdriver
WrenchScrewdriver
Wrench、Screwdriver
WrenchScrewdriver
Wrench、Screwdriver
WrenchScrewdriver± 3%
Below 10 N·m ± 6%
Above 10 N·m ± 4%
± 6%
± 3%
Below 10 N·m ± 6%
Above 10 N·m ± 4%
± 6%
± 3％※
Below 10 N·m ± 6%
Above 10 N·m ± 4%
± 6%

Permissible deviation of JIS, ISO sectionalize by the maximum torque range of torque tools.

※QSPCA is based on ISO and JIS standard

Table 6-7. Measurement procedure
A. Dial indicating
type
B. Adjustable
type

C. Preset type94

1. Tohnichi standard
2. ISO standard
3. JIS standard
1. Tohnichi standard
2. ISO standard
3. JIS standard
1. Tohnichi standard
2. ISO standard
3. JIS standard

Preliminary loading at maximum capacity → Release loading →Zero adjustment → Measure 5 times at each measuring point
5 times preliminary loading at maximum capacity → Measure 5 times at
each measuring point
5 times preliminary loading at torque set value → Measure 5 times

TOHNICHI TORQUE HANDBOOK Vol.8

TECHNICAL DATA

Table 6-8. Measurement point

B. Adjustable type
C. Preset type

Tohnichi standard
ISO、JIS standard
Tohnichi standard
ISO、JIS standard
Tohnichi standard
ISO、JIS standard

20%
60%
100% ※of maximum torque value

Chapter

Torque set value

6※In case of lower limit of the measurement range is less than 20%of the maximum torque of torque tool, Tohninichi standard also measures at that point.

（5）Naming of hand torque tools
Table 6-9. Naming of torque tools
Type I Indicating type torque tool (ISO, JIS)Class AClass BClass CClass DClass E

Twisting or deﬂection beam type wrenchHigh rigidity housing type wrench with scale, dial, or display unit
High rigidity housing type wrench with electronic indicator
Screwdriver with scale, dial, or display unit
Screwdriver with electronic indicator

Class AClass ＢClass ＣClass ＤClass ＥClass ＦClass Ｇ

Variable torque type wrench with graduations or display unit
Fixed torque type wrench
Variable torque type wrench with no graduations
Variable torque type screwdriver with graduations or display unit
Fixed torque type screwdriver
Variable torque type screwdriver with no graduations
Deﬂection beam / variable torque type wrench with graduations

Type II Adjustable type torque tool (ISO, JIS)

Tohnichi equivalent model

F、
CF
DB、CDB、
T
CEM
FTD
STC
Tohnichi equivalent model

QL、CL、PQL
QSP、CSP、QSPCA−
LTD、RTD
NTD、RNTD−−（6）Cautions for calibration of hand torque tools
Common items

Type I
Indicating type
torque tools

Type II
Adjustable type
torque tools

Calibration
DeviceCalibration
Temperature

The maximum permissible uncertainty of the calibration equipment:
measurement should be ±1% of the indicated value. (including coeﬃcient k = 2)
Should be in the range of 18 to 28°
C and should have a temperature variationof less than ±1°
C. (The maximum relative humidity should be 90%)

Installation

Within ±3%, applied force within ±10°
, screwdriver gradient within ±5°.

Preliminary
Loading
Loading
MethodCarry out preliminary loading one time up to the maximum value in the working
direction, and set to zero after releasing the load.
Load gradually with increasing force until the indicated torque value is reached.

Installation

Tilt within ±3%, applied force within ±10°
, screwdriver gradient within ±5°.

Preliminary
Loading
Loading
MethodCarry out loading ﬁve times to the maximum capacity (torque tool nominal
capacity) in the working direction, and carry out averaging.
After loading gradually with increasing force up to 80% of the target torque value, slowly
apply a ﬁnal loading evenly over 0.5 to 4 seconds to reach the target torque value.

Technical Data

95

Torque Tools are
Measurement Equipment

A. Dial indicating type