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Ergonomic design of hammer handle to reduce musculoskeletal disorders of carpenters

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The musculoskeletal disorders (MSDs) are the most common work-related health problems in Bangladesh, affecting thousands of carpenters. Typically, musculoskeletal disorders affect the elbow, neck, shoulders and wrist pain during wooden work. The aim of this paper is to focus on certain important aspects of hammer use in occupational work situations, with an emphasis on comfort or discomfort in using hammer according to users. The study concluded that it was necessary to redesign the hammer to reduce the musculoskeletal disorders. Anthropometric data of 300 male carpenters (age: 45.23±11.65 years) in SouthWestern districts of Bangladesh were measured. The ergonomically designed multipurpose hammer reduces the musculoskeletal disorders mainly wrist pain 87% to 72%.
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International Journal of Research in Advanced Engineering and Technology
International Journal of Research in Advanced Engineering and Technology
ISSN: 2455-0876
Impact Factor: RJIF 5.44
Volume 4; Issue 2; May 2018; Page No. 78-83
Ergonomic design of hammer handle to reduce musculoskeletal disorders of carpenters
MT Haque1
1 Department of Industrial and Production Engineering, Jessore University of Science and Technology, Bangladesh
The musculoskeletal disorders (MSDs) are the most common work-related health problems in Bangladesh, affecting thousands of
carpenters. Typically, musculoskeletal disorders affect the elbow, neck, shoulders and wrist pain during wooden work. The aim of
this paper is to focus on certain important aspects of hammer use in occupational work situations, with an emphasis on comfort or
discomfort in using hammer according to users. The study concluded that it was necessary to redesign the hammer to reduce the
musculoskeletal disorders. Anthropometric data of 300 male carpenters (age: 45.23±11.65 years) in South-Western districts of
Bangladesh were measured. The ergonomically designed multipurpose hammer reduces the musculoskeletal disorders mainly wrist
pain 87% to 72%.
Keywords: hand tools, anthropomentry, musculoskeletal disorders, handle and power grip
1. Introduction
A hammer is a simple force amplifier that works by
converting mechanical work into kinetic energy and back [1].
Existing non-powered traditional hammer contains a head and
a handle, which can be fixed together by a special wedge or by
glue, or both. This construction is often used to combine a
compressed metallic striking head with a non-metallic shock
absorbing handle to reduce user fatigue from repeated strikes
[2-4]. Hammer is one kind of the best hand tool which todays
used for various function of household, machinery and
industrial works [5]. Hammer is one of the most important
hand tool used in carpentry. But an improper designed
hammer may cause significant musculoskeletal disorders
(MSDs) [6]. Musculoskeletal disorders (MSDs) are currently
most critical problems faced by the ergonomists in the
workplace [7]. Workplace injuries are extremely severe in
these types of industries. Poor working conditions and the
absence of workers have resulted in a very high incidence of
MSDs [8]. Ergonomically designed hand tools reduce the risk
of occupational disorders of the upper limbs. They also
provide comfortable work for the workers and give high
production rate [9]. Ergonomics is the scientific discipline
concerned with the understanding of interactions among
humans and other elements of a system, and the profession
that applies theory, Principles, data and methods to design in
order to optimize human well-being and overall system
performance [10]. Several researchers designed some non-
powered tools such as shovel, hammer, screw driver etc. In
that case they were focused on the comfort and discomfort
issues based on some parameter [11-17]. Grip size and diameter
is important parameter to design a hand tool. Proper gripping
improves the efficiency of the wooden work [18]. This study
was focused on hammer handle related injuries in traditional
carpentry or wooden work and controlling the rate of injury
through ergonomic study and designing new multi-purpose
hammer. In this study authors are trying to prevent the
ergonomic discomforts and injuries mainly wrist pain which
occurs most of the time using traditional hammer.
2. Methodology
A. Material and Methods
The study was conducted during 20th August 2017 to 20th
October 2017 in different areas of Bangladesh. In this study,
there were 300 carpenter’s respondents. All of them were
willing to participate in this study. A survey was conducted on
the types of hammers were used in Carpentry work. Following
figures-1 & 2 shows the design of hammers available in south-
western areas of Bangladesh [18-20].
Fig 1: (a) Carpenters hammer, (b) Bumping hammer, (c) Ball- peen
Carpenters hammer is a hammer with a cleft at one end for
pulling nails. Its broadly uses in carpenter industry. Bumping
hammer is a power-driven hammer with two broad flat faces
on a narrow head. It is used in bumping sheet metal. It is a
hammer have a rounded, hence “ball”, peen which used for
shaping metal closing rivets and rounding edges off metal pins
and fasteners. It is also used for hitting chisels and punches
during carpenter work.
International Journal of Research in Advanced Engineering and Technology
Fig 2: (d) Claw hammer, (e) Locksmiths hammer, (f) Masons
Claw hammer is a hammer with a heavy rigid head and a
handle. It is basically used to deliver an impulsive force by
striking. Locksmiths hammer is a German pattern hammer
with colored end of handle and basically handle made of
wood. Basically used to create high pressure & force.
Mansions hammer is a hammer with a moderately heavy head
sharpened at one end to a chisel edge. This types of hammer
specially used for removing pin from wood.
B. Measurement of existing hammers
The hammers are widely used in the carpentry and wooden
work in Bangladesh. Many existing hammers are not
ergonomically designed because they require a lot of wrist
bending and twisting during use. In this survey work
researchers took the measurement (Handle diameter, Grip
Size) of the different existing hammers shows in figure-3.
Fig 3: Measurements of hammers
C. Anthropometric measurements of hand
Hand length (HL): The length of the hand as measured
between the wrist crease and the tip of the longest finger on
the hand, usually thumb finger.
Hand breadth (HB): The length of the palm of the hand,
measured perpendicular to hand length.
Finger length (FL): The length of the thumb finger as
measured between the palmar digital and the tip of the middle
Hand breadth at metacarpal (HBM): The maximum breadth
across the hand where the fingers join the palm. The right
hand is extended straight and stiff with the fingers held
Fig 4: Hand anthropometry
D. Determination of an optimal cylindrical handle
diameter for power grip
In this study researchers use following equations to determine
the general grip, power grip diameter and grip size [21-29]:
…….... [1]
= ..... [2]
…….……….. [3]
E. Skewness test
According to Fan and Gencay (1995) [30], Hamilton (1989) [30-
31] following equations is used to calculate the skewness:
……………….... [4]
If the skewness is between the -0.5 and 0.5, the data are
approximately symmetric.
If the skewness is between -1 and -0.5 or between 0.5 and
1, the data are moderately skewed.
If the skewness is less than -1 or greater than 1, the data
are highly skewed.
3. Results
A. Ergonomic selection of musculoskeletal disorders
The Figure-5 and Table-1 presents the prevalence of
musculoskeletal disorders in different body regions of
carpenters. As Figure-5 shows, the most commonly affected
parts are wrist, shoulder and elbow.
Table 1: Frequencies of ergonomic discomforts and injuries
No. of
Percentage of
Workers (%)
Shoulder pain
Wrist pain
Stiffness in finger
Soreness in elbow
International Journal of Research in Advanced Engineering and Technology
In this study the prevalence of musculoskeletal disorders
among carpenters were 87% for the wrist pain due to improper
ergonomically designed hammer. Other musculoskeletal
disorders among workers were 72% for the stiffness in finger
and 75% for shoulder pain [32, 33].
Fig 5: Frequencies vs. Musculoskeletal Disorders (After using existing hammer)
Survey results shows that 69% carpenters want to improve in
working conditions, other result shows that more than 55% of
carpenters do not satisfied with their working environments.
47% workers want to redesign the hammer because of they are
not comfortable with exiting hammer. Most of carpenters
suffer from various musculoskeletal disorders which are not
good for long time, so that they want to improve the design of
their hammer [34-38].
B. Overall dimensions of hammers available in different
areas of Bangladesh
The overall dimensions of existing hammers were recorded
from different areas of Bangladesh show in following table.
Table 2: Dimensions of existing hammers
Handle length(cm)
Handle diameter(cm)
5th Percentile
50th Percentile
95th Percentile
C. Anthropometric measurements of the Carpenter
Table 3: Anthropometric measurements
5th %le
50th %le
95th %le
D. Skewness test of existing hammer
Table 4: Skewness test
Handle length (cm)
Handle diameter (cm)
Approximately symmetric
Highly Skewed
E. Proposed dimensions and design of ergonomically
designed hammer
Table 5: Proposed dimensions
Dimensions (cm)
Used Equations
Optimal grip diameter
Power grip diameter
Grip size
Fig 6: CAD Design (Isometric View)
International Journal of Research in Advanced Engineering and Technology
Fig 7: CAD Design (2D Drawing)
Fig 8: CAD design of newly designed hammer
F. Flexibility Analysis
Table 6: Ergonomically designed hammer vs. Existing hammer
Comfort factors
designed hammer
Quality of the hammer handle
Surface Finish of hammer handle
Compatibility for the type of grip
Overall Comfort at first look
Fits the hand
Effect of hammer use on hand/arm
G. Experimentation for ergonomically designed hammer
Table 7: Experimentation for optimal diameter
Grip size is too
The two middle fingers are digging into the
heel portion of the operator palm.
Grip size is
The two middle fingers are slightly gapped to
touching the heel portion of the operator palm.
Grip size is too
The two middle fingers have too much gap to
the heel portion of the operator palm.
The authors have found that the Grip size is correct and the
compatibility of grip is excellent. It fits with hand
I. Validation and Testing
The Figure-9 presents the prevalence of musculoskeletal
disorders in different body regions of workers after using new
designed multi-purpose hammer.
Fig 9: Frequencies vs. Musculoskeletal Disorders (After using new designed hammer)
4. Discussion
In this study, the authors survey different areas in Bangladesh.
Here the authors have found that the carpenters were facing
high level of wrist pain after carpentry or wooden work. For
this reason, the authors were recorded some significant
anthropometric measurements for purpose of designing
ergonomically correct hammer handle to prevent the wrist
5. Conclusion
The purpose of this study has been fulfilled; a hammer handle
for power grip operation has been developed and
implemented. However the workers found that their working
postures with new multipurpose hammer is good and reported
comfort. Results shows that wrist pain was the big of
musculoskeletal disorder of carpenters which have been
reduced to 72% from 87%.
6. Future Scope
In this study, anthropometric data were collected from 300
male carpenters of South-Western districts in Bangladesh. As
the scenario of wooden working condition in most of the
districts in Bangladesh is almost the same, the provided injury
and discomfort related data can be a great resource for the
administration and for social workers to understand the
working condition in carpentry industries of Bangladesh. In
International Journal of Research in Advanced Engineering and Technology
this study, research could not perform dynamic simulation of
hammer operation for lack of facility. It will be makes the
proposed hammer model more validate.
7. Acknowledgments
The authors are pleased to acknowledge Monir Ahmed,
Mahian Haque, Shamir Kumar, Shahinur Rahman and Nipen
Kar for their cooperation and assistance in conducting surveys
and collecting data in this study. The authors are also thankful
to Dr. Deepak Kumar Biswas (Assistant Surgeon, United
Health Complex, Jessore), Dr. Motiur Rahman (Assistant
Surgeon, Pirojpur Sadar Hospital, Pirojpur), and Dr. Siddharth
Kar (Assistant Registrar, Medicine, Jessore Medical College,
Jessore) for their help, support, and consultation through the
8. Conflicts of Interest
The authors declare that they have no conflicts of interest.
9. Ethical Statement
The authors declare that they have followed ethical
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... Although hammer can protect the bare hand from mechanical injury, improper use or poor design of the hammer in occupational work situations may introduce stresses through the hand-holding or operating it. That cause musculoskeletal disorders and injuries such as shoulder pain, wrist pain, soreness in elbow, stiffness in finger and headache [7]. ...
Manual hand tool design must meet all requirements making usable, safe and comfortable hand tool. An effective plan of design guidelines must define and implement all aspects of influence factors at the same time. Advances and innovativeness in tool design nominate complex geometry to achieve a better interaction between user and its tool. The goal of the paper is to create and evaluate an ultimate hand tool design preventing inefficiency and musculoskeletal disorders. A case study was conducted on the hammer.
... However, a workplace safety sheet reported that a good hammer has a rubber handle with pinch grip, which is generally more comfortable to use and produces greater force with the lower strain on the forearm, wrist and hand muscles, and ligaments and joints [23]. Furthermore, it has been proposed that handle length and grip size also affect pain in the hand among carpenters [24]. In addition, the workstation was managed by developing a tilting adjustable desk and stool for individual carvers, as a previous report showed a work station designed with a high seat that sloped forward by approximately 10 degrees in order to provoke anterior pelvic tilt [9,25] in industrial carpenters [11]. ...
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Purpose: To survey the work-related risk from wood carving and preliminarily assess the effectiveness of an ergonomic implementation program among wood carvers. Methods: A survey on musculoskeletal disorder (MSD) was conducted by using unstructured conversation, observation, and a focus group. The nature and opinion of the workers, using tools, work station, postures, environment and opinion on adapting to ergonomic factors were investigated and developed for an ergonomic implementation program. Work-related MSD was assessed by the Rapid Upper Limbs Assessment (RULA) at before and after implementation for three weeks. Moreover, the knowledge and, satisfaction on implementation program, and pain sensation were evaluated. Results from the survey result from 25 male wood carvers aged 45.76±8.3 years old showed that. The size, dimension and design of the devices affected to MSD. Most of the wood carvers had low back pain. After ergonomic program was implemented by educated and trained in 14 wood carvers, the knowledge score improved significantly, except total RULA and total pain scores of all regions. But the RULA and pain scores at low back region showed significant improvement. Conclusion: Low back pain was predominantly in wood carvers and a specific ergonomic implementation program can improve posture and reduce pain. Keywords: Ergonomic; Wood carving; Work-related musculoskeletal disorder
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