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Hand Tool Design
Submitted toDr. Engr. Mohammad IqbalProfessorIndustrial & Production Engineering,Shahjalal University of Science & Technology,Sylhet
Industrial & Production Engineering,Shahjalal University of Science & Technology
Submitted ByGroup B4Tanni Das 2013334054 Kyaw Zaw Thowai 2013334055Aminul Islam 2013334056K A M Shahrier 2013334057Mahbub Alam 2013334058Ali Akbar Tanim 2013334060
Industrial & Production Engineering,Shahjalal University of Science & Technology
and tool is any tool that is powered by . hand (manual labor) rather than by an engine.
Hand tool aid the Human forCutting, smashing, scraping, and piercing.Fit the work.Fit the user and hand.Not create injuries.
Hand tool design
H
Special Purpose Hand Tool
Industrial & Production Engineering,Shahjalal University of Science & Technology
Handled with power grip or with a precious grip. Small or large Flexible or, stiff One can design special purpose hand tool for specific task Possible to combine several hand tools into one.
Fig: A special Handtool
A tool use in multipurpose task at a time can be said as a specialHand tool. It saves time and make work easier.E.g. Hammer with an extension pulling nails, pliers with Hammer parts etc.
Hand tool designFitting the task
Power Grip The hand makes a fist with the forefinger on one side and the
thumb reaching around. It can be differentiate by direction of force i)Force parallel to the forearm. E.g. saw; ii) Force at angle to fore arm. E.g. Hammer iii)Torque about the fore arm. E.g. Screwdriver
Industrial & Production Engineering,Shahjalal University of Science & Technology
Saw
Hammer
Screw driver
Hand tool designPrecision Grip
Industrial & Production Engineering,Shahjalal University of Science & Technology
Internal Precision Grip The tool is held inside the hand. E.g. A table knife
External Precision Grip The tool is pinched by the thumbs . against the index finger and the middle finger. E.g. A pen.
Fig: Gripping a table Knife
Fig: Writing by pen
Hand tools and Power hand tools
Industrial & Production Engineering,Shahjalal University of Science & Technology
Hand Tools Power Tools
Hand tools are devices for performing work on a material or a physical system using only hands
Power tools are tools powered by an electric motor
Hand tools are propelled only by human power
Power tools always have a motor
Hand tools mechanism is very easy Power tools mechanism is not easy as hand tools
It is environment friendly and cheaper but take more time than power tools
Power tool save a considerable amount of time and effort in a larger project.
Hand tool Design For the User
Industrial & Production Engineering,Shahjalal University of Science & Technology
GoodPistol HandleVertical surfaceElbow height
BadPistol HandleHorizontal surfaceElbow height
BadStraight HandleVertical surfaceElbow height
GoodStraight HandleHorizontal surfaceElbow height
BadStraight HandleHorizontal surfaceBelow elbow height
GoodPiston HandleHorizontal surfaceBelow elbow height
Grip force vs Handle opening
Industrial & Production Engineering,Shahjalal University of Science & Technology
Fig: Maximum grip strength for male and female employees in electronics manufacturing
Hand -anthropometry
Industrial & Production Engineering,Shahjalal University of Science & Technology
Awkward situation Right handed tools for left handed users
create awkward situation. Awkward postures may cause to use more
force. Cut-outs for the fingers are responsible Awkward wrist position results in a loss of
strength It is responsible for CTD It affects torque exertion capability
Awkward wrist position (Terrell and Pursell-1976) :
Decreases grip strength by 12% Flexion/extension by 25% Radial/ulnar deviation by 15%
Prevention: Hand-tool should be designed both the
left handed & right handed user. Design hand-tools by hand
anthropometry Industrial & Production Engineering,Shahjalal University of Science & Technology
Injuries
Industrial & Production Engineering,Shahjalal University of Science & Technology
Cumulative Trauma disorder (CTD) Repetitive usage of hand tools Wear & tear on tissue on the joint. Vibration-Induced Injuries Hand tool vibration 1)Reynaud’s disease: Hand tool vibration in the frequency range 50-100 Hz 2)Dart’s disease: Vibration frequencies around 100 Hz
Reynaud’s disease
Industrial & Production Engineering,Shahjalal University of Science & Technology
2)Stiffness and numbness Reduction of blood flow Gradual loss of muscle control of the
hand
1)White finger disease Reduction in blood flow to the hand and
the finger
Fig: White finger disease
Fig: Stiffness and numbness
Industrial & Production Engineering,Shahjalal University of Science & Technology
Several Guidelines for Hand tools design
Aim:To increase operator comfort, convenience and controllability of hand tools .
Guidelines: For precision grip
Grip between thumb and fingerGrip thickness is 8 to 13 mmGrip length minimum 100 nmToll weight maximum 1.75 kgTrigger activated by distal phalanges of fingers with fast release mechanism.
Several Guidelines for Hand tools design
Industrial & Production Engineering,Shahjalal University of Science & Technology
For power grip
Grip with entire handGrip thickness 50-60 mmGrip length minimum 125 mmGrip force maximum 100 mGrip shape non-cylindrical Tool weight maximum 2.3 kg, 1.2 kg is preferableTrigger activated by thumb with locking mechanism
Several Guidelines for Hand tools design
Industrial & Production Engineering,Shahjalal University of Science & Technology
Grip surface smooth Slightly compressible and non conductive Avoid vibration, Particularly in the range of 50-100 Hz Design Handles for use by either handsKeep the wrist straight in the handshake orientationTool weight balanced about the grip axisEliminate pinching hazard