Name of the experiment: Study and design of different types of hand tools (Pliers)
Introduction:
Tool used by hand is a hand tool. Hand tools basically extend capability of the hand. Greater
capability can be more impact, more grip, more torque or even new functions. For designing a
hand tool, Pliers are selected to study. Pliers are hand tool used to hold objects firmly, for
cutting, bending, or physical compression. The design principles are grouped into General
Principles, Grip Principles, Precision Principles and Geometry Principles.
Objectives:
To study ergonomic principles in designing of hand tools.
To observe the existing hand tool.
To design hand tool using ergonomic principles.
To eliminate the existing shortcomings.
Methodology:
1. The major components, their functions, dimensions and the relative positions of the hand
tool with hand or palm were identified.
2. The tool was operated for a typical job to understand the interaction with the handle to
hand grip.
3. The working postures of the body were observed carefully and the interactions between
the body and different part of the tool were observed too.
4. A survey was done with 40 people for noting down the general
feeling of the user and for taking the anthropometric measurements of hand gripping and
others.
5. From the above mentioned steps shortcomings of Geometry, dimension, alignment,
material, and shape etc. of parts of the tool that were not designed ergonomically
resulting in discomfort and risk of musculoskeletal disorders from long time use were
identified with certain reasons.
6. An improved design explaining with modifications and a neat sketch was proposed for
better hand-tool interactions.
Pliers:
Pliers are a hand tool used to hold objects firmly, for cutting, bending, or physical
compression. The objects can then be turned, bent, or otherwise manipulated. Generally,
pliers consist of a pair of metal first-class levers joined at a fulcrum positioned closer to one
end of the levers, creating short jaws on one side of the fulcrum, and longer handles on the
other side. Pliers have parallel handles, a pivot where the handles join, and parallel jaws that
grasp the object. Special-use pliers may have additional components and purposes, such as
cutting pliers. This arrangement creates a mechanical advantage, allowing the force of the
hand's grip to be amplified and focused on an object with precision. Types of pliers include
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engineer's pliers for gripping metal, flat-nosed pliers for grasping smaller objects, electrician's
pliers for gripping electrical wires, and round-nosed pliers for bending wire into loops. The
most common are slip joint pliers and plumber's pliers, both with slip-joint adjustments to
change the width of the jaw grip.
Fig 01: Pliers
Different Parts of Pliers:
Pliers have three main parts that all work together to produce a smooth tool.
1. The Handle
2. Joint Portion
3. Head Portion
1) The Handle: The handles of a pair of pliers typically have an ergonomic design to facilitate
proper gripping that won't cause damage to the fingers and hand.
2) Joint Portion: The joint portion of pliers is the pivot point; it must operate smoothly without
obstruction, allowing the pliers to open and close with just the pressure from one hand.
3) Head Portion: The head portion of a pair of pliers can be designed for gripping or cutting.
The head has a tip; a jaw just below the tip; a gripping surface, which usually has ridges; a pipe
grip, which is the central portion of the head; and side cutters at the bottom of the head.
Dimensions of Pliers:
The dimensions of pliers differ because there are so many types available. Some of the most
common pliers’ sizes are 6 inches, 8 inches and 10 inches. But there are other sizes inches, 8
inches and 10 inches.
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Fig 02: Dimensions of Pliers
Length Coverage
Model Tip shape Tip thickness
(mm) (mm)
E 348 175 Bent 1.8φ 19～65
Pliers with Several Unique Properties:
Rubber coated handle for a firm and powerful grip
Soft shapes minimize the risk of damage
Well-placed joints with excellent compound action and control
Precision hardened cutting edge for the best cutting performance
Hard-wearing return spring for enhanced comfort
ISO certified production meets the stringent cutting and load requirements of the
ANSI and DIN standards.
How to Maintain & Safely User a Pliers:
Quality pliers are maintenance-free and can last a decade or more if not abused. Locking and
other special-purpose pliers may require additional maintenance to adjusters, springs, or the
release lever.
To safely use pliers, first it should be determined which type of pliers is required for the job.
Then, adjustments needed to be made to the slip joint, if any. Locking pliers may require
adjustment before use. The jaw should be closed around the object by pressing the handles
closer together. The tool should be rotated as needed to bend or turn the object. For safety, it is
needed to make sure that fingers and skin are not pinched by the handles, pivot, or jaw.
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Survey Questions on Pliers:
A questionnaire on Pliers
:Name :Gender
:Age :Occupation
1. How often do you use pliers?
(i) Daily.
(ii) Weekly
(iii) Monthly
(iv) Yearly
.2Why do you use the Pliers?
(i) Household work
(ii) Construction
(iii) Local business
(iv) Industrial use
.3What type of Pliers do you use usually?
(i) Slip-joint pliers.
(ii) Fixed joint pliers.
(iii) Linemen’s Pliers.
(iv) Diagonal Pliers.
.4Approximately how long do you use pliers each time?
(i) A few seconds
(ii) A few minutes
(iii) 5-15 minutes
(iv) 15+ minutes
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.5What should be the size of Pliers?
(i) Small
(ii) Medium
(iii) Large
.6What should be the length of the pliers?
(i) 5-10 inch
(ii) 4.5-8 inch
(iii) 4-6.5 inch
(iv) 7-10 inch
.7 What should be the weight of Pliers? (In gm).
(i) 100-140
(ii) 180-140
(iii) 220-180
(iv) 350-220
.8Pliers should be made by which material?
(i) Aluminum
(ii) Mild steel
(iii) Cast Iron
(iv) Steel
.9When buying pliers, would the design aesthetics influence your purchase choice?
(i) Yes
(ii) No
10. What type of grip (with rubber) of Pliers do you prefer?
(i) Smooth Grip
(ii) Knurled Grip
11. Do you face any problem while using it?
(i) Yes
(ii) No
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12. Which part of Pliers is causing the problem?
(i) Parallel handle
(ii) Serrated jaw
(iii) Rod gripping section
(iv) Side cutter.
13. What should be the desired lifetime of Pliers with respect to price?
(i) Low lifetime- Low price
(ii) Medium lifetime- Medium price
(iii) High lifetime- Medium price
(iv) Very high lifetime- High price
15. What is the acceptable price for the Pliers? (BDT).
(i) 150
(ii) 200
(iii) 300
(iv) 400
16. Have you ever injured yourself using pliers? If yes explain how.
Ans:
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Weight of the tool
It is best to limit the weight of the tool to 2 pounds (1kg) or less for tools operated with
one hand. For precision operations, tools should weigh less than 1 pound (.5 kg). Tools heavier
than 1 kg or poorly balanced tools should be supported by counter-balancers. It is also
important that the center of gravity be aligned with the center of the gripping hand. In other
words, tools should feel "easy" to hold either in an upright position or in the position it will be
used (ie. pointing down).
Handles
Except for devices for exactness work (e.g., watch making, microsurgery, cutting), the handles
and grasps of hand instruments ought to be intended for a power hold. The conviction that
littler apparatuses ought to have littler handles while bigger devices have bigger ones is far
from being obviously true.
Handle shape
Apparatuses with "bowed" or calculated handles or devices with Pliers-grasps are
advantageous where the power is applied in a straight line indistinguishable way from the
rectified lower arm and wrist, particularly when the power must be connected on a level plane.
Devices with straight handles are for errands where the power is applied opposite to the
rectified lower arm and wrist, for example, when the power must be connected vertically.
Fig 03: Handles of Pliers
Knowing the errands and the format of the working environment where they will be utilized is
essential for choosing the correct devices for some random activity. The device requires wrist
flexion, expansion or deviation. As such, select devices that enable you to keep the wrist
straight or in an impartial position.
Diameter
Handles ought to be tube shaped or oval in cross area, with a distance across of between 25mm
and 40 mm. For accuracy work the prescribed width for handles is between 5 mm and 10 mm.
For a more noteworthy torque extensive screwdrivers ought to have a handle distance across
up to 45-55 mm. In any case, particularly for forceps the distance across is suggest 15mm-
20mm with elastic griper is the agreeable breadth.
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Length
A handle that is too short can cause superfluous pressure amidst the palm. It ought to reach out
over the whole broadness of the palm. Instrument handles longer than 100 mm (ideally 100-
110 mm) will lessen the negative impacts of any pressure applied. Adjusted handles will limit
palm pressure on the palm even more. Remember that the utilization of gloves requires longer
instrument handles.
Materials and texture of handles
The materials used to make pliers need to be of steel alloys with additives such
as vanadium or chromium, to improve strength and prevent corrosion. The metal handles of
pliers need to be fitted with grips of other materials to ensure better handling; grips are
usually insulated and additionally protect against electric shock. The jaws should wide in size,
from delicate needle-nose pliers to heavy jaws capable of exerting much pressure, and shape,
from basic flat jaws to various specialized and often asymmetrical jaw configurations for
specific manipulations. The surfaces are typically textured rather than smooth, to minimize
slipping. To guarantee a decent grasp on a handle, adequate grinding must exist between the
hand and the handle. This is especially essential where an impressive power must be connected
with a sweat-soaked hand. Hand apparatuses ought to be made of non-slip, non-conductive and
compressible materials. For example, textured rubber handles provide a good grip, reduce the
effort needed to use the tool effectively, and prevent the tool from slipping out of the hand.
Handles made of plastics or compound elastic is prescribed. Sharp edges and shapes can be
secured with padded tape to limit slashes.
Safe use of pliers
Do not substitute pliers for a wrench when turning nuts and bolts. Pliers cannot grip
these items properly and will slip.
Never use pliers as a hammer or hammer on the handles. Such abuse is likely to result
in cracks or breaks.
Cut hardened wire only with pliers designed for that purpose.
Always cut at right angles. Never rock from side to side or bend the wire back and forth
against the cutting edges.
Keep the distance between the two handles minimum 45 mm.
Use adjustable pliers that allow you to grip the workpiece firmly while maintaining a
comfortable handgrip (i.e., hand grasp is not too wide).
Use tools only if they are in good condition.
Make sure that the cutting edges are sharp. Dull and worn down cutting edges require
many times more force needed for cutting.
Make sure that the toothed jaws are clean and sharp. Greasy or worn down jaws can
result in compromised safety. Such tools also require increased force to hold the
workpiece which, in turn, increases the risk of muscular fatigue and repetitive strain
injuries.
Oil pliers and wire cutters regularly. A drop of oil on the hinge will make the tools
easier to use.
Pull on the pliers; do not push away from you when applying pressure. If the tools slips
unexpectedly, you may lose your balance or hit your hand against equipment or
something else hard that could result in an injury.
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Table 01: The table below summarizes some of the guidelines presented above
Guidelines – Summary
Description Guideline Reason
Tool shape Slightly contoured Easy grip
Direction of force is in-line with Bent handle Minimal wrist deviation
forearm and wrist (typically horizontal)
Direction of force is perpendicular to Straight handle Minimal wrist deviation
forearm and wrist (typically vertical)
Handle length > 100 mm (ideally 100 - Keep contact out of
110 mm) palm
Handle diameter (power grip) 15-20 mm Greater force and
stability
Material and texture of handles Non-slip non-conductive For comfort and
materials reduces effort required
to use tool
Tool weight (< 0.5 kg) Two handle 1 hand use
Conclusion
Regularly pliers have insulated grips to make certain higher handling and save you electric
conductivity. The materials used to make pliers consist specially of metallic alloys with
additives such as vanadium or chromium, to improve strength and save you corrosion. The
fundamental design of pliers has changed little for the reason that their origins, with the pair of
handles, the pivot (regularly formed via a rivet), and the pinnacle segment with the gripping
jaws or slicing edges forming the three factors. In difference to a couple of scissors or shears,
the pliers’ jaws always meet each other at one pivot angle. In a few lines of first-rate work
(together with jeweler or musical device repair), some specialized pliers characteristic a layer
of comparatively soft metal (consisting of brass) over the two plates of the top of the pliers to
lessen strain placed on some satisfactory equipment or substances. Making complete pliers out
of softer metals could be impractical, lowering the force required to bend or ruin them.
