This is my project of special studies of 3rd year.

1. DESIGN & CONSTRUCTION OF A SCISSOR
JACK
Course No: ME 3200
Supervised By Presented By
Dr. Md. Shahidul Islam Md Fahim Faisal
Professor Roll: 1405081
Department of Mechanical Engineering Section: B
Khulna University of Engineering & Technology

2. Introduction
► Jack is a device for lifting heavy objects, specially for raising the axle of a motor
vehicle off the ground to repair or inspect underside of the vehicle.
► Scissor jack is the most common form of different types of jacks.
► It is called a scissor jack as the structure consists of diagonal metal components
that expand and contract in the same way as a pair of scissors.
► In this project I have designed and constructed a scissor jack, and simplified it’s
construction.

3. Objectives
► To design a scissor jack.
► To construct a scissor jack.
► To simplify the construction.

4. CAD model of Scissor jack & it’s different
parts
Fig 1.1 : Arm of scissor
jack
Fig 1.2 : Bottom plate of
scissor jack
Fig 1.3 : Top plate of
scissor jack

5. CAD model of Scissor jack & it’s different
parts
Fig 1.4 : Power screw of
scissor jack
Fig 1.5 : Trunion
(with threaded hole)
Fig 1.6 : Trunion
(without threaded
hole)

6. CAD model of Scissor jack & it’s different
parts
Fig 1.7 : Assembly model of Scissor jack

7. DESIGN
Fig 1.8 : Force diagram of
scissor jack
Length of the arms used = 200 mm
The length from base to top center of holes (At Minimum
raising height of the jack), e =250 mm
Let’s assume, 200 kg weight will be raised.
After several calculations It was gotten that
Effort required to support the load is 2448.23 N.
Mean diameter of the power screw, d = 20 mm
So,
Torque required to rotate the screw ,τ = effort * d/2
= 2448.23 * 20/2
= 24482.30 N-mm
= 24.482 N-m

8. CONSTRUCTION
Contruction of arms of scissor jack :
Flat metal were cut by metal cutter as designed
dimensions. Corners were grinded by grinder. Cut two
drilled hole for each arm at their two ends by drill
machine.
Fig 1.9 : Arm of scissor jack
Contruction of power screw of scissor jack :
A circular rod was turned to the required dimensions in a
lathe machine.Then, a hand die was used to create thread.
After threading operation two end of the power screw
were grinded. Fig 1.10 : power screw of
scissor jack

9. CONSTRUCTION
Contruction of top plate of scissor jack :
A flat sheet metal was cut as designed dimension.Then
bended as shown in picture. Drilling operation was
operated by drill machine.
Contruction of bottom plate of scissor jack :
Three flat metal sheet were cut as designed dimensions.
Two metal sheet chamfered at two edges. Then two
metal sheet welded as picture shows. Four hole were
drilled by drilling machine as required.
Fig 1.11 : Bottom plate of
scissor jack

10. CONSTRUCTION
Contruction of trunions of scissor jack :
(a) Trunion with threaded hole:
Three metal sheet cut as dimensions.Then drilled as
shown.One hole is bored to fit a threaded nut as
shown.Then welded the joints should be welded.Finally
a threaded nut fitted in the bore by hudraulic press.
(b) Trunion without threaded hole:
Same as before, just at position of bore there is a drilled
hole to pass the power screw easily instead of a bore
with threaded nut.
Fig 1.12 : Trunion with threaded
hole
Fig 1.12 : Trunion without
threaded hole

11. Result & Performance
Result :
To raise 200 kg weight,
Torque required to rotate the power screw = 24.482 N-m
Performance :
According to design, to raise 200 kg-weight torque required 24.482 N-m. This
amount of torque is favourable for any adult human. So, this scissor jack is able to
raise any medium size of vehicle like cars from off the ground.

12. Conclusion
► In this project I have constructed a scissor jack ,it’s different parts.I also simplified
the constructing method.It’s construction process is simple comparatively to other
jacks.
► According to design it is proved that this scissor jack can lift a small and medium
size of vehicle. And it is easily possible for an adult man to meet the required
torque to rotate screw or raise vehicle.
► Finally , I have completed my all objectives.

13. THANK YOU ALL FOR YOUR KIND
ATTENTION