MCQ’s On Threaded Joints in Machine Design
Q. Threaded joints are non-separable joints.
A. True
B. False
Answer: B
Explanation: Threaded joints are separable joints of machine parts that are held together by means of a threaded fastening such as nut and bolt.
Q. Which type of joints is better when the product is subjected to large vibrations: welded or threaded?
A. Welded
B. Threaded
C. Both have same results
D. Depends on the magnitude of the vibrational force
Answer: A
Explanation: Threaded joints loosen when subjected to vibrations.
Q. If a fastener is threaded into a tapped hole, then the fastener is likely to be called as
A. Screw
B. Bolt
C. Washer
D. Screw or bolt
Answer: A
Explanation: Bolt is threaded into a nut while screw is threaded into a tapped hole.
Q. In nut and bolt fastener, nut is generally held stationary while bolt is rotated.
A. True
B. False
Answer: B
Explanation: Bolt is always held stationary while nut is rotated.
Q. Which of the following is not a function of washer?
A. Distributes load over a large area of clamped parts
B. Provides bearing surface over large clearance bolts
C. Prevents marring of the bolt head and nut surface
D. Helps in locking of the fastener
.
Answer: D
Explanation: Washer doesn’t help in locking of fasteners.
Q. Shank is the portion of bolt between the head and the thread.
A. True
B. False
Answer: A
Explanation: Shank is the portion between head and the thread of the bolt.
Q. If there is no place to accommodate the nut, then one would choose the
A. Through Bolts
B. Tap Bolts
C. Studs
D. None of the mentioned
.
Answer: B
Explanation: Tap bolts are directly threaded into the clamped parts and does not require any nut.
Q. Which of the following are good for parts that are seldom dismantled.
A. Through Bolts
B. Tap Bolts
C. Studs
D. Cannot be stated
Answer: B
Explanation: Tap bolts, if removed frequently will leave the threads in the part worn out and hence are used where dismantling is rare.
Q. Which of the following requires more space for the rotation of spanner?
A. Square Head
B. Hexagonal Head
C. Both require equal space of rotation
D. Cannot be stated
Answer: A
Explanation: Angle of rotation for hexagonal head is one sixth of a revolution to enable the next pair of flats to be engaged while it is one fourth of a revolution in case of square head.
Q. Fillister, button, flat and hexagonal heads are all tightened externally.
A. True
B. False
.
Answer: B
Explanation: All of these are internal drive screws having a slot for the screw driver of different shape on the head.
Q. Set screws are subjected to tensile forces only.
A. Yes
B. No, they are subjected to compressive forces only
C. Both compressive and tensile
D. Can’t be determined
Answer: B
Explanation: Set screws are subjected to compressive forces only.
Q. If the lateral force acting on the set screw is large and tends to displace one part with respect to other than which point is recommended?
A. Dog Point
B. Cone Point
C. Window Point
D. Cut Point
.
Answer: A
Explanation: Dog point is used when the lateral force is large provided the part has sufficient thickness to accommodate a cylindrical hole for dog point.
Q. Find the torque required to raise the load of 15kN and mean diameter of triple threaded screw being 46mm. Also given pitch=8mm and coefficient of friction is 0.15.
A. 11831.06N-mm
B. 11813.06N-mm
C. 12811.06N-mm
D. None of the listed
.
Answer: A
Explanation: tanἀ=l/πd or ἀ=9.429’ as l=3p. tan Ǿ=0.15 or Ǿ=8.531’. M=W x d x tan (Ǿ+ἀ)/2.
Q. What is the collar friction torque if outer and inner diameters are 100mm and 65mm respectively. Coefficient of friction is 0.15 and the load acting is of 15kN. Consider uniform wear theory.
A. 89886.6N-mm
B. 38796.5N-mm
C. 92812.5N-mm
D. 87645.5N-mm
Answer: C
Explanation:M=0.15 x W(D+D./4.
Q. For a double threaded screw, what will be the tangent of helix angle if nominal diameter and pitch are 100mm and 12mm respectively?
A. 0.045
B. 0.081
C. 0.094
D. 0.023
.
Answer: B
Explanation: tan ἀ= l/πd where l=2p, d=D-0.5p.
Q. If for a trapezoidal thread, angle of thread is 15’ then what will be the replacement of the coefficient of friction which is 0.15.
A. 0.1553
B. 0.1335
C. 0.1667
D. 0.1776
Answer: A
Explanation: f=0.15 x sec 15’.
Q. What will be efficiency of the screw in case of raising the load when coefficient of friction is 0.1553 and tangent of helix angle is 0.0813?
A. 34%
B. 45%
C. 54%
D. 43%
.
Answer: A
Explanation: Efficiency= tanἀ(1-0.1553 x tan ἀ)/(0.1553+tanἀ).
Q.A machine vice whose length of the handle is 150mm and the coefficient of friction for thread and collar are 0.15 and 0.17 respectively has a force applied at handle of 125N. Also the outer and inner diameters of collar are 55mm and 45mm respectively. Find the screw torque in terms of clamping force W if nominal diameter=22mm and pitch=5mm.
A. 3.567W N-mm
B. 2.286W N-mm
C. 3.564W N-mm
D. None of the mentioned
.
Answer: B
Explanation: M₁=Wd x tan(Ǿ+ἀ)/2 or M₁=W x (22-0.5×2.5)x tan(4.66’+8.531’)/2 as tan(ἀ)=l/πd and tanǾ=0.15.
Q.A machine vice whose length of the handle is 150mm and the coefficient of friction for thread and collar are 0.15 and 0.17 respectively has a force applied at handle of 125N. Also the outer and inner diameters of collar are 55mm and 45mm respectively. Find the collar torque in terms of clamping force W assuming uniform wear theory if nominal diameter=22mm and pitch=5mm.
A. 4.5W
B. 5.4W
C. 4.25W
D. 3.37W
.
Answer: C
Explanation: M₂=0.17 x W x (55+45)/4 or M₂=4.25W N-mm.
Q.A machine vice whose length of the handle is 150mm and the coefficient of friction for thread and collar are 0.15 and 0.17 respectively has a force applied at handle of 125N. Also the outer and inner diameters of collar are 55mm and 45mm respectively. Find the clamping force W if nominal diameter=22mm and pitch=5mm.
A. 4539.45N
B. 2868.73N
C. 3657.56N
D. 2134.34N
.
Answer: B
Explanation: Net torque=M₁+M₂ or 125 x 150=2.286W + 4.25W or W=2868.73N.
Q.A machine vice whose length of the handle is 150mm and the coefficient of friction for thread and collar are 0.15 and 0.17 respectively has a force applied at handle of 125N. Also the outer and inner diameters of collar are 55mm and 45mm respectively. Find the overall efficiency if nominal diameter=22mm and pitch=5mm.
A. 18.12%
B. 12.18%
C. 21.23%
D. 23.21%
.
Answer: B
Explanation: Efficiency= W l/2π(M₁+M₂) where
M₁=2.286W [M₁=Wd x tan (Ǿ+ἀ)/2 or M₁=W x (22-0.5×2.5) x tan (4.66’+8.531’)/2 as tan(ἀ)=l/πd and tan Ǿ=0.15].
M₂=4.25W [M₂=0.17 x W x (55+45)/4 or M₂=4.25W N-mm],
l=5mm,
W=2868.73N [Net torque=M₁+M₂ or 125 x 150=2.286W + 4.25W or W=2868.73N].
Q. Find the bending stress to which a screw of nominal diameter 22mm is subjected when the clamp exerts a force of 5kN acts on it. The screw is double threaded and pitch of screw is 5mm.Given: Coefficient of friction is 0.15.It is assumed operator exerts a force of 250N at the handle of length 275mm.
A. 123.45N/mm²
B. 132.54N/mm²
C. 142.54N/mm²
D. 124.45N/mm²
.
Answer: C
Explanation: Bending stress=32M/πdᵌ where M=250 x 275N-mm,d=22-2 x 0.5 x 5mm.
Q. Find the torsional shear stress to which a screw of nominal diameter 22mm is subjected when the clamp exerts a force of 5kN on it. The screw is double threaded and pitch of screw is 5mm.Given: Coefficient of friction is 0.15.
A. 25.45N/mm²
B. 21.29N/mm²
C. 31.21N/mm²
D. 35.65N/mm²
.
Answer: B
Explanation:=16M/πd₂ᵌ where M=Wd₁ tan (Ǿ+ἀ)/2 where d₁=22-0.5 x 5,W=5000N,
tanἀ=2 x 5/[πx19.5] and d₂=19.5-0.5 x 5.
Q. If bending stress in a screw is of magnitude 95N/mm² and torsional shear stress of magnitude 15N/mm², then what is the principal shear stress?
A. 48.7N/mm²
B. 54.3 N/mm²
C. 51.4 N/mm²
D. 49.8 N/mm²
.
Answer: D
Explanation:τ(max)=√(95/2)²+15².
Q. The nominal diameter of the screw is 22mm and the allowable bearing pressure for the nut is 15N//mm². Find the length of the nut if pitch of the screw is
A. 15mm
B. 20mm
C. 25mm
D. 30mm
.
Answer: A
Explanation:z=4W/π S(d₁²-d₂²) where S=15N/mm²,d₁=22mm and d₂=17mm. Hencez=2.2 or z=Length of nut=zp or l=3 x 5= 15mm.
Q.A but joint can be defined as a joint between two components lying approximately in a different plane.
A. True
B. False
.
Answer: B
Explanation: Butt joint is defined a joint between two plates lying in the same plane.
Q.A fillet weld is an approximately triangular cross section joining two surfaces lying parallels to each other.
A. True
B. False
.
Answer: B
Explanation: Two surfaces lie perpendicular to each other.
Q. How many types of jacks are there which can be used in a screw jack?
A. 2
B. 3
C. 4
D. 5
.
Answer: A
Explanation: Hydraulic jack and mechanical jack.
Q. Which of the following does not form the important part of the screw jack?
A. Frame
B. Nut
C. Cup
D. Coupling
.
Answer: D
Explanation: There is no specific requirement of coupling in the screw jack.
Q. The transverse shear stress at the root of the threads in the nut can be given by?(symbols have their usual meaning, z=number of threads in nut)
A. 4W/πdz²
B. W/πdtz
C. 4W/πtd²
D. None of the mentioned
.
Answer: B
Explanation: At root of threads, the area parallel to direction of force is considered which is equal to circumference x thickness x no. of threads.
Q. What type of friction in cup design is recommended for the set screw?
A. Sliding
B. Rolling
C. Static
D. None of the mentioned
.
Answer: B
Explanation: Sliding friction, the total force require to raise the load is quite large as compared to that required in rolling friction. Hence length of handle in some cases becomes extremely large and thus it is impractical to use cups with sliding friction.
Q.A differential screw is defined as a mechanical device consisting of two screws connected in parallel.
A. True
B. False
.
Answer: B
Explanation: The two screws are connected in series.
Q.In a differential screw, two screws are connected in series such that the resultant motion is the summation of the motion of the two screws.
A. True
B. False
.
Answer: B
Explanation: The resultant motion is the difference of the individual motion of two screws.
Q.A compound screw consist of two screws in parallel such that the resultant motion is the summation of the individual motion of screws.
A. True
B. False
.
Answer: B
Explanation:The two screws are connected in series with the resultant motion being the sum of individual motion.
Q. What is the output from differential screws when pitch of the two screws is 12mm and 8mm? Also the nut is rotated by applying a force of 120N at a radius of 300mm and the two screws remain stationary. The torque of raising and lowering for the two screws is 5k N-mm and 2.5k N-mm where k is the effective axial weight on the screw.
A. 13200 N-mm
B. 15200 N-mm
C. 19200 N-mm
D. 17200 N-mm
.
Answer: C
Explanation:120 x 300=5k+2.5k or k=4800N. Output=k x (12-8) or output=19200N-mm.
Q. What is the efficiency of differential screws when pitch of the two screws is 12mm and 8mm? The nut is rotated by applying a force of 120N at a radius of 300mm and the two screws remain stationary. The torque of raising and lowering for the two screws is 5k N-mm and 2.5k N-mm where k is the effective axial weight on the screw.
A. 6.48%
B. 8.48%
C. 23.1%
D. 42.8%
.
Answer: B
Explanation:120 x 300=5k+2.5k or k=4800N. Output=k x (12-8) or output=19200N-mm. Efficiency=output/2πx120x300.
Q. Efficiency of conventional power screw is greater than the efficiency of recirculating ball screw.
A. True
B. False
.
Answer: B
Explanation: In recirculating ball screw, sliding friction is replaced by rolling friction and efficiency increases from 40% to 90%.
Q. In which case is the wear more?
A. Conventional power screw
B. Recirculating power screw
C. Equal in both the cases
D. Cannot be determined
.
Answer: A
Explanation: In recirculating ball screw, there is a lubricant film between the contacting surfaces and hence lesser wear.
Q. Resilience is defined as the property of material to absorb energy when deformed _________ and to release this energy when unloaded.
A. Elastically
B. Plastically
C. Up to fracture point
D. None of the listed
.
Answer: A
Explanation:It is the definition of resilience.
Q.The shock absorbing capacity of bolt can be increased by making the shank diameter ________ the root diameter.
A. Lesser than
B. Equal to
C. Greater than
D. No effect
.
Answer: B
Explanation:If shank diameter is equal to the thread diameter than, the shank is subjected to higher stress and thus absorbs a great portion of strain energy and relieves the thread portion of high stress.
Q.The shock absorbing capacity of bolts can be increased by
A. Increasing the shank diameter
B. Decreasing the length of shank portion of bolt
C. Increase the shank diameter and decreasing the length of shank
D. None of the listed
.
Answer: D
Explanation:Shock absorbing capacity can be increased by decreasing the shank diameter or increasing the length of shank.
Q.If the length of the shank is doubled, then strain energy absorbed by shank
A. Doubles
B. Remains same
C. Increases 4 time
D. Become half
.
Answer: A
Explanation: Strain energy absorbed by shank is linearly proportional to its length.
Q. of the following help in accomplishing the locking?
A. Creating supplementary friction
B. Using special locking devices like split pins
C. By plastic deformation
D. All of the listed
.
Answer: D
Explanation: All the methods can be employed to lock the screw.
Q. Crests and roots of the threads may lead to leakage in fluid tight threads if flattened or rounded to a circular arc.
A. True
B. False
.
Answer: B
Explanation: As there is engagement in the threads, chances of leakage are reduced.
Q.The static load carrying capacity of fine threads is greater than that of coarse threads.
A. True
B. False
.
Answer: B
Explanation: Coarse threads have a higher load carrying capacity.
Q. Coarse threads have helix angle _____ fine threads.
A. Equal to
B. Greater than
C. Lesser than
D. There is no relation
.
Answer: C
Explanation: Finer threads have lower helix angle.
Q. Which threads have greater resistance to unscrewing?
A. Coarse
B. Fine
C. They have equal resistance
D. Cannot be determined
.
Answer: B
Explanation: Fine threads have greater resistance to unscrewing as a result of lower helix angle.
Q. Which type of threads is recommended for fluctuating loads?
A. Fine threads
B. Coarse Threads
C. Either of fine or coarse
D. None of the listed
.
Answer: A
Explanation: Fine threads have lesser helix angle and hence greater resistance for unscrewing and thus are recommended for fluctuating loads.
Q. Which of the following statements are true about eccentrically loaded circular base?
A. All bolts are symmetrically spaced with equal angle on either side of vertical
B. Bolts are not preloaded
C. Bearing is rigid
D. Dowel pins are used to relieve stresses
.
Answer: A
Explanation: Bolts are symmetrically placed only in a special case.
Q. Certain types of radial bearings can also take thrust load.
A. True
B. False
.
Answer: A
Explanation: Sometimes radial bearings can take thrust load and vice versa.
Q. Balls and the races of the deep groove ball may roll freely without any sliding.
A. True
B. False
.
Answer: A
Explanation: There is a point contact between the balls and the races.
Q.A flange of radius 200mm is fastened to the machine screw by means of four cap screws of pitch circle radius 150mm. The external force P is 20kN which is loaded at 160mm from the machine screw. There are two dowel pins to take shear load. Determine the maximum effective tensile force acting on the bolt. The four bolts are equally spaced radially.
A. 4777.6N
B. 5777.6N
C. 6777.6N
D. 7777.7N
.
Answer: A
Explanation: Maximum force F=2Pl[a+bCos(90/2)] / 4(2a²+b²).
Q.A flange of radius 200mm is fastened to the machine screw by means of four cap screws of pitch circle radius 150mm. The external force P is 20kN which is loaded at 160mm from the machine screw. There are two dowel pins to take shear load. Determine the core diameter of cap screw if permissible tensile stress in cap screw is 40N/mm².
A. None of the listed
B. 11.21mm
C. 12.33mm
D. 14.12mm
.
Answer: C
Explanation: Maximum tensile force=4777.6N or πd² x σ/4=4777.6N.
