This set of Machine Drawing Multiple Choice Questions & Answers (MCQs) focuses on “Thread Profile”.
MCQs based on Thread Profile:
1. If a screw thread advances in the nut when turned in a clockwise direction, it is called _________
a) left hand helix
b) right hand helix
c) clockwise helix
d) anticlockwise helix
Explanation: Right hand helix has the thread that advances in the nut when turned in a clockwise direction. When thread advances in the nut when turned in an anticlockwise direction then it is termed as left hand helix thread.
2. Threads are classified into V thread, Acme thread, Knuckle thread, etc. on the basis of _________
a) start of threads
b) hand of helix
c) profile of the groove
Explanation: On the basis of the profile of the groove, threads are classified as V thread, Acme thread, Knuckle thread, Buttress thread, Square thread, etc. On the basis of start of threads, threads are classified as single start, double start, triple start, etc.
3. Pitch of the profile depends on the ______
a) nominal diameter
b) internal diameter
c) external diameter
d) mean diameter
Explanation: Threads are specified according to their pitch of profile. Pitch of the profile depends on the nominal diameter of the thread. The proportions of the profile are calculated in terms of the pitch.
4. Metric threads are not termed as ___________
a) BSW thread
b) V thread
c) American thread
d) Unified thread
Explanation: A practical modification of V thread is called a metric thread. It is also called an American thread or Unified thread. All these have the included angle of 600. But in BSW thread included angle is 550 and hence it is different.
5. Depth of thread is ______ times of pitch in case of British Standard Whitworth Thread.
Explanation: BSW threads are similar to the V threads, but the included angle is 55o. The depth of thread in case of BSW thread is 0.64 times of pitch of the thread. Radii at root and crest are 0.14 times that of pitch.
6. Vice used for carpentry work has ______ thread.
Explanation: Buttress threads are used where power is to be transmitted in a single direction only. Hence it is used in applications like vice used for carpentry work. It has efficiency as good as square thread and strength as much as V thread.
7. Which of the following option do not specify a knuckle thread?
a) Semi-circular profile of radius 1/4th of pitch
b) Suitably formed by molding or rolling
c) Used in sheet metal covers for jars
d) Transmits power in one direction only
Explanation: Knuckle thread has a semi-circular profile of radius 1/4th of the pitch. Knuckle threads are suitably formed by molding as well as rolling and can be used in sheet metal covers for jars. But thread which can transmit power in one direction only is Buttress thread.
8. Coarse pitches are used for ____________
a) rough application
b) general application
c) precision application
d) special application
Explanation: Pitch for the same diameter thread varies depending upon the application. Coarse pitch is used for rough application, medium pitch for general application and fine pitch is used for precision work.
9. Square threads are used for ________
a) power transmission
b) clamping devices
c) easy operation of engagement and disengagement
d) fastening purpose
Explanation: Square thread is the simple and strong type of thread profile. It is used for power transmission. Its width and depth are equal to the half of the pitch.
10. __________ is the slight improvement over square thread.
a) Buttress thread
b) Knuckle thread
c) Acme thread
d) BSW thread
Explanation: An acme thread is a slight improvement over square thread. Sides of the acme thread are inclined at 14.50. Square thread is difficult to cut because a parallel surface of both flanks and hence acme thread are used instead at some places.