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This set of Machine Drawing Multiple Choice Questions & Answers (MCQs) focuses on “Thread Designation”.

1. A metric thread is designated by _________
a) its profile of the groove
b) letter M
c) its hand of the helix

Explanation: A metric thread is designated by letter M. It is then followed by major diameter in mm followed by the pitch with an ‘x’ sign in between the diameter and pitch. Coarse pitch is considered if the pitch is not defined.

2. What do you mean by M10?
a) Metric thread with a major diameter of 10.00mm and fine pitch
b) Metric thread with a major diameter of 10.00mm and coarse pitch
c) Metric thread with a major diameter of 10.00cm and fine pitch
d) Metric thread with a minor diameter of 10.00mm and coarse pitch

Explanation: M denotes metric thread. 10 followed by M denotes a major diameter of thread in mm. here, pitch is not defined. So, it is taken as a coarse pitch thread.

3. Which thread is denoted by SQ 40*10?
a) Square thread with 40mm major diameter and 10mm pitch
b) Square thread with 10mm major diameter and 40mm pitch
c) Metric thread with 40mm major diameter and 10mm pitch
d) Square thread with 40mm minor diameter and 10mm pitch

Explanation: If a thread is not a metric thread, type of thread is given in abbreviated form. Square thread is abbreviated as SQ. 40*10 denotes 40mm major diameter and 10mm pitch.
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5. If not specified, a left hand, single start thread of usual tolerance and grade is presumed.
a) True
b) False

Explanation: Threads are specified by type of thread profile, major diameter, tolerance, hand of helix and start of threads. If not specified, a right hand, single start thread of usual tolerance and grade is presumed.

6. If a thread is specified as ‘M 16*1.5 8 g LH DOUBLE’, g stands for ____________
a) type of pitch – coarse
c) tolerance
d) hand of the helix

Explanation: In a given thread specification g is used for tolerance. It is in lower case, representing external threads. If it is in upper case (G), it will be representing internal threads.

a) M 45*2-7-H-RH-DOUBLE
b) M 45*2-7-h-RH-DOUBLE
c) M 45*2-7-H-LH-DOUBLE
d) M 45*7-2-H-RH-DOUBLE

Explanation: None.

Sanfoundry Global Education & Learning Series – Machine Drawing.