This set of Engineering Metrology Multiple Choice Questions & Answers (MCQs) focuses on “Screw Threads Terminology”.

1. What is the name of screw thread which is formed on a cone?

Explanation: A screw thread is formed by forming a continuous helical groove on the external or internal surface of cylinder. The screw thread formed on frustum of a cone or a cone is called as tapered screw thread.

2. What type of thread is formed on female screw gauge?
c) Both internal and external

Explanation: An internal thread is that which formed on the inside of a workpiece e.g. on female screw gauge or a nut. An external thread is that which formed on the outside of a workpiece e.g on bolts or studs.

3. Which of the following option is true for truncation?
a) Thread can be tranculated at crest only
b) Thread can be tranculatd at root only
c) Thread can be tranculated at crest and root both
d) Thread can’t be tranculated at crest and root both

Explanation: A thread is truncated sometimes at the crest or at the root or at both root and crest and root. The radial distance from the crest to the nearest apex of the fundamental triangle is truncation at the crest is and at the root it is the radial distance from the root to the nearest apex.

4. What is dedendum for external threads?
a) Radial distance between pitch and minor cylinder
b) Radial distance between major and pitch cylinder
c) Radial distance between major and minor cylinder
d) Axial distance between major and pitch cylinder

Explanation: Addendum for an external thread is defined as the radial distance between the major cylinder and pitch cylinder and for internal addendum is the radial distance between the minor cylinder and pitch cylinder. Dedendum for external thread is the radial distance between the pitch cylinder and minor cylinder and this is the radial distance between the major and pitch cylinders for internal thread.

5. Which of the following is not a name of the major diameter of an external thread?
a) Outside diameter
b) Crest diameter
c) Full diameter
d) Cone diameter

Explanation: For a straight thread, Major diameter is the diameter of the major cylinder. It is also known to as the outside diameter or full diameter for external threads. Sometimes it is also called crest diameter.
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6. Which of the following is not true about the axial thickness of screw thread?
a) Measured in direction perpendicular to the axis of thread
b) Measured on pitch cylinder
c) Distance between opposite faces of same thread
d) Measured at the same thread

Explanation: In a screw thread axial thickness is the distance between the opposite faces of the same thread. It is measured on the pitch cylinder and in a direction parallel to the thread axis.

7. What is the alternative name of functional diameter?
a) Cone diameter
b) Virtual diameter
c) Root diameter
d) Inside diameter

Explanation: Functional diameter is also known as virtual diameter. For an internal or external thread, this is the pitch diameter of the enveloping thread, lead and flank angles having the full depth of engagement but not at roots and crests.

a) Pitch in inches
b) Axial distance moved by threaded part
c) Reciprocal of pitch in inches

Explanation: Thread per inch is the reciprocal of the pitch(inches). The angle made by the thread helix at the pitch line with plane perpendicular to the axis is known as lead angle. Lead angle is measured in an axial plane.

9. Which of the following is not true about effective diameter?
a) Also known as pitch diameter
b) It decides quality of fit between nut and screw
c) This is the diameter of minor cylinder
d) It is a very important dimension for screw threads

Explanation: In case of straight thread, effective diameter is the diameter of the pitch cylinder and is also called as pitch diameter. Effective diameter is the most important dimension at it decides the quality of the fit between the nut and the screw.

10. Which of the following is true for the multiple start screw threads?
a) It is produced by a single helical groove
b) Grooves should be different in spacing
c) It gives a quick transverse
d) It is formed in a transverse section on a cylinder

Explanation: Multiple start screw threads is produced by forming two or more than two helical grooves, equally spaced and similarly formed in an axial section on a cylinder. This gives a ‘quick traverse’ without sacrificing core strength.

11. Which of the following statement is true for screw threads?
Statement 1: Flank angle of symmetrical thread is known as thread’s half-angle.
Statement 2: It is measured parallel to the axis of a thread.
a) T, F
b) F, F
c) T, T
d) F, T

Explanation: In a screw thread the angles between individual flanks and perpendicular to the thread axis which passes through the vertex of the fundamental triangle are called flank angles. The flank angle of a symmetrical thread is called as the half-angle of a thread.

12. Flanks of the threads connect the crest with the roots.
a) True
b) False

Explanation: Flanks of thread are straight edges which connect the crest and the root. Angle of thread is the angle between the flanks or slope of the thread measured in an axial plane and also known as the included angle.

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