Solutions for Introduction to Manufacturing Processes (published by Wiley)  MPGroover 2011
06-14, 06-14-2010
4 DIMENSIONS, TOLERANCES AND SURFACES
Review Questions
4.1
What is a tolerance?
Answer. A tolerance is defined as the total amount by which a specified dimension is permitted to
vary.
4.2
What is the difference between a bilateral tolerance and a unilateral tolerance?
Answer. A bilateral tolerance allows variation in both positive and negative directions from the
nominal dimension, whereas a unilateral tolerance allows the variation from the nominal dimension
to be either positive or negative, but not both.
4.3
What is accuracy in measurement?
Answer. Accuracy is the degree to which the measured value agrees with the true value of the
quantity of interest. It is a measurement procedure that is absent of systematic errors.
4.4
What is precision in measurement?
Answer. Precision in measurement is the degree to which random errors are minimized.
4.5
What are some of the reasons why surfaces are important?
Answer. The reasons why surfaces are important include: aesthetics, safety, friction and wear, effect
of surface on mechanical and physical properties, mating of components in assembly, and electrical
contacts.
4.6
Define nominal surface.
Answer. The nominal surface is the ideal part surface represented on an engineering drawing. It is
assumed perfectly smooth; perfectly flat if referring to a planar surface; perfectly round if referring to
a round surface, etc.
4.7
Define surface texture.
Answer. Surface texture is the random and repetitive deviations from the nominal surface, including
roughness, waviness, lay, and flaws.
4.8
How is surface texture distinguished from surface integrity?
Answer. Surface texture refers only to the surface geometry; surface integrity includes not only
surface but the subsurface layer beneath the surface and the changes in it.
4.9
Within the scope of surface texture, how is roughness distinguished from waviness?
Answer. Roughness consists of the finely-spaced deviations from the nominal surface, while
waviness refers to the deviations of larger spacing. Roughness deviations lie within waviness
deviations.
4.10 Surface roughness is a measurable aspect of surface texture; what does surface roughness mean?
Answer. Surface roughness is defined as the average value of the vertical deviations from the
nominal surface over a specified surface length.
4.11 Indicate some of the limitations of using surface roughness as a measure of surface texture.
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Solutions for Introduction to Manufacturing Processes (published by Wiley)  MPGroover 2011
06-14, 06-14-2010
Answer. Surface roughness provides only a single measure of surface texture. Among its limitations
are: (1) it varies depending on direction; (2) it does not indicate lay; (3) its value depends on the
roughness width cutoff used to measure the average.
4.12 What causes the various types of changes that occur in the altered layer just beneath the surface?
Answer. Energy input to the surface resulting from the manufacturing process used to generate the
surface. The energy forms can be any of several types, including mechanical, thermal, chemical, and
electrical.
4.13 Name some manufacturing processes that produce very poor surface finishes.
Answer. Processes that produce poor surfaces include sand casting, hot rolling, sawing, and thermal
cutting (e.g., flame cutting).
4.14 Name some manufacturing processes that produce very good or excellent surface finishes.
Answer. Processes that produced very good and excellent surfaces include honing, lapping,
polishing, and superfinishing.
Excerpts from this work may be reproduced by instructors for distribution on a not-for-profit basis for testing or instructional purposes only to
students enrolled in courses for which the textbook has been adopted. Any other reproduction or translation of this work beyond that permitted
by Sections 107 or 108 of the 1976 United States Copyright Act without the permission of the copyright owner is unlawful.
4-2