Manufacturing Processes Chapter 5

What is meant by the term graduated measuring device?

A graduated measuring device has markings (called graduations) on a linear or angular scale to measure an object's feature of interest (e.g., length).

Which of the following two geometric terms have the same meaning: (a) circularity, (b) concentricity, (c) cylindricity, and (d) roundness?

(a) and (d).

Surface texture includes which of the following characteristics of a surface (three correct answers): (a) deviations from the nominal surface, (b) feed marks of the tool that produced the surface, (c) hardness variations, (d) oil films, and (e) surface cracks?

(a), (b), and (e).

Surface texture is included within the scope of surface integrity: (a) true or (b) false?

(a).

Thermal energy is normally associated with which of the following changes in the altered layer (three best answers): (a) cracks, (b) hardness variations, (c) heat affected zone, (d) plastic deformation, (e) recrystallization, or (f) voids?

(b), (c), and (e).

Which of the following are likely to be GO/NO-GO gages (three correct answers): (a) gage blocks, (b) limit gage, (c) master gage, (d) plug gage, and (e) snap gage?

(b), (d), and (e).

In a GO/NO-GO gage, which one of the following best describes the function of the GO gage: (a) checks limit of maximum tolerance, (b) checks maximum material condition, (c) checks maximum size, (d) checks minimum material condition, or (e) checks minimum size?

(b).

Which one of the following manufacturing processes will likely result in the best surface finish: (a) arc welding, (b) grinding, (c) machining, (d) sand casting, or (e) sawing?

(b).

An outside micrometer would be appropriate for measuring which of the following (two correct answers): (a) hole depth, (b) hole diameter, (c) part length, (d) shaft diameter, and (e) surface roughness?

(c) and (d).

A surface plate is most typically made of which one of the following materials: (a) aluminum oxide ceramic, (b) cast iron, (c) granite, (d) hard polymers, or (e) stainless steel?

(c).

A tolerance is which one of the following: (a) clearance between a shaft and a mating hole, (b) measurement error, (c) total permissible variation from a specified dimension, or (d) variation in manufacturing?

(c).

Which one of the following manufacturing processes will likely result in the worst surface finish: (a) cold rolling, (b) grinding, (c) machining, (d) sand casting, or (e) sawing?

(d). Also, sawing (e) will yield a poor finish. Either answer is acceptable.

What is the difference between a bilateral tolerance and a unilateral tolerance?

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.

What is a tolerance?

A tolerance is defined as the total amount by which a specified dimension is permitted to vary.

What is accuracy in measurement?

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.

What are the common methods for assessing surface roughness?

Common methods for assessing surface roughness are (1) comparison of the specimen surface with standard test blocks having known surface roughness values and (2) stylus-type electronic instruments which measure average roughness.

What causes the various types of changes that occur in the altered layer just beneath the surface?

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.

What is precision in measurement?

Precision in measurement is the degree to which random errors are minimized.

Name some manufacturing processes that produce very poor surface finishes.

Processes that produce poor surfaces include sand casting, hot rolling, sawing, and thermal cutting (e.g., flame cutting).

Name some manufacturing processes that produce very good or excellent surface finishes.

Processes that produced very good and excellent surfaces include honing, lapping, polishing, and superfinishing.

Within the scope of surface texture, how is roughness distinguished from waviness?

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.

Surface roughness is a measurable aspect of surface texture; what does surface roughness mean?

Surface roughness is defined as the average value of the vertical deviations from the nominal surface over a specified surface length.

Indicate some of the limitations of using surface roughness as a measure of surface texture.

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.

Define surface texture.

Surface texture is the random and repetitive deviations from the nominal surface, including roughness, waviness, lay, and flaws.

How is surface texture distinguished from surface integrity?

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.

Identify some of the changes and injuries that can occur at or immediately below the surface of a metal.

The changes and injuries include: cracks, craters, variations in hardness near the surface, metallurgical changes resulting from heat, residual stresses, intergranular attack, etc. (see Table 5.1).

Based on the video about vernier calipers, are the markings on the vernier plate (moveable scale) the same spacing, slightly closer, or slightly further apart compared to the stationary bar?

The markings are slightly closer. The 50 markings on the vernier plate fit in place of 49 markings on the stationary bar.

Define nominal surface.

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.

Based on the video about vernier calipers, explain how to read the scale on a vernier caliper.

The object is inserted between the jaws. The distance between the zero on the stationary bar and the zero on the vernier plate (moveable scale) is added to the number that corresponds to the line that exactly lines up on the vernier plate. Only one mark on the veriner plate will line up with a mark on the stationary bar.

What are some of the reasons why surfaces are important?

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.

Based on the video about micrometers, explain the primary factor that makes an English micrometer different from a metric micrometer.

The thread pitch determines the linear motion of the micrometer for each rotation of the barrel. A metric micrometer will use a different pitch than an English micrometer.