Page 609 - 04. Subyek Engineering Materials - Manufacturing, Engineering and Technology SI 6th Edition - Serope Kalpakjian, Stephen Schmid (2009)

590 Chapter 21 Fundamentals of Machining

rake angles that give the same cutting ratio. R = 1 mm and a desired roughness of 1 um. How would
|]2|.50. With appropriate diagrams, show how the use of you adjust this feed to allow for nose wear of the tool during
a cutting fluid can change the magnitude of the thrust force, extended cuts? Explain your reasoning.
F,, in Fig. 21.11. ll2l.54. With a carbide tool, the temperature in a cutting
u2I.5I. For a turning operation using a ceramic cutting operation is measured as 650K when the speed is 90 m/min
and the feed is 0.05 mm/rev. What is the approximate tem-
tool, if the speed is increased by 50%, by what factor must
the feed rate be modified to obtain a constant tool life? Use perature if the speed is doubled? What speed is required to
n = 0.5 and y = 0.6. lower the maximum cutting temperature to 480K?
2l.55. Assume that you are an instructor covering the top-
|12 l.52. In Example 21.3, if the cutting speed V is doubled,
will the answer be different? Explain. ics described in this chapter and you are giving a quiz on the
numerical aspects to test the understanding of the students.
21.53. Using Eq. (21.24), select an appropriate feed for
Prepare two quantitative problems and supply the answers.

SYNTHESIS, DESIGN, AND PROIECTS

|12 l.56. As we have seen, chips carry away the majority of the with a sharp knife. Using butter at different temperatures, in-
heat generated during machining. If chips did not have this ca- cluding frozen butter, conduct such an experiment. Keep the
pacity, what suggestions would you make in order to be able to depth of cut constant and hold the knife at different angles
carry out machining processes without excessive heat? Explain. (to simulate the tool rake angle), including oblique scraping.
2l.57. Tool life is increased greatly when an effective means Describe your observations regarding the type of chips
of cooling and lubrication is implemented. Design methods of produced. Also, comment on the force that your hand feels
delivering this fluid to the cutting zone and discuss the advan- while scraping and whether you observe any chatter when the
butter is very cold.
tages and limitations of your design.
2l.58. Design an experimental setup whereby orthogonal 2I.62. Experiments have shown that it is possible to pro-
duce thin, wide chips, such as 0.08 mm thick and 10 mm
cutting can be simulated in a turning operation on a lathe.
wide, which would be similar to the dimensions of a rolled
2l.59. Describe your thoughts on whether chips produced
sheet. Materials have been aluminum, magnesium, and stain-
during machining can be used to make useful products. Give
less steel. A typical setup would be similar to orthogonal cut-
some examples of possible products, and comment on their ting, by machining the periphery of a solid round bar with a
characteristics and differences if the same products were straight tool moving radially inward. Describe your thoughts
made by other manufacturing processes. Which types of chips
regarding producing thin metal sheets by this method, taking
would be desirable for this purpose?
into account the metal’s surface characteristics and proper-
2l.60. Recall that cutting tools can be designed so that the t16S.
tool-chip contact length is reduced by recessing the rake face 2|.63. Describe your thoughts regarding the recycling of
of the tool some distance away from its tip. Explain the pos-
chips produced during machining in a plant. Consider chips
sible advantages of such a tool.
produced by dry cutting versus those produced by machining
l]2|.6|. Recall that the chip-formation mechanism also with a cutting fluid.
can be observed by scraping the surface of a stick of butter