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Unformatted text preview: 720 Chapter 23 Machining Processes Used t ' ESTIONS ! '1, Describe the types of machining operations that
can’be performed on a lathe. 23.2 Explain the functions of different angles on a
single-point cutting tool. 23.3 Why were power chucks developed? 23.4 Why can (a) boring on a lathe and (b) tapping be
difficult operations? 23.5 Why is there more than one turret in turret
lathes? 23.6 Describe the differences between boring at work—
piece on a lathe and boring it on a horizontal boring mill. 23.7 How is drill life determined? QUALITATIVE PROBLEMS i 23.15 Explain the reasoning behind the various de—
sign guidelines for turning.
23.16 You will note that we have used both the terms “tool strength” and “tool-material strength.” Do you
think there is a difference between them? Explain. C 23.17 )Explain why the sequence of drilling, boring, «and reaming produces a hole that is more accurate than
just drilling and reaming it. 23.18 Explain why machining operations may be
necessary even on net—shape or near—net—shape parts
made by precision casting, forming, or powder—
metallurgy products. 23.19 What are the consequences of drilling with a
drill bit that has not been sharpened properly? 23.20 A badly oxidized and uneven round bar is being turned on a lathe. Would you recommend a small or a large depth—of—cut? Explain your reasons. 23.21 Describe the problems, if any, that may be en- countered in clamping a workpiece made of a soft
tn . . in, a three-jaw chuck. ,v Does the force or torque in drilling change as
"'ole depth increases? Explain. 23.23 Explain the similarities and differences in the
design guidelines for turning and for boring. 23.24 What are the advantages and applications of
having a hollow spindle in the headstock of a lathe? 23.25 Explain how you would go about producing a
taper on a round workpiece on a lathe. - und Shapes: Turning and Hole Making W Nag U03 23.8 Why are reaming operations performed? 23.9 Describe the difference between a steady rest
and a follow rest. Give an application of each. 23.10 Explain the functions of the saddle on a lathe. 23.11 Describe the relative advantages of (a) self-
opening and (b) solid—die heads for threading. 23.12 How is a boring mill different from a lathe? 23.13 Explain how external threads are cut on a
lathe. 23.14 What is the difference between a blind hole
and a through hole? What is the significance of it? 23.26 Assume that you are asked to perform a boring
operation on a large-diameter hollow workpiece.
Would you use a horizontal or a vertical boring mill?
Explain. 23.27 Explain the reasons for the major trend in pro-
ducing threads by thread rolling versus thread cutting.
What would be the differences (if any) in the types of
threads produced and their performance characteristics? 23.28 In some materials the hole drilled can be small-
er than the diameter of the drill. Explain this phenome—
non and identify the relevant material properties that
could influence it. 23.29 Describe your observations concerning the con-
tents of Tables 23.2 and 23.4 and explain why those
partigular recommendations are made. We have seen that cutting speed, feed, and -of-cut are the main parameters in a turning op— eration. In relative terms, at what values should these parameters be set for a (a) roughing operation and (b) finishing operation? 23.31 Explain the economic justification for purchas- ing a turret lathe instead of a conventional lathe. 23.32 The footnote to Table 23.11 states that (in
drilling) as the hole diameter increases, speeds and
feeds should be reduced. Explain why. 23.33 In modern manufacturing with computer-con-
trolled machine tools, which types of metal chips
would be undesirable and why? @ List and explain the factors that contribute to "in surface finish in the processes described in this
chapter. 23.35 The operational severity for reaming is much
less than that for tapping, even though they are both in—
ternal material-removal processes which can be difficult.
Why? 23.36 Review Fig. 23.6 and comment on the factors
involved in determining the height of the zones (cutting
speed) for various tool materials. 23.37 We have stated that some chucks are power ac-
tuated. Make a survey of the technical literature and
describe the basic design of such chucks. 23.38 What operations typically can be performed on
a drill press but not on a lathe? QUANTITATIVE PROBLEMS ; @Calculate the same quantities as in Example 23.1 for igh-strength titanium alloy and at N = 800 rpm. .xgam ”23.4Z\Estimate the machining time required to rough
turn a 0.4—m long, annealed copper—alloy round bar
from 60-mm diameter to 55-mm diameter using a
high—speed—steel tool. (See Table 23.4.) Estimate the time required for an uncoated carbide tool. / #:7».._ 231.7153) high-strength cast-iron bar 5 in. in diameter is mailed on a lathe at a depth-ofvcut d = 0.050 in.
The lathe is equipped with a 15-hp electric motor and
has a mechanical efficiency of 80%. The spindle speed is
500 rpm. Estimate the maximum feed that can be used
before the lathe begins to stall? 23.46 A 0.4-in. diameter drill is used on a drill press
operating at 300 rpm. If the feed is 0.005 in./rev, what is the MRR? What is the MRR if the drill diameter is
doubled? 23.47 In Example 23.4, assume that the workpiece
material is high—strength aluminum alloy and the spin—
dle is running at N = 600 rpm. Estimate the torque re-
quired for this operation. 721 Synthesis, Design, and Projects 23.39 Explain how gun drills remain centered during
drilling. Why is there a hollow, longitudinal channel in
a gun drill? 23.40 Comment on the magnitude of the wedge angle
on the tool shown in Fig. 23.4. 23.41 If inserts are used in a drill bit, is the shank ma-~
terial important? If so, what properties are important?
Explain. 23.42 Refer to Fig. 23.10b and (in addition to the
tools shown) describe other types of cutting tools that can be placed in toolholders to perform other machinv
ing operations. 23.48 In a drilling operation, a 0.5—in. drill bit is
being used in a low-carbon steel workpiece. The hole is
a blind hole, which will be tapped to a depth of 1 in.
The drilling operation takes place with a feed of 0.010
in./rev and a spindle speed of 700 rpm. Estimate the
time required to drill the hole prior to tapping. 23.49 A 3-in. diameter low—strength, stainless—steel
cylindrical 'part is to be turned on a lathe at 600 rpm
with a depth—of—cut of 0.2 in. and a feed of 0.025 in./rev.
What should be the minimum horsepower of the lathe? 23.50 A 6—in. diameter aluminum cylinder 10 in. in
length is to have its diameter reduced to 4.5 in. Using the
typical machining conditions given in Table 23.4, estimate
the machining time if a TiN—coated carbide tool is used. 23.51 For the data in Problem 23.50, calculate the
power required. 23.52 Assume that you are an instructor covering the
topics described in this chapter, and you are giving a
quiz on the numerical aspects to test the understanding
of the students. Prepare two quantitative problems and
supply the answers. SYNTHESIS, DESIGN, AND PROIECTS ; 23.53 Would you consider the machining processes
described in this chapter as net-shape processing (re—
quiring no further processing)? Near-net—shape pro-
cessing? Explain with appropriate examples. —w___1______ _ _____ _.__ - _.._____.M_______ 23.54 If a bolt breaks in a hole so that the head is no
longer present, it is removed by first drilling a hole in
the bolt shank and then using a special tool to remove
the bolt. Inspect such a tool and explain how it works. ...
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This note was uploaded on 11/17/2009 for the course MECHANICAL ME 364 taught by Professor Prof.dr.abdülkerimkar during the Spring '08 term at Yeditepe Üniversitesi.
- Spring '08