Machining Steel - Design and Manufacturing Engineering - Lecture Notes, Study notes for Design and Analysis of Algorithms. Allahabad University

Design and Analysis of Algorithms

Description: These are the Lecture Notes of Design and Manufacturing Engineering and its key important points are: Machining Steel, Face Turning, Machining Operations, Chamfering, Adequate Side, Cutting Edge, Tool Post, Tool Holder, Minimize Damage, Tool and Tool
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“Machining Steel”
A Lab in Two Parts
Part A
Equipment: Lathe w/ tool post
Single point Triangular Carbide Cutter
Positive Tool Holders
CR 1018 Steel Workpiece (1" (25.4 mm) diameter -- Center Drilled)
During this laboratory the student team will produce the part “Adjuster Leg” shown on
the attached sheets. The machining operations required will include longitudinal turning,
"chamfering", and face turning (facing) during Part A. The cutting tool should be positioned
with an adequate side cutting edge (lead) angle to allow free cutting operations, we will be using
both right hand and left hand cutters to perform each operation. Note the tool’s positive rake
angle and clearance angles. The chips as they are produced will slide over the rake face away
from the work when properly mounted. Also, the tool post/tool holder is mounted so that any
problems in the operation tend to eject the tool from the workpiece to minimize damage. After
the tool is mounted, with tool tip on center (or very slightly above center), the tool and tool
holder should be tightened rigidly to the lathe's tool post.
When performing the longitudinal turning operations, the majority of the laboratory, the
student teams most consider the appropriate "Process Plan." Typically, the operation will follow
a series of passes. Starting with "Roughing" operations of high feed, large depth of cut (doc) and
moderate speed, through semi-finishing to final finishing operations employing small feeds and
doc of 0.005 to 0.0075 [0.127 - 0.191 mm] and high(er) speeds. Specific machining
recommendations for CR 1018 steel are found in the Machining Data Center Machining
Handbook. For each of your group's machining passes calculate the cutting speed and/or RPM
rate, metal removal rate (MRR), cutting time and ideal surface finish generated -- formulae in
handout shown below. These calculations should be tabulated in your group lab report to be
submitted after Part B. During production machining operations, often the processes,
particularly the roughing operations, are designed to minimize cutting time by maximizing the
consumed horsepower in making a cut. Most metals exhibit a constant Specific Horsepower in
units of: HP/in3 (a minor function of MRR). The specific horsepower for 1018 CR steel using
sharp cutters is about 1.1HP/in3. Using this value and the MRR's calculated above, determine the
power requirements of your actual operations based and compare it to the available motor
horsepower of the lathe being used.
During facing operations, setup the operation using a left handed tool holder and employ
the power cross feed mechanism. During these operations, consider the effect of the turning
diameter on MRR as your tool cuts on the face. Tabulate MRR at full diameter, "half radius,"
"quarter radius," and the center of the bar.
During each machining pass, observe and describe the chips being produced, include this
information in your lab notebook. Observe and describe the surface finish (Ra) produced in each
operation as well. Observationally, does the finish correspond to your calculated value using the
equation below:
Measure and report, employing a dimensioned drawing, the geometry of the part your team
actually produced. Keep your finished part, it will be used for Part B.
Part B
Equipment: Lathe w/ tool post
Single point HSS Cutter
60° Threading Cutter
Threading Gage
5/16” 18 NC Tap and Appropriate Drill and driver
Threading Micrometer
CR 1018 Steel Workpiece
During this laboratory the student team will produce the finished adjuster leg part as seen
in the attached print. The machining operations required will include drilling, tapping, and tread
cutting. The cutting tools should be positioned to allow free cutting operations during all
operations. Note the tool grind of a positive rake angle and clearance angles on the 60°
threading tool. The tools should all be mounted with tool tip on center and the tool and tool
holder tightened rigidly to the lathe's tool post and tail stock during processing.
During external threading operations, we will use the “29°” Compound Feed
methodology discussed in reference materials authored by DeGarmo,Black & Kosher (pp. 886-
890) to produce the 5/8x18 NF threaded end of the part. Here the student teams will calculate
the required compound infeed distances for the 60° point to cut the threads. In addition the
teams should monitor and record the chips produced and the effect of chip loading on the
process. Refer to chapter 30 in the reference for details on thread geometry and manufacturing
Y = 8CR
Y is surface deviation
isfeedrate, CR cutter nose radius, average roughness
While machining the internal threaded hole, the team will employ a “gun tap” designed to
produce the required thread geometry. This tap pushes the chips ahead of the tool to assure
cleaner threads during the process. Thus, we need to provide additional length in the drilled hole
to accommodate these chips during the tapping operation. The teams will be expected to
calculate/specify the proper drill to produce the "pilot hole" before tapping. Special care should
be employed during tapping so as not to fracture the tool and scrap your part.
Before beginning the lab, think SAFETY. Metal cutting is a process that can be very
dangerous, you must WORK to perform the tasks as safely as possible. Follow the established
rules and REMEMBER, don't grab any fresh chips with your bare hands and definitely do not
leave the chuck key in the chuck after using it!!!
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