1. A face-milling operation is performed to finish the top surface of a steel rectangular (5) workpiece 12.0 in long by 2.0 wide. The milling cutter has four teeth (cemented carbide inserts) and a 3.0 in diameter. Cutting conditions are v = 500 ft/min, f = 0.010 in./tooth, and d = 0.150 in. Determine
(a) the time to make one pass across the surface, and
(b) the metal removal rate during the cut.
2. A cylindrical work bar with 4.5 in diameter and 52 in length is chucked in an engine lathe and supported at the opposite end using a live center. A 46.0 in portion of the length is to be turned to a diameter of 4.25 in one pass at a speed of 450 ft/min. The metal removal rate should be 6.75 in3 /min.
Determine
(a) the required depth of cut,
(b) the required feed, and
(c) the cutting time. (6)
3. A surface grinding operation is being performed on a 6150 steel workpart, (5) (annealed approximately 200 BHN). The designation on the grinding wheel is 51-C-24-D-5-V- 23. The wheel diameter = 7.0 in., and its width = 1.00 in. Rotational speed = 3000 rev/min. The depth (infeed) = 0.002 in. per pass, and the crossfeed = 0.50 in. Workpiece speed = 20 ft/min. This operation has been a source of trouble right from the beginning. The surface finish is not as good as the 16μ-in. specified on the part print, and there are signs of metallurgical damage on the surface. In addition, the wheel seems to become clogged almost as soon as the operation begins. In short, nearly everything that can go wrong with the job has gone wrong.
(a) Determine the rate of metal removal when the wheel is engaged in the work.
(b) If the number of active grits per square inch = 200, determine the average chip length and the number of chips formed per time.
(c) What changes would you recommend in the grinding wheel to help solve the problems encountered?
Explain why you made each recommendation.
4. A centerless grinding operation uses a regulating wheel that is 150 mm in diameter and (6) rotates at 500 rev/min. At what inclination angle should the regulating wheel be set, if it is desired to feed a workpiece with length = 3.5 m and diameter = 18 mm through the operation in exactly 45 sec.
5. The end of a large tubular work part is to be faced on a NC vertical boring mill. (6) The part has an outside diameter of 38.0 in and an inside diameter of 24.0 in. If the facing operation is performed at a rotational speed of 40.0 rev/min, feed of 0.015 in/rev, and a depth of cut of 0.180 in.
Determine
(a) the cutting time to complete the facing operation and
(b) the cutting speeds and
(c) metal removal rates at the beginning and end of the cut.
6. An electric discharge machining operation is being performed on tungsten. (5)
(a) Determine the amount of metal removed in the operation after one hour at a discharge amperage = 20 amps.
(b) If the work material were tin, determine the amount of material removed in the same time.
Use metric units and express the answer in mm3 . [melting point of tungsten = 3410 C and that of tin = 232 C]
7. The roughing section of a broach is to remove stock 3.2 mm deep from a steel surface, (6) 205 mm long, 50 mm wide, each tooth takes a cut 0.13 mm deep. How long should the roughing section be? What pull must the broaching machine exert if the chip pressure is 4 GPa of chip area? Calculate the power required if the cutting speed is 7m/min.
8. A slab-milling operation is being carried out on a 12 in. long, 4 in. wide (6) annealed mild steel block at a feed f = 0.01 in/tooth and depth of cut d = 1/8 in. The cutter is D = 2 in. in diameter, has 20 straight teeth, rotates at N =100 rpm and is wider than the block to be machined. Calculate the MRR, estimate the power and torque required for this operation and the machining time. Unit horse power = 1.1 hp/in3 /min
9. Multiple choice: (5) a) End milling is most similar to which one of the following?
(a) face milling, (b) peripheral milling, (c) plain milling, or (d) slab milling.
b) A broaching operation is best described by which one of the following? (a) a rotating tool moves past a stationary workpart, (b) a tool with multiple teeth moves linearly past a stationary workpart, (c) a workpart is fed past a rotating cutting tool, or (d) a workpart moves linearly past a stationary single-point tool.
c) A facing operation is normally performed on which one of the following machine tools: (a) drill press, (b) lathe, (c) milling machine, (d) planer, (e) shaper.
d) Which of the following abrasive materials is most appropriate for grinding nonferrous metals (one best answer)? (a) aluminum oxide, (b) cubic boron nitride, (c) diamond, or (d) silicon carbide. e) Which of following results in higher material removal rates? (a) larger grain size, or (b) smaller grain size.