Why is machining so difficult to analyze

1) (3 points) Why is machining so difficult to analyze

For the following show all work. If there is something not included, make an assumption and WRITE it down. 5 points each unless otherwise specified

2) (10 points) I have an unknown material in which I have been asked to turn for an experiment. The people contracting me want to know the shear strength of the material. I measure the cutting force at 400 lbs and the thrust force at 285 lbs. The tool I am using has a rake angle of 8º. The width of cut is 0.210 inches and the chip thickness before the cut is 0.010 inches. If the chip thickness ratio is 0.4 inches what is the shear strength of the material?

3) (10 points) A turning operation is to be performed on a lathe with an efficiency of 85%. The material being machined is an alloy steel with a unit horsepower of 1.6 hp / (in³/min). Cutting speed is 350 ft/min and feed is .012 in/rev. Depth of cut is .010 inches. Can this job be performed on a 10 hp lathe. Show all work.

4) Some tools use coatings that reduce the coefficient of friction. How does this affect the cutting process?

5) What are the three parameters that you as an engineer can affect in a machining operation

6) How does the heat generated during cutting affect the operation?

7) What are the main failure types found in tools (5 of them)? Where do these typically occur on the tool?

8) What properties are desired in a material for a cutting tool?

9) (10 points) In a turning operation the operator obtained a tool life of 10 minutes at a speed of 400 ft/min and a tool life of 50 minutes at a speed of 200 ft/min.

a. What is the tool life at a speed of 100 ft/min?

b. What speed would he have to run if he wanted a tool life of 30 minutes?

10)(10 points) If a bar of SAE 1040 is to be turned with a high speed steel tool with a feed of 0.015″ per revolution, and a depth of 0.050″. Previous experiments have revealed that the following cutting velocities yielded the following tool lives,

90 fpm for 30 min.

80 fpm for 90 min.

75 fpm for 150 min.

a) estimate the cutting speeds to get tool lives of 60 and 120 minutes.

b) calculate the mrr at the two speeds found in part a).

11)(10 points) The parameters in a tool life equation come out to be n = 0.4 and C = 450. What % increase or decrease occurs in the tool life if the speed

a. Is increased by 20%

b. Is decreased by 30%

12)(10 points) You are going to machine a .25 inch hole in a block of 1020 CRS for a depth of .16 inches. Please specify a drill for this and all its parameters. Also specify its feed and speed. Finally give me a cycle time

13)(10 points) You are to machine a piece of bar stock. The material is 6061 aluminum. You are to turn the material from a diameter of .5 inches to .3 inches. Please specify an insert to do this job. Be specific (use the internet) Also specify a feed, speed and depth of cut. The length of cut will be the letters in your last name * (.2). Tell me how long this will take