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- etc.

66.5 STANDARD PARTS

•Purchased components are typically well designed and inexpensive.

•When you do not have experience designing or manufacturing a certain component, and volumes are low, it may not be possible to produce components at a lower cost than they can be produced.

•These parts must still be considered in the process plans so that they are orders, and arrive in suitable forms.

66.6 PRACTICE PROBLEMS

1.A block of metal 5” by 5” by 5” will be milled to 5” by 5” by 4” and then will have two separate holes drilled 2” deep. The hole will be finished with a reamer.

Part: - Mild Steel Drilling:- High speed steel

-15/32” diameter

-C.S. = 80 ft/min.

-feed = .010” per revolution

-setup time = 5 min. per part

-cost is $40.00 per hour

Reaming:- Carbide Steel

-1/2” diameter

-C.S. = 60 ft./min.

-feed = .015” per revolution

-setup time = 2 min. per hole

-cost is $45.00 per hour Milling:- High speed steel

-C.S. = 100 ft./min.

-cutter diameter = 1”

-10 teeth with a tooth load of .004” per tooth

-setup time = 1 min. per part

-cost is $47.50 per hour

a)Estimate the machining time required to make 50 parts.

b)Estimate the cost of the 50 parts.

c)Estimate the machine horse power required for the drill, reamer and the mill.

2.Calculate the machine tool spindle speeds for the following:

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a)Milling with a tungsten carbide tipped face cutter on a stainless steel work piece. C.S. = 65 m/min., cutter dia. = 150mm.

b)Drilling with a High Speed Steel drill in Machine Steel work, with C.S. = 70 ft./min., and a drill diameter of 19/32”

c)Turning on a lathe with a High Speed Steel tool in a mild steel work piece. Surface cutting speed = 100 ft./min., and a workpiece diameter of 2.75”

d)Milling with a High Speed Steel cutter in tool steel work with a cutter speed of 60 ft./ min., and a cutter diameter of 3/4”.

3.The part below has three turned diameters, on one end there is a square tang that has been milled. The part is made of aluminum. (Note: R indicates radius)

R1.00”

R0.75”

R0.30”

0.25”

0.75”
					1.20”

2.30” 0.50”

0.25”

a)Write a process plan that describes the operations necessary to produce the part.

b)If the milling cutter is a 1/2” diameter end mill with 6 teeth, determine a reasonable feed and speed for cutting the tang.

c)What are reasonable speeds and feeds for turning the part for rough and finish turning? (Note: pick one cut for your calculations)

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ans.	a)	0010 Cutoff stock with dia. 2 1/4” by 4”
		0020	Mount 0.75” in 3 jaw chuck
		0030	Face end and turn down to 2” dia. for 2.8”
		0040	Turn in chuck and face to length
		0050	Cut the taper with a taper cutting attachment
		0060	Use a slot cutter to cut the 0.25” slot 0.4” below the taper
		0070 Mount upright in vise in mill
		0080	Use endmill to cut around the tang

		500 + 1000		ft
b)	CS =	--------------------------2		--------	fpt = 0.011in
				= 750min
	RPM =	12CS	= 5730		F = fpt( teeth) RPM = 378 in
		-------------π D
								min
c)	Rough				Finish
		ft				ft
	CS = 200min--------					--------
					CS = 300min
	0.015 + 0.030			in	0.005 + 0.010			in
	F = --------------------------------	2		= 0.023 rev------	F = --------------------------------	2		= 0.008rev------
	RPM =	12-------------CS	= 382		RPM =	12-------------CS	= 573
		π D				π D

4. Develop a process plan for the part below. You should include speeds, feeds and times. Hint: The part will be easy to make if a combination of milling, drilling and turning is used.

R1.75”

Hole bored to 1.50” depth

R1.25”

1.00”

1.00”

1.00”

1.50”	4.00”

Mat’l aluminum

5.00”