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EML 4321  HW #9  Due start of class 23 March
1.
You are to broach a keyway for a square key into a 1” diameter drilledandreamed
hole in the center of a gear’s hub.
The gear’s hub is 1.6” thick.
The keyway is to be ¼”
wide.
The material is 200 HBN grey cast iron.
The roughing teeth on the broach have a
step of 0.005” per tooth and are spaced 3/8” apart.
The broaching is to occur at 80 SFM.
a.
What is the average number of teeth cutting simultaneously?
b.
What is the maximum number of teeth cutting simultaneously?
c.
What is the average force required to push the broach?
d.
What is the maximum force required to push the broach?
e.
What speed (ft/min) should the broach be pushed at?
f.
What is the average power (HP) required during broaching?
g.
Assume half of the depth of the keyway to be cut is into the hub (Hint: ¼”/2) and there
is an additional allowance of 0.050” to allow for errors and hole rounding, how many
roughing teeth are required on the broach?
h.
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 Spring '08
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