In mild steel tube you can run that 1" cutter at least 760 rpm, depending upon the grade of inserts, so if that is high enough to get you some torque... you will have to see.

Doesn't matter what tube diameter you want to use, just be centered over it in the Y direction. The code I just gave you was wrong, too early in the morning and my math was bogus. OK, you want .75 radius, minus 1/2 the cutter diameter, so .25 is the amount off center to swing the arc. Just change it to:

G00 X1 Y.25
G01 Z-1.6
X0
G03 Y-.25 J-.25
G00 X1
Z1

You are stating the arc radius with the J value, it is the value from arc start to arc center, at the centerline radius of the end mill's path. In this case .25" plus half the cutter, .500" is going to give you the .75" radius you want.