Use a cheap caliper to measure off the dimensions from the plans. Define each major diameter by holding the caliper in your left hand and the parting tool in your right. cut in with the parting tool until the caliper slips over the piece. Mark the center of the cove by parting in a little larger than the 3/4" called for. The action of cutting and perfecting the cove will drop in that little bit. Do NOT part in to the ferrule section at this time.
For the ferrule, mark its outer diameter with the caliper and part in to that size.
Trim to the size of the ferrule with the parting tool and part ahead of the ferrule to a diameter less than the inside of the ferrule.
With the exception of the cove and ferrule, bring every part down to its respective diameters.