Yes the thread was milled in one pass. At first with a three tooth thread mill- all the teeth in line, which meant my part had to rotate enough times to get the
thread length correct. But later I got a Kennametal thread milling tool that had eight to ten teeth using an insert. This one would cut the entire thread in ONE revolution, with the rotary table feeding up one thread pitch. ALL of my parts used 16TPI so I didn't have to worry about not having the right leadscrew.
Setting up for milling was not too hard, but with the Vetcoa in it's fully lowered position at 7 3/4 inches, and my parts either being six inches or EIGHT inches, I was really out of room. Even with an Indicol for finding center it was tight. Since I was running the same parts I could make a plug to go in the center hole of the Vetcoa, to line up my part. Getting thread depth wasn't hard. Find the position where the cutter just touches the surface, zero out the DRO and then move over the depth of thread. Do a couple of parts and you're off to the races. My mating parts for the threads, a bearing retainer, were so thin I could use one to check threads without moving anything. After my thread was cut I would move the table over to clear the cutter. Nothing to it. If you weren't deep enough you DO have to allow the Vetcoa to lower, and NOT move the spindle of your machine, or you will lose the lead. The Vetcao is a DC drive machine, and I would bet you could pick up your lead if you were careful however.
I was running my castings on an Excello double end boring machine for the bearing journals and thread ID's and then thread milling. Didn't take very long to realize it's faster and easier to thread these in my CNC lathe after making arbors to match my casting, and the Vetcoa was put away forever. It DID work, it's a VERY nicely made machine. If I didn't have CNC capablities, for certain applications, it's a great tool. I BOUGHT a riser for my Bridgeport, but changed my process before I installed it. If you have parts MORE than eight inches high, figure on a riser or another way to do your threads.
Leadscrews are a VEE thread, I never had to make any.