Dz cues,
He is right. If you look up thread milling in the Machinery's Handbook (The Machinist's Bible). It explains it well. Your video clip of the thread grinding shows the correct way. Just because we cut threads on a much smaller scale does not change the theory. A single pont cutter revolving at 30000 rpm is no different than a solid disc as per the large grinding stone. When you thread mill at right angles to your piece you are not accounting for lead of thread. It is just not practical to tilt the axis of your cutter as to your lead. As such we accept the slightly less than perfect thread form. If you think about standard single pont threading where your tool is stationary you always grind a relief on the leading edge of your cutter to account for the lead. You cant do that with live tooling. Having said all that you would have to inspect with a microscope to actualy see the less than perfect form because it is on such a small scale. If you wanted to do it theoreticaly correct than you would have to tilt your cutter on an angle equal to the lead. So with our router set up you would keep the tool parallel to the bore but tilt your cutter front to back. So in other words if you are looking over top of the lathe the cutter or bar is parallel to your bore but lookig at your lathe from the front your router would be tilted at an angle equal to the lead. So having said that your bar would have to be small enough to give you adequate clearance.
He is right. If you look up thread milling in the Machinery's Handbook (The Machinist's Bible). It explains it well. Your video clip of the thread grinding shows the correct way. Just because we cut threads on a much smaller scale does not change the theory. A single pont cutter revolving at 30000 rpm is no different than a solid disc as per the large grinding stone. When you thread mill at right angles to your piece you are not accounting for lead of thread. It is just not practical to tilt the axis of your cutter as to your lead. As such we accept the slightly less than perfect thread form. If you think about standard single pont threading where your tool is stationary you always grind a relief on the leading edge of your cutter to account for the lead. You cant do that with live tooling. Having said all that you would have to inspect with a microscope to actualy see the less than perfect form because it is on such a small scale. If you wanted to do it theoreticaly correct than you would have to tilt your cutter on an angle equal to the lead. So with our router set up you would keep the tool parallel to the bore but tilt your cutter front to back. So in other words if you are looking over top of the lathe the cutter or bar is parallel to your bore but lookig at your lathe from the front your router would be tilted at an angle equal to the lead. So having said that your bar would have to be small enough to give you adequate clearance.