Just 2 minor comments:
Not all threads have a 60 degree angle (the instruction says to set the compund at 30 degrees).ï¿½ That applies only so far as I know to American UN form and ISO metric form.ï¿½ Whitworth form threads are 55 degrees, so set the compound at 27.5 degrees.ï¿½ Acme is 29 degrees, so set to 14.5 degrees, Metric trapezoidal threads (ISO equivalent to Acme) are 30 degrees, so set to 15.ï¿½ You are unlikely to want to screwcut BA threads (47.5 degrees) as all the thread pitches apart from 0BA (1mm pitch) are difficult to achieve as they and the diameters proceed in a geometric progression, not in nice round numbers in anybody's system.
Setting the compound over at half the thread angle applies only to cutting tools that are not manufactured full form carbide inserts.ï¿½ Single purpose full form carbide threading inserts go straight in.ï¿½
If making a general purpose 55 or 60 degree angle tool for use with feed from the compound slide, only one side will do most or all of the cutting, so the top rake should be a.) suited to the workpiece material and b.) parallel to the direction of feed.
Actually, when cutting ACME or the ISO equivalent, I keep the compound set at 0, so upon achieving the correct measured major & minor diameters and finding the mating thread still tight, I can advance the tool a thour or two at a time longitudinally to widen the groove until it suddenly frees off when tried.ï¿½ I would do the same if I ever had to cut a square thread.
Best wishes to all, and stay healthy,