When I started out, I set the compound to 29+-. Then watched Joe Pie's YouTube video on threading. Made perfect sense. At anything less than a perfect 30* the tool will not be taking a big enough bite to cut on the one side. Result will be rubbing, burnishing, heating. On external threads I have good results, cutting tool upside down and cutting away from the chuck. No crazy fast moves required. I've been cutting all of my external threads that way and get good results, if I'm using metal that machines well. This morning I sharpened my HSS internal threading tool. Put a bit more relief on. Now to make the test part and see if I can sneak up on a fit for the internal part.
If I get the internal threading down, my next project is a spider for the out-board end of the spindle.
If I get the internal threading down, my next project is a spider for the out-board end of the spindle.