SAE threads are straight threads. Some NPT&SAE threads are close enough to screw together, but they probably wont seal under pressure. I have seen NPT threads screwed into holes with SAE threads & vice versa. Did this answer your question? If not holler
NPT threads are a tapered thread, They are tapered 3/4 inch to the foot. I don't know why I know this but I do.
suicidebomb