Holley fuel bowl thread tap

I have worked on old British bikes, 50's Triumphs that have BS British standard, BSW British standard Whitworth, BSPP British Standard Pipe Parallel, BSPT British Standard Pipe Tapered What a nightmare, and metric has 3 thread pitches, English has fine & coarse. Then there is trying to teach a newbe about threads, they just look at me like I'm crazy.