Straight fluted taps(hand taps) are used for threading on lathes, drilling machines and tapping machines. It is the most commonly used tool to tapping through holes or blind holes, non-ferrous or ferrous materials, and the price is the cheapest. 

The lead has 2, 4, 6 thread chamfer, 2P is use for blind holes, and 4-6P for through holes. As long as the bottom hole is deep enough, a longer chamfer (lead) should be used as far as possible, so that there are more teeth sharing the cutting load and a longer tool life.