Types of common taps.
Special purpose taps.
(5) Boiler taps. Straight boiler taps (fig 30) range in diameter from 1/2
to 1-1/2 inches, The chamfered portion of the thread simplifies starting. Taper
boiler taps have no chamfered portion and the threaded portion is tapered 3/4 inch
per foot. The overall and shank diameters are similar to those of straight boiler