Tapping is a machining process for producing internal threads. This article provides a discussion on machines and accessories of tapping. It reviews the seven categories of taps, namely, solid, shell, sectional, expansion, inserted-chaser, adjustable, and collapsible taps, as well as their design and functions. It explains the influences of various factors on the selection of tap design features and discusses the principal factors that influence the selection of equipment and procedure for tapping. The article reviews the factors that determine torque demand. It also provides an overview of tap materials and surface treatment and concludes with a discussion on tapping of taper pipe threads.