The Union Butterfield 1519(UNC) uncoated, high-speed steel hand threading tap has straight flutes, a plug chamfer, and a pulley-style extended round shank with a square end, and is used to create right-hand threads for long-reach tapping in a range of materials. It is available in ANSI thread specification standard UNC (Unified Coarse). The straight flutes are suitable for threading through holes (extending through the workpiece) and blind or bottoming holes (with only one opening). Pulley taps were originally designed for tapping holes in pulley parts that were difficult to reach; a pulley-style tap has an extended shank so it can reach locations that are inaccessible to regular-length hand taps. The plug chamfer eases tapping at the beginning of the hole and helps maintain correct perpendicular alignment with the workpiece for increased tool life.
Right-hand threads are designed to tighten when the head or nut is rotated clockwise (the most common threading direction). High-speed steel (HSS) is a common general-purpose steel for cutting tools and is compatible with a variety of materials. With no coating or surface treatment, this uncoated tool can be used on a broad range of materials and provides an economical alternative to coated tools. The round shank with square end makes it suitable for hand or power-driven applications. This tool can be used in machines, such as drill presses or lathes, or with hand tools such as tap wrenches.
In the Union Butterfield 1519(UNC) series, all taps have four flutes and plug chamfers. This tap conforms to ANSI standards and can create threads to a depth 1 ½ times its diameter. It is suitable for the ANSI 3B tolerance class: 3B produces close-tolerance fasteners that resist loosening, as in aerospace applications.
Taps produce internal threads in previously formed holes and can be used in machines (such as drill presses) or with hand tools. Common types of taps include hand taps, spiral point taps, spiral flute taps, thread forming taps, and pipe taps. Hand taps (straight-flute taps) collect chips in the straight flutes of the tool; spiral point taps push chips through holes ahead of the tool; and spiral flute taps pull chips back from the tip of the tool, up and out the hole. Thread forming taps, also known as cold forming taps, press rather than cut to create threads in a drilled hole, and no chips are created. Pipe taps create threads in pipes and pipe fittings. Each thread type designates a thread profile and each type is identified with an abbreviation. In the U.S. and Canada, the Unified Thread Standard is the dominant thread type, including UNC (Unified Coarse), UNF (Unified Fine), and NPT (National Pipe Taper) threads, among others.