The Union Butterfield 1985(UNC)/1985(UNF) high-speed steel spiral point tap has a relieved-style design, straight flutes with a plug chamfer, black oxide surface treatment, and a round shank with a square end, and is used to create right-hand threads in steel, stainless steel, titanium and nickel. It is available in two different ANSI thread specification standards: UNC (Unified Coarse) and UNF (Unified Fine). The spiral point of this tap (sometimes referred to as a “gun tap”) pushes chips ahead of the tool and the straight flutes reduce clogging. Both characteristics make it suitable for threading through holes (extending through the workpiece). The black oxide finish of this tool will not chip. It improves lubricity, resists corrosion, and helps to prevent buildup and welding on the cutting edge of the tool. Relieved-style tap design reduces the friction between tap and workpiece for reduced tool wear. This tap features a high hook, special outside diameter, pitch diameter relief, and increased back taper for free cutting action. A plug chamfer distributes cutting to ease tapping at the beginning of the hole and to maintain correct perpendicular alignment with the workpiece.
Right-hand threads are designed to tighten when a 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. The round shank with square end helps to minimize rotation in the tool holder. 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 1985(UNC) series, taps in machine screw sizes 4 to 12 and those with 1/4” nominal diameter have two flutes, taps with nominal diameters of 5/16” to 3/4” have three flutes, and those with nominal diameters of 7/8” and 1” have four flutes. In the 1985(UNF) series, taps in machine screw sizes 4 to 12 and those with 1/4” nominal diameter have two flutes, taps with nominal diameters of 5/16” to 3/4” have three flutes, and taps with 7/8” nominal diameter have four flutes. All taps in these series have plug chamfers. This tap conforms to ANSI standards and can create threads to a depth 2 ½ times its diameter. It is suitable for the ANSI 3B tolerance class: 3B produces close-tolerance fasteners used for greater resistance to stripping, as in aerospace applications. Sizes ranging from machine screw size 4 to 3/8” nominal diameter are recessed between body and shank for deep-hole 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.