The Union Butterfield 1528(UNC)/1528(UNF)/1528(UNS) uncoated, high-speed steel three-piece hand threading tap set (including tapering, plug, and bottoming chamfers) has straight flutes and round shanks with square ends, and is used to create machine-screw sized right-hand threads in a range of materials. It is available in three different ANSI thread specification standards: UNC (Unified Coarse), UNF (Unified Fine), or UNS (Unified Special). The straight flutes are suitable for threading through holes (extending through the workpiece) and blind or bottoming holes (with only one opening). Machine-screw sizes are used frequently in many industries and products.
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 1528S(UNC) series, taps that are machine-screw size 1 have two flutes, sizes 2 through 6 have three flutes, and sizes 8 through 12 have four flutes. In the 1528S(UNF) series, taps that are sizes 0 and 1 have two flutes, sizes 2 through 6 have three flutes, and sizes 8 through 12 have four flutes. 1528S(UNS) taps are available in size 4, with three flutes. This tap set conforms to ANSI standards and can create threads to a depth 1 ½ times its diameter. It is suitable for ANSI 2B and 3B tolerance classes: 2B is an average quality fit for commercial and industrial fasteners; 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.
Precision Dormer manufactures cutting tools under the following brands: Precision Twist, Dormer, and Union Butterfield. The company has locations around the world, and provides tools adhering to ANSI, NAS, and DIN standards.