The Union Butterfield 1785M uncoated, high-speed steel spiral point tap has a relieved-style design, straight flutes with a plug chamfer, and a round shank with a square end, and is used to create right-hand threads in a range of materials. This tool produces ANSI standard threads in metric sizes. 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). Relieved-style tap design reduces the friction between tap and workpiece for reduced tool wear. 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 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 provide an economical alternative to coated tools. 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 1785M tap series, taps with nominal diameters of 2 mm to 8 mm have two flutes and those with diameters of 9 mm to 18 mm have three flutes. All taps in this 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 6H tolerance class: 6H is used for a normal length of thread engagement and medium tolerance quality.
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.