The Union Butterfield 4600 high-speed steel left-hand spiral flute taper pipe reamer is an uncoated (bright) round shank tool with a square end; its standard size and 3/4" per foot taper make it suitable for reaming holes that are to be tapped with National Pipe Taper (NPT) threading. This tool is often used in a drill press, screw machine or lathe. It can be used with cast iron, steel, brass, and most ferrous and non-ferrous materials.
Using a taper reamer prior to tapping with taper taps provides threads of better quality. Taper pipe reamers in this series are recommended for tapping any NPT threading: Dryseal or Military Aeronautical Pipe Thread (ANPT) specification. Spiral flute reamers are useful for interrupted cuts because they prevent whole flute contact with the leading edge of an interrupted cut, as in a keyway. This prevents damage to the interruption and the reamer flute. Also, spiral flute taper pipe reamers are designed for reaming harder materials where additional shear is needed. Left-hand spiral tools are good for use in through holes (extending through the workpiece) because they push chips ahead of the tip of the tool. High-speed steel (HSS) is a general-purpose steel for cutting tools that is compatible with many metalworking materials. It is often lower in price than other cutting tool substrates. Square-end shanks help prevent rotation in the tool holder. Uncoated (bright) tools have no additional surface treatment or coating; they are suitable for general-purpose applications.
The number of flutes on a reamer depends on the cutting diameter of the tool. Reamers in this series that are 1/8” and 1/4” in diameter have six flutes, 3/8” and 1/2” in diameter have eight flutes, 3/4” to 1-1/2” in diameter have 10 flutes, and 2” in diameter have 12 flutes.
Reamers are used to finish existing holes. When holes are created using common applications like drilling or punching they often have minute imperfections. Their roundness may be flawed, or their diameters may be slightly smaller than required. Reamers are made to exacting tolerances, so they can correct such errors and create precisely round holes with exact dimensions. Reaming is often used before tapping screw threads.