The Alvord Polk 155-2 left-hand spiral flute taper pin reamer is a round shank tool made of high-speed steel with no finish or coating, and is most commonly chosen for reaming holes that are intended to receive taper pins. Taper pins are standardized tapered fasteners with one end having a slightly larger diameter than the other end, in order to easily enter a reamed hole and hold itself through friction; some taper pins have threaded ends to receive nuts.
Left-hand spiral reamers are useful for interrupted cuts and in through holes. Spiral reamers prevent whole flute contact with the leading edge in an interrupted cut, as in a keyway. This prevents damage to the interruption and reamer flute. Left-hand spiral style tools also push chips ahead of the tip of the tool, instead of pulling chips out of a hole. Left-hand spiral reamers are also useful when reaming through holes, since pushing chips into the hole can cause clogging, which may damage the tool. High-speed steel is a general purpose steel for cutting tools and is compatible with many metalworking materials. It is often lower in price than other cutting tool materials.
For reamers in the 155-2 series with taper pin size 7/0 to 2/0 there are four flutes, for size 0 to 8 there are six flutes, and for sizes 9 and 10 there are eight flutes. Tolerances for machining this reamer series are +.0030 / +.0060 inches.
Reamers are used to finish an existing hole. These holes are often adequate, but in some engineering applications the resulting hole is not round enough or is incorrectly sized, and therefore reaming is necessary. Reaming positively affects the mechanical properties of the hole by producing a hole with an exceptionally smooth finish and precise roundness and diameter. Reaming is often used before tapping screw threads.
Alvord Polk manufactures a broad family of cutting tools, brushes, and tooling components, following ISO 9001 standards for quality and environmental impact of their products. Their offices and manufacturing facilities have been located in the United States since 1881.