The Union Butterfield 4588 high-speed steel left-hand spiral (helical) flute taper pin reamer is an uncoated (bright) round shank tool commonly used for reaming holes that are intended to receive taper pins, particularly in difficult or long-chipping materials. This tool is often used in a drill press, screw machine or lathe.
A taper pin is a standardized tapered fastener that has a slightly larger diameter at one end than the other so that it can be inserted into a reamed, correctly tapered hole, creating a tight connection due to friction. Some taper pins have threaded ends to receive nuts. Helical flutes can create an exceptionally smooth surface finish because their highly angled spiral allows for maximum surface contact and easier chip removal, thus reducing vibration and finish scoring. All spiral reamer construction, including helical construction, prevents whole-flute contact with the leading edge in an interrupted cut, as in a keyway. This reduces the possibility of damage to the interruption and to the reamer flute. 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.
The number of flutes on a reamer depends on the cutting diameter of the tool. Reamers in this series with taper pin sizes 7/0 to 3/0 have two flutes, those with sizes 2/0 to 8 have three flutes, and those with sizes 9 and 10 have four flutes.
Reamers are used to finish existing holes. When holes are created using common applications such as 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.