The Union Butterfield 4532 high-speed steel straight flute expansion chucking reamer (also called a machine reamer) is an uncoated (bright) Morse taper shank tool with a 45-degree bevel lead, commonly used for reaming of uninterrupted cuts in high-production runs on abrasive materials. An expansion reamer can be expanded with a screw as wear decreases its cutting diameter, so it can be reground to its original dimensions and re-sharpened to prevent rapid loss of reamer size or finish.
Straight flute reamers make small, circular, and precise enlargements to through holes (extending through the workpiece) and blind holes (with only one opening). They can be used on a wide variety of materials. High-speed steel is a general-purpose steel for cutting tools that is compatible with many metalworking materials and is often lower in price than other cutting tool substrates. Taper shank tools can be self-holding or self-releasing based on the degree of taper: Small tapers are self-holding within a toolholder, while large tapers are self-releasing and will easily release from the toolholder. The shank end of a Morse taper shank tool is self-holding because friction between the tool and the tool-holder prevents slippage. It is tapered to ensure accurate alignment of the tool in the socket of the toolholder. This reamer has a 45-degree bevel lead at the cutting tip that facilitates entry to pre-drilled holes.
In the Union Butterfield 4532 series, reamers 0.3750” to 0.9688” in diameter have six flutes, 1.0000” to 1.3750” in diameter have eight flutes, 1.4375” to 1.7500” in diameter have ten flutes, and 1.8750” to 2.5000” in diameter have 12 flutes. Tolerances for 0.3750 to 0.9688” reamers are +0.0001” to +0.0005” and tolerances for 1.0000” to 2.5000” reamers are +0.0002 to +0.0006.
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.