The Union Butterfield 4536 high-speed steel straight flute chucking reamer (also called a machine reamer) is an uncoated (bright) Morse taper shank tool with a 45-degree bevel lead, commonly used for general-purpose reaming of uninterrupted cuts. Straight flute reamers make small, circular, and precise enlargements to through holes (extending through the workpiece) and blind holes (with only one opening). 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.
Taper shank tools can be self-holding or self-releasing based on the degree of taper: Small tapers are self-holding within a tool holder, while large tapers are self-releasing and will easily release from the tool holder. 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 tool holder. This reamer has a 45-degree bevel at the cutting tip to facilitate entry to pre-drilled holes.
In the Union Butterfield 4536 series, reamers 0.2500” to 0.5312” in diameter have six flutes, 0.5625” to 1.0625” in diameter have eight flutes, and 1.1250” to 1.5000” in diameter have 10 flutes. Tolerances for reamers up to 0.5000” are +0.0002” to -0.0000”; larger than 0.0500” and up to 0.7500” are +0.0003” to -0.0000”; and larger than 0.7500” up to 1.5000” are +0.0004” to -0.0000”. There is an exception for reamers that are dowel-pin sized; their tolerances are +0.0000” to -0.0002”.
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.