The Union Butterfield 4500 high-speed steel straight flute hand reamer is an uncoated (bright) round shank tool with a taper lead and a square end; it is commonly used for general-purpose hand reaming. Straight flute reamers are useful for uninterrupted cuts in general-purpose applications. They 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 general-purpose steel for cutting tools and is compatible with many metalworking materials. For alignment, a hand reamer has a relatively long taper lead (compared with a machine reamer, which has a 45-degree bevel lead) to allow the reamer to enter a hole and center itself. A round shank with a square end allows this reamer to be used with a tap wrench, an adjustable hand wrench, or standard tap or reamer chucks. The square end also prevents rotation in the tool holder.
In the Union Butterfield 4500 series, reamers 0.1250” to 0.5312” in diameter have six flutes, 0.5625” to 1.0000” in diameter have eight flutes, and 1.1250” to 1.5000” in diameter have 10 flutes. Tolerances for reamers that are 1/8” to 19/32” tolerances are +0.0001” to +0.0004”; for 5/8” to 1” they are +0.0001” to +0.0005”, and for 1-1/8” and larger they 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.