A round file is a wood or metalworking hand tool of cylindrical cross section that is used to remove small amounts of material from a workpiece. Round files typically consist of a long tapered body and a pointed square tang at one end for attaching a handle. The body of the file is cut with a series of parallel ridges which remove material from the workpiece when the file is drawn across it. These files are most commonly used to deburr or remove material from the inside surfaces of cylindrical workpieces or to cut half round grooves. Round files are available in a large selection of sizes and tooth pitches to suit a variety of applications and materials.
Files have been used to shape and finish metal and wood objects for thousands of years; archaeological finds of Assyrian iron rasps, for example, date back as far as 7,000 BC. Although modern machining techniques have largely replaced filing as a primary shaping method, files are still standard hand tools for most professional artisans and hobby enthusiasts. The round file is a fairly specialist type and is used almost exclusively to remove material from the inside surfaces of cylindrical workpieces. It shares a common basic structure with most file types, though, and features a cutting surface and a tapered tang on the opposite end used for a handle attachment. The cutting surface of a round file is elongated, tapered towards its tip, and cut with a series of equally spaced, parallel ridges.
These ridges, commonly referred to as teeth, lend the file the rough, abrasive qualities needed to remove material from the workpiece. The depth and frequency of these teeth dictate the tooth pitch or roughness of the round file. This abrasive grade is known as the cut of the file and is represented by six basic grades: rough, middle, bastard, second cut, smooth, and dead smooth. The cut grade should always be matched to the intended finish required and the material involved.
Some round file designs feature a single series of parallel teeth and are known as cross-cut files. Others feature a second, opposed series of tooth ridges which form a diamond shaped tooth pattern known as a double-cut. Generally the rougher files would be used to remove large amounts of material at the beginning of a project and the smoother examples for final finishing. As with all file types, users should always ensure that the file is fitted with a handle as an exposed tang may cause serious injuries.