Trama

Filing is a way of smoothing and shaping material to exact dimensions. It is used in all branches of engineering, from the finishing of heavy castings to the precision work of the aircraft industry. This training film produced in 1941 demonstrates the basic filing techniques and some of the specialist files used for advanced jobs. It is essential to set up the job properly before starting to file. A vice should be used to hold in place the object to be filed, protecting the object from the jaws of the vice using soft metal clamps. To file correctly, the object must be set up square, with the marking line (showing the limits of filing) facing towards you. It is also important to stand properly before starting to file. Stand with the left foot forward and the right foot back, with the body balanced evenly on both feet. Press the handle of the file firmly into the palm of your right hand, with the thumb on top of the file. Like most other cutting tools, using a file with great force will not add to its cutting power. The teeth can cut away the metal only on the outward stroke, so there should be pressure from the left hand on the return stroke. Since pressure from the left hand clogs the teeth with scurf (surface irregularities or imperfections), the file will lose some of its cutting power. Even without applying pressure some scurf will be picked up, so the file should be cleaned using a wire brush after each job. Check the accuracy of the work frequently. A firm stroke in the direction opposite to the previous filing will reveal any high spots as shaded patches. At a more advanced stage of the job, you can test the surface with a straight edge. If the metal is rubbed in red lead or bluing on a surface plate, the high spots pick up the stain. A dead smooth file, for creating a fine cut made is used for the final stage, known as draw filing, which requires a different grip. When filing the rounded end of a metal fitting, known as a radius, you need to use a circular rolling action. For some jobs, a specially shaped file is needed. These include the thin tapered wearing file, the round rat tailed file, the safe-edge file, and the half round file. Prior to attempting advanced filing techniques individuals should master the three rules of basic filing: correct position, correct grip and correct stroke.