Machine Shop Work: Bench Work No. 8: Fundamentals of Filing

“Gives beginners in shop work the information that will enable them to select the right file for the right job. Defines the terms used, distinguishes the various kinds of files, and indicates the general type of work that each kind of file does best.”

Originally a public domain film from the Library of Congress Prelinger Archives, slightly cropped to remove uneven edges, with the aspect ratio corrected, and one-pass brightness-contrast-color correction & mild video noise reduction applied.
The soundtrack was also processed with volume normalization, noise reduction, clipping reduction, and/or equalization (the resulting sound, though not perfect, is far less noisy than the original).

https://en.wikipedia.org/wiki/File_(tool)
Wikipedia license: http://creativecommons.org/licenses/by-sa/3.0/

A file is a tool used to remove fine amounts of material from a workpiece. It is common in woodworking, metalworking, and other similar trade and hobby tasks. Most are hand tools, made of a case hardened steel bar of rectangular, square, triangular, or round cross-section, with one or or more surfaces cut with sharp, generally parallel teeth. A narrow, pointed tang is common at one end, to which a handle may be fitted.

A rasp is a form of file with distinct, individually cut teeth used for coarsely removing large amounts of material.

Files have also been developed with abrasive surfaces, such as natural or synthetic diamond grains or silicon carbide, allowing removal of material that would dull or resist metal, such as ceramic…

History

Early filing or rasping… has prehistoric roots and grew naturally out of the blending of the twin inspirations of cutting with stone cutting tools (such as hand axes) and abrading using natural abrasives, such as well-suited types of stone (for example, sandstone). Relatedly, lapping is also quite ancient, with wood and beach sand offering a natural pair of lap and lapping compound…

The Bronze Age and the Iron Age had various kinds of files and rasps. Archaeologists have discovered rasps made from bronze in Egypt, dating back to the years 1200–1000 BC…

During the Middle Ages files were already quite advanced, thanks to the extensive talents of blacksmiths. By the 11th century, there already existed hardened files that would seem quite modern even to today’s eyes. But although they existed, and could even have spread widely, in a geographical sense, via trade, they were not widespread in the cultural sense of the word—that is, most people, and even many smiths, did not have them. For example, in the 13th century, ornamental iron work at Paris was done skillfully with the aid of files, but the process was a secret known only to a master craftsman…

Prior to the industrialization of machining and the development of interchangeable parts during the 19th century, filing was much more important in the construction of mechanisms. Component parts were roughly shaped by forging, casting, and by primitive machining operations. These components were then individually hand-fit for assembly by careful and deliberate filing. The potential precision of such fitting is much higher than generally assumed, but the components of such hand-fit assemblies are decidedly not interchangeable with those from another assembly…

Machining in the mid-19th century was heavily dependent on filing, because milling practice was slowly evolving out of its infancy. As late as the early 20th century, manufacturing often involved filing parts to precise shape and size. In today’s manufacturing environment, milling and grinding have generally replaced this type of work, and filing (when it occurs at all) usually tends to be for deburring only…

Files come in a wide variety of materials, sizes, shapes, cuts, and tooth configurations. The cross-section of a file can be flat, round, half-round, triangular, square, knife edge or of a more specialized shape. Steel files are made from high carbon steel (1.0 to 1.25% carbon) and may be through hardened or case hardened.

…A file is “blunt” if its sides and width are both parallel throughout its length. It is “tapered” if there is a reduction in its dimensions from its heel toward its point. A file may taper in width, in thickness, or both. A “tang” is a protrusion at the heel, tapered, parallel sided, or conical, for gripping, inserting in a handle, or mounting in a chuck.

The cut of the file refers to how fine its teeth are… A single-cut file has one set of parallel teeth while a cross-cut or double-cut file has a second set of cuts forming diamond shaped cutting surfaces…

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