5.8 Files
D.M. Donner
Files were invented to remove material during the manufacturing process. They are some of the first tools designed to perform this task, and the history of this tool is vast (McGeough & Hartenberg, 2023). Technology has almost eliminated hand files from the manufacturing process with the evolution of more sophisticated cutting tools. However, when performing benchwork, we do not use complicated tooling, so the file finds a nice home here.
Files take a back seat to saws when it comes to material removal, but a saw can not remove material very close to a layout line. This is when we reach for a file. Files are tools made from hardened steel with small cutting edges designed to remove material in small slivers called filings.
As with all machining processes, there are roughing and finishing operations. Filing is no different. There are rough cutting files with aggressive teeth designed to remove as much material as possible per stroke. And, there are files with smaller cutting edges to achieve an accurate and smooth cut.
A simplified explanation of files categorizes them for roughing and finishing processes. The roughing type files are double cut files, meaning the cutting edges are created by a crisscross pattern on the face of the file. This design creates a more aggressive pattern intended for maximum material removal and not for a smooth finish. A single cut file has a single row of cutting teeth much like a saw blade and they remove material in a less aggressive manner than the double cut files.
In the photo above the double cut edges on the left file are obvious next to a single cut file on the right. Having both of these files on hand is necessary for both aggressive material removal used in roughing actions and finer controlled material removal used in finishing actions. The term “bastard” refers to the grade of cut. It is the most aggressive after smooth and second/medium cut grades. For general benchwork activities, bastard cut files work best, and they are the most popular cuts available.
Files are one of the most versatile tools for cutting metal. This is due to their selection of cuts, shapes, and sizes. In the figure above, a small selection of files represents some of the shapes available. The flats on the left are common in 6-12″ lengths in both single and double cut. The square file is nice for cutting features with square corners. The round file can cut radius features into parts. Finally, the triangle file is essential due to the 60° angle that can be used to repair external threads.
The figure above lists the parts of a file. The point is the far end, opposite the heel. The tang is an annealed portion of the file used to attach a handle. Annealing is a process used on hardened parts where the material is softened, in this case by allowing a handle to be threaded onto the tang. The cutting features are located on the face and edge of the file. One exception are lathe files which have safe edges that do not cu