Not All Files Are Created Equal

Anyone who plans on doing more than basic cleaning and maintenance of their firearms will eventually need to smooth or polish a contact point. Whether to slick up a trigger, polish a bolt, or clean up a scratch, metal will need to be removed, and the two main tools used for this purpose are stones and files.

The primary difference between files and stones is that files are generally used to remove metal in greater or lesser amounts, while stones are more commonly used to smooth metal while removing as little as possible. In this article I’m going to focus on files. I’ll cover stones another time.

There are a mystifying array of files available. Hard metal files for steel, soft metal files for aluminum and brass, wood files (often called rasps), and files for more specific materials such as plastic or bone.

File Types

Once the material to be filed is decided, the next question to be answered is "How much metal needs to be removed?" The bite, or coarseness, of the file has to be selected. Files are graded (from roughest to smoothest): rough, middle (or coarse), bastard, second cut, smooth, and dead smooth.

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Files are also rated by their cut. There are single cut and double cut files, and single cut files have one set of angled grooves (called teeth) down their length, while double cut files have two sets that cross at opposing angles. Double cut files can be used with heavier pressure and will generally remove more metal. However, they can also leave a smoother finish.

File Shapes

Next, the shape of the file for a particular job needs to be selected. There are a baffling number of file shapes, from the general purpose pillar file to the very specific 60° or 65° rear sight dovetail file. Some files have one edge ground flat; these are called safe edge files and are designed for work in a small space where only one surface is to be cut.

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To protect our hands, it’s always recommended that a file handle be used. These can be wood, plastic, or rubber, and can be permanently attached or removable. The important thing is that the sharp tail of the file, called the tang, is prevented from being driven into our hand if we slip. A good handle can also give more control when filing.

Proper File Technique

When filing, one of the most important things to remember is that files only cut in one direction. Usually this is from the push, not the pull, meaning it cuts when pushing the handle away as opposed to pulling it back. The recommended technique is to apply pressure to the file as its being pushed, then lift it off the workpiece to bring it back for the next stroke. Using a back and forth motion not only won’t cut any faster, but can damage the file teeth.

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File Care

We’ve all heard the old saying “Take care of your tools, and they’ll take care of you.” This is just as true with files as with anything else.

Before starting a work process that involves files, apply file chalk to the cutting surface. This aids in two main ways: it acts as a dry lubricant when filing, and it makes cleaning the pins (what metal filing residue is commonly called) out of the file teeth. Cleaning files during and after use involves a file brush.

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Cleaning of the file should be done as the teeth become loaded during filing, as pins caught in the teeth can scratch the surface of the workpiece. Once filing is complete, the files should be thoroughly brushed before being stored.

Never put files where they can bump each other, as this can damage the teeth and shorten the useful life of the tool. Instead, store them in separate containers such as plastic tubes. These can be purchased in different sizes and cut to fit the file length. Caps are also available. 

There’s more to proper use, care, and feeding of files, of course, but this should get you started.