File Under Useful

by Dan Thompson

Three-square, half-round bastard, and rat tail all sound like names you would call your ex, but they also are commonly applied to hand files. The difference is that these are actually the names of the tools instead of expressions of disgust. Considering the imagination that goes into classifying files, perhaps it is not surprising that there is confusion about what they are for and how to use them. In the hopes of demystifying this incredibly useful tool, here is a quick guide to hand files: how to pick them, how to use them, and how to care for them.

Hand files are nothing more than pieces of tool steel with teeth cut into them, much like a saw, and come in an astounding variety of shapes and sizes. Miniscule escapement files shave off the smallest fragments of materiel while two foot long mill files move several millimeters of steel with one stroke. Files can be flat, round, bladed, or, in the case of rifflers, oddly curved to get into tight places. Files can cut any material softer than themselves, which includes nearly everything. Metals, woods, plastics, and wax are all on the menu, along with some rocks and minerals. All of these and more can be shaped, sized, sharpened, and smoothed with incredible accuracy using minimal skill.

Different situations call for different files, depending on the shape, type, and amount of material that needs filing. Picking the right file for the job can be confusing, but there are only two basic considerations: shape and coarseness. For the first of these, pick a shape that will work best on the surfaces that are to be filed. Don’t try to use a wide, flat file on a convexly curved surface, and don’t use a round file on a concave surface. Use extra wide files for smoothing large areas, but pick tiny, tapering shapes to get into close spaces.

Determining the coarseness of a file’s teeth can be difficult thanks to the amazing inconsistency between companies in designating tooth size. To begin with, there are two major systems for rating file cut. The one used by most file makers in the U.S. runs as follows, from coarse to smooth: rough, coarse, bastard, second cut, smooth, and dead smooth. Swiss file makers, however, use a numerical system, with the coarsest designated 00, followed by 0, 1, 2, and so on. Some companies manufacture files with #10 cut teeth, which leave a finish equivalent to 600 grit sandpaper. Be aware, though, that neither of these systems is completely standardized, and file cut will vary from company to company.

Also, consider single versus double cut files. While single cut files have teeth cut in only one direction, double cut files have a second row of teeth cut across the first, which moves material quicker and keeps files from getting ‘gummed up.’ On the other hand, single cut files leave a much smoother finish. Single cuts are also more appropriate for certain filing techniques, such as draw filing.

While there is no end to the variety of file types, some are more useful than others. The most utilitarian file has a half round profile and moderate coarseness- with one flat side and one rounded, this profile is good for a variety of surfaces. Another excellent file is the handy file, made by the Nicholson File Company. Originally intended for sharpening lawnmower blades, it certainly lives up to its name, offering double-cut coarse teeth on one side and single-cut smooth teeth on the reverse. Also, one thin edge of its rectangular profile has smooth teeth while the other is a toothless safety edge. This allows the file to grind sharp right angles with one side while the other can work right up to the edge of a piece without damaging any adjoining material.

Despite their range of shapes and sizes, nearly every single file has one thing in common: they only cut in one direction. The teeth are raised facing forward, so they cut when the file is pushed forward from the handle. Too often people use files like some sort of magic wand or eraser, scrubbing away at material with no real effect. In general, the most efficient method of filing looks like this: place the tip of the tool on whatever needs filing while holding it by the handle with one hand and resting the other on the top end. Push forward and down to cut. Once you’ve reached the handle, stop putting pressure on the file and lightly slide it all the way back, then repeat. Keeping downward pressure on as you pull the file back is a waste of effort, so only push down while going forward. Rubbing the file from side to side is a complete waste of time.

There is nothing better than feeling the bite of a sharp file as you push it across a piece of metal, and a well cared for file will cut like this for decades. On the other hand, refurbishing a dull or rusty file is nearly impossible, so putting a little effort into maintaining that $60 Friedrich Dick file is worth the effort. To keep them sharp, make sure to not let files come in contact with anything as hard as or harder than they are. First on this list are other files. Storing them dumped together in a drawer is one of the best possible ways to ruin files, so don’t do it. Ideally, keep them hanging from their handle or stored in individual slots in a piece of wood. Also, sandpaper, drill bits, and other tools made out of high speed steel should not touch a file’s teeth, nor should you bother trying to file these materials. Use a grinding wheel instead.

It may take a bit of practice to reach the skill level of fine jewelers and watch makers, but files are simple enough to use even if you aren’t a master. Their versatility makes them indispensible in any toolbox, and, properly cared for, they will last a lifetime.