fix and fit

Files and Filing

by Alex Yoho, ABOM

Though there are hundreds of files available, an optician can get by with relatively few. However, specialized files can make work easier.

Optical files can be broken down into two types: metal, which have finer teeth; and plastic, which have coarser teeth. The cut of the file indicates the coarseness of the teeth, but the length of the file also has a bearing on the coarseness.

ALL-PURPOSE FILING

An average, all-purpose metal file would be a six-inch number 2 double-cut flat file with a “safe edge” on one side. The safe edge is smooth and allows filing right up to an area that you want to avoid filing. I have found “blunt” or parallel to be the best for most optical work.

These files work well for filing the butt of a temple to widen the head space when substituting a generic temple for the original. They can also be used to round off the temple core when converting a skull temple and to prevent the sharp end from catching as the core slides into the cable end.

COARSE AND PLASTIC FILING

■ COARSE FILING. If all of the temple core must be cut off to make the resulting cable temple short enough, you may need to file the first 10 millimeters of the temple shank to become a new core for the cable end. This requires major and well-controlled filing. A coarser file will move metal faster and thus speed the job. To keep from making the core longer than you want, keep the safe edge of the file toward the shank of the temple.
■ PLASTIC FILING. For plastic filing, a double-ended, half-round rasp with tapered ends—typically called a “zyl file—is a good start. These files have a course cut on one end and a finer cut on the other that can cut the butt of a plastic temple, which generally contains both metal cores as well as a plastic shank. Use the smoother end when metal is involved. If the temple butt proves difficult to file because of the metal core, use a coarser file that is made specifically for metal.

SPECIALIZED FILES

There are a few specialized files that can sometimes come in handy.

■ RIFLING FILE. One is a rifling file for rimless screw finishing. This has a small filing surface with a curved-up end to avoid filing the lens. And though it requires very short, painstaking strokes, it will do a nice job with some practice.
■ SCREW-SLOTTING FILE. A screw-slotting file can save the day when a screw breaks off. This is a file that looks a bit like a razor blade and can cut a slot in the screw body itself to allow a screwdriver to back it out for replacement. EB