5. Files

In order to carry out the many filing operations necessary in metalwork, a wide variety of files is made in different lengths, sectional shapes and grades of cut.

Files

FIles are used in benchwork for tasks such as shaping, smoothing, fitting, and deburring. It is essential to learn how to properly use files when filing is a more practical method than a machine tool. Files are available in a multitude of shapes, sizes, and styles for different applications.

Files can be classified according to:

Length - measured from the heel to the tip of the file
Cross section - Flat, Square, Round, Half Round, Three Square, Mill, Pillar and Knife
Cut or tooth type -
- - - Single cut - have a single set of teeth
    - Double cut - have a second set of teeth perpendicular to the first set. Used for faster removal of material.
    - Rasp - Large teeth, uncommon in machining as it is used to quickly remove soft material like timber.
Coarseness - From coarsest to smoothest, Rough, Bastard, Second-cut, Smooth and Dead Smooth.

File Selection

When selecting files, longer, coarser, double-cut files are generally chosen to remove material quickly, while shorter, finer, single-cut files are generally chosen to create smoother finished surfaces. With practice and experience, you will begin to develop a sense of what type of file to use for different situations, since every job is unique.

As you use files, their teeth will eventually become clogged with the materials you are removing. This is called loading. Sometimes, particularly on softer metals such as aluminium, particles of the material being filed called pins can embed in the teeth. This is called pinning. Pinning and loading will occur more quickly if you use too much pressure. Clear your file frequently to keep pins from scratching the workpiece. If you notice scratches in the material, it's a sign that you need to clean your file. File cards are brushes used to clean files. A file card can have short soft or wire bristles. Many of them also have a small pick that can used for removing pins. To remove the pins, use the pick and slide it between the teeth to push out the pins. Move the brush parallel with the angle of the teeth.

Length

Lengths range between 100 mm and 450 mm, but 150 mm, 200 mm and 250 mm will be adequate for most school workshop applications.

Grade

Grade refers to the size of the teeth. The following grades of file are the most commonly used — bastard, second cut and smooth.

Cut

Most engineers' files are double cut, but mill saw files, which are single cut, are also used for general metalwork.

Sectional Shapes

Flat

Hand

Warding

Useful for working in narrow slots

Square

For filing out small square holes in which large rectangular section files will not fit. Also for 90° V grooves.

Triangular (Three Square)

For filing acute angled corners between and 60° and 90°.

For 60° V grooves.

For filing the sides of small square holes.

Round

For enlarging small diameter holes in which half round files will not fit. Also for small radius curves and U-section grooves.

Half Round

For filing concave curves and large diameter holes.

Useful in corners less than 60°.

When filing a concave curve or large diameter hole, as the file is pushed across the edge twist the wrist to rotate the file slightly and sweep it sideways over the curve.

Pinning or clogging of files

When filing, particles of metal sometimes become firmly wedged in the file teeth and, unless they are removed, make deep score marks on the surface of the work.

To remove 'pins' use a file card, brushing in the direction in which the teeth are cut. Obstinate particles may be removed by sliding the point of a scriber along the cut across the file. Pinning can be reduced by lightly rubbing the file with chalk after cleaning it.

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