Hand Files Technical Information
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Basics of... Hand Files
How to Choose the Right File
File selection depends on the size and contours of the item being shaped. It's also based on common sense and personal preference. To achieve the desired results, the user should first consider the work to be done, then select the appropriate size, coarseness, tooth type and shape of the file.
The size and the coarseness of a file are directly related. Larger files are relatively coarse; they remove more stock, but leave a rougher finish. Smaller files are finer; they remove less stock, but leave a smoother finish.
Once file size and coarseness have been determined, tooth type should be selected. Generally speaking, double-cut files should be chosen for the fast removal of stock, while smooth double-cut or single-cut files should be used for finishing.
File shape is extremely important in determining the final contour of the workpiece. A triangular file should be used on acute internal angles to clear out square corners and to sharpen saw teeth. A flat file should be used for general purpose work, a square file for enlarging rectangular holes and a round file for enlarging round holes. A half-round file can be used for dual purposes - the flat face for filing flat surfaces and the curved face for grooves.
Parts of a File
File Terminology:
Back: The convex side of a half-round or other similarly shaped file.
Edge and Safe Edge: The side surfaces of a file; may be smooth (safe edge) or have teeth.
Handle: A holder into which the tang of the file fits. If the file has an integral holder this is known as a solid handle file.
Pinning: Filings wedged between the file teeth.
Shelling: The breaking of file teeth, usually caused by using too much pressure, reverse filing, filing sharp corners or filing edges.
How a File Works: Tooth Type and Coarseness
Two different attributes determine how aggressively a file will remove material and how smooth a finish will result: the kind of teeth that have been cut into the file and the coarseness of those teeth. The work to be accomplished - roughing or finishing - will determine the kind of teeth and grade of coarseness best for each application.
Kinds of Teeth
Single-Cut Teeth: Has a single set of parallel, diagonal rows of teeth. Single-cut files are often used with light pressure to produce a smooth surface finish or to put a keen edge on knives, shears or saws.
Double-Cut Teeth: Has two sets of teeth positioned diagonally on the file face at opposite angles to each other. The double-cut file is used with heavier pressure than the single-cut for faster material removal.
Rasp-Cut Tooth: Commonly known as a rasp, has a series of individual teeth formed by a single-pointed tool. A rasp produces a rough cut and is used primarily on soft materials such as wood, hooves, aluminum and lead.
Curved-Cut/Milled Tooth: Has its teeth arranged in curved contours across the file face. Curved-cut tooth files are often used in automotive body shops for smoothing body panels.
Coarseness
Swiss Pattern Files are smaller in size and finer in coarseness than their American Pattern counterparts. Swiss Pattern Files are used for more precise and intricate work.
Most American pattern files are available in three grades of coarseness: bastard-cut, second-cut and smooth-cut. The degree of coarseness increases with longer file length, but the differences between bastard, second and smooth-cut remain proportionate.
Swiss pattern files are available in seven grades of coarseness: 00, 0, 1, 2, 3, 4, and 6. As with American pattern files, the degree of coarseness of Swiss pattern files increases with length, but the difference between grades remains proportionate.
File Shapes
Type or shape describes the cross-section shape of the file, i.e., rectangular, square, round, half-round, triangular, etc. The area to be filed will determine the specifictype to be used. Type is further classified according to the contour of the file: blunt or taper.
A blunt file has a constant width with edges parallel from end to end. It is used when the item being filed is very uniform or consistent so only one size file is needed.
The cross-section of a taper file decreases from its heel to its point; it may taper in width, thickness or both. A taper file allows the user to vary the size of the filecontact area without actually changing files. It is useful when the workpiece is more complex, presenting different filing needs.
How to Use a File Correctly
Standard Grip: For files needing two-handed operation, the handle should be grasped in one hand and the point of the file in the other hand. The file handle should berested in the palm with the thumb pointing along the top of the handle and the fingers gripping the underside. The point of the file should be grasped between thethumb and the first two fingers with the thumb being on the top of the file.
Heavy Stroke Grip: When heavy filing strokes are required, the thumb on the point is normally in line with the file; the tip of the thumb pointed forward.
Light Stroke Grip: For lighter strokes, the thumb can be turned to as much as a right angle to the direction of the stroke.
If the file is being used one-handed for filing pins, dies or edged tools not being held in a vise, the forefinger, and not the thumb, is placed on top of the handle in linewith the file.
For normal flat filing, the file should be moved forward on an almost straight line of a single plane, changing its course only enough to prevent grooving.On the reverse stroke, it is best to lift the file clear of the workpiece, except on very soft metals. Even then, the pressure should be very light - never more than theweight of the file itself.
For normal filing, the vise should be about elbow height. When there is a great deal of heavy filing, it is better to have the work slightly lower. If the work is of a fineand delicate nature, the work can be raised to eye level.
File Care
The teeth of the file should be protected when the file is not in use by hanging it on a rack or keeping it in a drawer with wooden divisions. Files should always be keptclear of water or grease, since this impairs the filing action. It is advisable to wrap the file in a cloth for protection when it is carried in a toolbox.
The file teeth should be kept clean at all times by using a file card, or a wire file brush, to clear the grooves between the teeth.
A file should never be used without a tight fitting handle. Serious accidents can result if the handle becomes detached exposing the sharp point of the tang.
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