Files are used for removing sharp edges on metal and for shaping metal. Files come in a range of sizes, shapes and tooth configurations. Files consist of a handle and a steel blade. The handle will be either made of wood or a tough synthetic material. The blade narrows at one end – the tang – and this fits into the base of the handle. The blade will have parallel ridges running across its width at about 70° from its edge. These ridges are the teeth. Files are classified by the size of the teeth and the space between them. Also whether it has one or two sets of teeth.
A file with just one set of teeth is called a single-cut file. A file with a second set of teeth crossing the first set at a 45° angle is called a double-cut file. Some files will be single-cut on one side of the blade and double-cut on the reverse face.
A file’s teeth will be spaced according to their size: the finer the teeth the closer together they will be. How coarse a file will be indicated by the number of teeth per 25mm (1in).
Bastard file – is a coarse grade file used for initial filing of rough edges and will have 26 teeth per 25mm (1in).
Second-cut file – is a medium grade file used at the beginning of the smoothing process and will have 36 teeth per 25mm (1in).
Smooth file – is a fine grade file used for producing the final smooth finish and will have 47 teeth per 25mm (1in).
When filing you should start with a coarse file, then progress to a finer file to remove the marks that the coarse file will leave on the metal.
A flat file is used for general filing work and is tapered in width and thickness. The blade will have abrasive teeth on both faces and both edges.
A hand file blade will be parallel in width but taper slightly in thickness. Both faces will have abrasive teeth as will one edge. One edge will be smooth to allow you to file close to a corner without causing damage.
These files are rounded on one side, flat on the other and taper towards the tip. Half-round files are used for shaping curves.
The blade of a round file tapers slightly towards its tip. It is used to increase the size of round holes and smoothing the edges of curves.
The blade of a square file is square when viewed in cross-section. It is used to smooth the edges of rectangular holes.
This file has three faces that form a triangle when the blade is viewed in cross-section. The triangular file is excellent for smoothing acute angles less than 90°.
Needle files have extra-fine grades and are often used by jewellers and watchmakers for very delicate work.
Using a file
When using a file the metal you are working on should be held firmly in a vice. It should be held low in the vice to avoid vibration. Keep the file flat and steady by resting one hand on its tip. Make slow forward strokes using the whole length of the file.
Draw filing is a filing action that can be used to create a smooth finish. Hold a smooth finish file with both hands at right angles to the edge of the metal you are working on. Keeping the file flat move the file backwards and forwards on the metal’s edge.