Metal works – All you need to know about metal hand files and filing

Choosing the right file can be a very daunting task because there are so many sizes and shapes to choose from. Typical to tool selection, one must select the right tool for the task at hand.


Firstly, it is important to understand the terms used by File manufactures and professional users. Below is a basic diagram with labels outlining all the features of a Hand File. 

Type: The cross-sectional shape or style of the file i. e. quadrangular, circular, triangular or irregular. These sections are further classified according to their contours i. e. blunt, taper etc.

The Shape of the File

The shape of the file is determined by the shape of the workpiece. There is a file for every type of work.

The Shape of the File

Flat File : 

image of a flat file

The Flat is commonly used for general purpose work. They are very useful when it comes to finishing external and internal surfaces. It is also perfect for filling out corners. 

Half Round File:

Image of Half Round FILE tool

The Half Round File is in the shape of a semi-circle it is commonly used for filing internal curved surfaces. 

Round File : 

image of round file

The round file is commonly used for enlarging circular holes as well as filling profiles with fillets.

Square File : 

square file

The Square File is commonly used for filling internal square holes and rectangular openings.

Triangle File / Thre Square File:

Three Square File

The Triangle File is used mostly for filling down corners and acute angles.


Blunt: A file whose edges are parallel from end to end and of constant width.

Taper: The reduction in cross-section of the file from its heel to the point. A file may taper with width, in thickness or in both.

Coarseness: The number of teeth per inch length of the file.

Cut: The character of the file teeth with respect to the coarseness (bastard, second cut and smooth.)

Single-cut file 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.

Which file is ideal?

There are three main factors you should always consider when choosing the right file. These are Shape, Size, and Coarseness of the file. The size of the file determines how much material is removed and the smaller the file the finer the finish.

Most files also have three grades of cut: bastard-cut, second-cut and smooth-cut. The coarser the cut of the file, the rougher the finish of the work. Therefore, the size of the file and the grade of its cut must be taken into account against the amount of stock to be removed and the fineness of finish that is required.

Generally speaking bastard and second-cut grades of double-cut files would be chosen for the fast removal of stock while single-cut files and smooth double-cut files would be chosen for finishing. It is however almost impossible to lay down exact guidelines for the right file for the job, but using the basic facts given here the user should ha v e a reasonably clear picture in mind, the nature, size of the work, the kind of finish required, the working tolerance allowed and the risks (if any) of spoiling the work.

In addition to the amount of stock to be removed, the contour of its removal is equally important and is determined by the shape of the file. For example, a triangular file should be used on acute internal angles, to clear out square corners and in sharpening 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.

3 Main Filing Techniques

Filing is an industrial art – grip, stroke and pressure may vary, to fit the job. There are three elemental ways a file can be put to work They are:

1. Straight filing: Also call cross filing consists of pushing the file lengthwise-straight ahead or slightly diagonally-across the workpiece.

2. Drawfiling: This consists of grasping the file at each end, pushing and drawing it across the workpiece.

3. Lathefiling: This consists of stroking the file against work revolving in a lathe. For normal filing, the vice 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 fine and delicate nature, the work can be raised to eye level. For work that could become damaged in the vice through pressure, a pair of protectors made of zinc, copper or aluminum sheet should be used between the workpiece and vise jaws.

How to file different metals

Different metals vary greatly in character and properties, some are softer than others are, and some are more ductile and so on. The nature of the metal has to be taken carefully into account when choosing the right file and applying it to the job. For instance, a soft ductile metal requires a keen file and only light pressure must be applied during filing if the work is not to be deformed. Conversely, a hard and less ductile metal may require a file with duller teeth to avoid them biting too deep and breaking off when pressure is applied.

When filing a material the user can normally feel whether or not he is using the right file, and filing in the correct manner. All things being correct, a smooth cutting action and a good clean finish on the work is achieved. If there is stubborn resistance, chances are the wrong file is being used, the file is damaged or the wrong method is being used.

Filing rough castings

Snagging castings, removing fins, spurs and other projections is hard on normal files. Their teeth are for fast cutting and do not possess the ruggedness for driving against hard projections and edges. This filing engages only a few teeth, thus putting a strain on each. For such work, it is better to use a Foundry file with sturdier teeth and heavy-set edges to resist shelling or breaking out.

Filing die castings

Like foundry castings, die castings usually have sharp corners, webs, fins or flashing which are liable to damage a normal file. In addition, die castings consist of magnesium, zinc, aluminum, alloy or similar combinations of metal which have the tendency to clog regular files. Depending on the shape, Cooper Hand Tools has a variety of files that will meet the required application. Suggested files are found in the “job by job” file selector of this book, or you may contact your Cooper Hand Tools Customer Service Representative.

Filing stainless steel

The use of stainless steel and alloy steels has created other filing techniques. These steels with hard chromium and nickel content are tough and dense. This causes them to be abrasive, which shortens the life of the normal file. To overcome these problems, files have been developed with good wearing qualities. These files, when used with light pressure and a slow, steady Stroke, will remove metal and provide a good finish.

Filing Bronze (Copper, tin or other alloying elements}

Bronze is similar in nature to brass in some aspects, but varies according to the percentages of alloying elements. Average sharpness of the file is satisfactory for some bronzes, while for others, a file that can maintain its sharpness for longer periods is required. Thus, for the harder bronzes, a file with a more acute angle at the top of the tooth is desirable. This is known as a thin topped tooth. The direction of the stroke of the file should be crossed frequently to avoid grooving with bronze and brass.

Filing Wrought Iron

Wrought iron is relatively simple to file. It is soft but only moderately ductile so it is not necessary for a file to be very sharp to obtain good results.

Filing brass

Brass is difficult to file because it is softer than steel but tough. This demands teeth that are sharp, sturdy and cut to prevent grooving and running the file off the work. The Brass file has a short upcut angle and a fine long angle o ver – cut which produces small scallops to break up filings and enable the file to clear. With pressure, the sharp high-cut teeth bite deep, with less pressure, the short upcut angle smoothes.

Filing plastics

Hard plastics are dense and brittle, and material is removed as light powder. The abrasiveness of hard plastics requires files with high sharp teeth. Soft plastics are filed in shreds so Shear Tooth files should be used for this application. 

Filing soft materials

Soft materials such as Aluminum, Brass, Copper, Plastics hard rubber and Wood, a Shear Tooth file provides fast material removal with good smoothing qualities. The combination of the Single Cut and the Long Angle helps the Shear Tooth file to clear. Because of the Long Angle, the file has a tendency to run to the left on narrow surfaces. This can be overcome by filing with a diagonal stroke to the right.

Precision filing

For filing such as that employed by the instrument industry, there is a range of Swiss Pattern files. The delicate precision work calls for these files be made to exacting measurements and finer cuts. The flat Precision file should be used with a slow smooth stroke moving the file laterally along the work on the forward stroke. In using Round or Half Round types, the filing should be clockwise to ensure a deeper cut and a smoother finish.


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