What are files?

Files are tools in the domain of mechanical engineering that are used in mechanical workshop applications. Files are the multipoint cutting tool that removes materials from a workplace. Files help to get the material to the failure point when there is a relative motion between them and the material. A file helps to cut, trim, reduce dimensions and provide surface finish to the material. The material is removed in the form of fine particles from the parent material.
Files are primarily manually operated and are rarely implemented on machines. Material compatibility of files ranges from hard and soft metals to woods and plastics.

File terminology

Files are made up of case hardened steels having their cutting edges arranged in certain patterns. The basic parts of a typical file are outlined below.

Tang

Tang is the shallow protrusion or the pointed end on which a wooden handle is attached. Some files have wider tangs that do not require an external handle to be mounted on.

Heel

The heel is the neck of the file from where the main body of the file begins.

Belly or face

The cutting activity of the file happens at the belly or face of the file. This face has multiple cutting edges that are arranged at specific patterns. The amount of material removal depends on the area and length of the belly or face of the file. The belly or face of a file can be selected as a single cut or double cut based on the suitability of applications.

File edge

The edge of the file can involve cutting action depending upon the presence of cutting edges. Some files are provided with smooth edges while some files are provided with cutting edges. Depending on the file body profile, some files can have flat, tapered, and round edges.

Point

Unlike the name, the point is the top edge of the file where the cutting edges end. The tip of the point to the base of the heel represents the length of the file.

Cutting edge patterns of files

There are two types of patterns based on which the cutting edges of a file are arranged. They are outlined below.

Swiss pattern

Swiss pattern files are usually smaller in size than the American pattern files, also they provide finer cuts. These files are usually 3 inches to 6 inches long and have coarseness values measured as 0, 2, 4, and 6. The zero is the file with the highest coarseness and 6 being the finest.
These files have cutting teeth that extend to the edge of the file, to provide easy trimming and cutting of internal areas of components with circular cross-sections. These files also have narrow points which make it suitable to remove materials from tighter areas and perform precision cuts.

American pattern

American pattern files are large-sized files and usually have uniform cutting patterns. These are files are mainly used for operations like deburring, shaping, and finishing operations. Due to their large sizes, these files are used for fast and controlled removal of materials in engineering applications. The material removal rate (MMR) for such files is high.
These files are available in three grades of cut; smooth cut, second cut, and bastard cut. The length of the file signifies the degree of coarseness of the file. For instance, a 10-inch bastard cut file is finer than a 16-inch bastard cut file.

Different types of files

Based on the type of pattern a file uses, there are different types of files. Some of the few and important types are explained below.

American pattern

Based on the American pattern, there are three files types.

(1) Machinist's file These files are specially designed for various hard and soft metals. These files are characterized by their cutting edges present on both sides of the body, due to which it is suitable for faster material removal.

(2) Saw sharpening files These files are primarily intended for sharpening, dressing tool cutting edges, and cutting teeth of saws. These files have single cutting edges that provide finer cuts to the materials.

(3) Special-purpose files These files are developed to perform certain specific operations. The files in this category involve wood rasps, foam files, and body fillers. These files also have different body shapes that allow users to use them for specific applications.

Swiss pattern

The files in this category have three different types:

(1) Die-sinker files These files are specially designed to shape and finish dies of different mechanical applications. They are generally smaller versions of machinist files with smaller tangs. These files come in sets with different body geometries meant for different applications.

(2) Die-sinker rifflers These files have narrow points which makes them suitable fine detail works. These files are characterized by uncut middle sections.

(3) Needle files These files are used by jewelers, die makers, and detailing craftsmen. These files come in twelve different shapes and are characterized by knurled handles. Some files have inbuilt plastic handles for the comfort of the user.

Filing techniques

The method of filing is not simply a reciprocating relative motion, a correct filing technique will result in faster material removal with a smooth and accurate finish. There are three filing techniques widely used in industries and various works person, they are outlined below.

Straight filing

Straight filing is the movement of the file along the length of the workpiece, holding the file either straight or slightly oblique. This kind of filing is characterized by push and return stroke maintaining downward pressure. The material is removed during the pushing stroke

Draw filing

It is a filing technique that provides material removal during the return stroke. In this technique, the user holds the file at the point and the tang and does a pulling stroke towards himself, maintaining a uniform pressure with the workpiece. This method provides a smoother surface finish.

Lathe filing

This technique smoothens workpieces that are being turned on a lathe machine. The is file is held at a constant position on the workpiece which is rotated continuously on the lathe. This technique provides a quick and larger material removal in a short amount of time.

Context and Applications

This topic finds its existence in various undergraduate and postgraduate degree courses like

• Bachelors of Technology (Mechanical engineering)
• Bachelors of Technology (Civil engineering)

Practice Problems

1. Which of the following file patterns provides a fine finish?
a. American pattern
b. Single cut pattern
c. Swiss pattern
d. Both a and b

Answer: Option c
Explanation: The Swiss pattern files are smaller as compared to the American pattern and provide a fine finish to the workpiece.

2. Which of the following filing technique removes material during the push stroke?
a. Draw filing
b. Straight filing
c. Lathe filing
d. None of above

Answer: Option b
Explanation: The straight filing technique removes material during the push stroke.

3. Which of the following filing technique remove material when the file is pulled towards the user?
a. Draw filing technique
b. Straight filing technique
c. Lathe filing technique
d. All of these

Answer: Option a
Explanation: The draw filing technique removes the material from the workpiece when the file is pulled towards the user.

4. If the grade of the file reads 6, which of the following is true for a Swiss pattern file?
a. The cutting edge is highly coarse.
b. The coarseness of the cutting edge is medium.
c. The cutting edge is very fine.
d. The cutting edge is intermediate between coarse and fine.

Answer: Option 3
Explanation: A Swiss pattern file having grade 6 signifies a fine cut

5.  Which of the file is used by die makers, detail craftsmen, and jewelers?
a. Die-sinker rifflers
b. Die-sinker files
c. Needle files
d. Machinist's files

Answer: Option c
Explanation: Needles files are used by die makers, detail craftsmen, and jewelers.