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What is a file’s cross-section?

What is a file’s cross section?

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Diagram of the cross section of a triangular file, such as a taper saw file or a three square file The cross section of a file is the shape you would get if you cut the file in half widthways. For brevity, the word ‘section’ is sometimes used to mean the same thing.

What are the different cross sections for files?

Illustration of rectangular and triangular cross sections, which are the most common for files Files are produced in a variety of different cross-sectional shapes. The most common sections are rectangles and triangles.
Image to show files with rectangular and triangular cross-sectional shapes in use This is because rectangular files are extremely versatile and can be used for a wide range of different applications, and triangular files are excellent sharpening tools.
Examples of different file cross sections Other cross-sectional shapes include circular, semi-circular, oval, tear drop, square and rhomboid (diamond-shaped).

Why are there differently shaped files?

Image of a DIYer using a half round file to create a curved groove The cross-sectional shapes of each of these files lend themselves well to a different set of tasks. For example, half round files, with their semi-circular section, are ideal for filing inside pipes, creating semi-circular grooves and finishing concave and convex surfaces.
A DIYer sharpening a chainsaw with a file In addition, sharpening, shaping and finishing tasks each have their own requirements when it comes to cross section.
A DIYer lining their file up so that they can work at a shallow angle to sharpen it


In order to sharpen a bladed tool, the file that you use has to fit that blade’s shape. In many cases, this will be flat, which opens the door for the use of a wide range of files.

A selection of veneer knives, which can be sharpened with a veneer knife file However, in the cases of saws and some blades that attach to machinery, there will be gaps of a specific shape into which the file must fit. In this case, the cross-sectional shape of the file is vital, as any discrepancy will cause irregularities during the sharpening process that could ruin the tool instead of rejuvenating it.
Image of a triangular hand saw file showing outline and cut Saws, in particular, quite often require triangular files with specific angles for accurate sharpening, and there are a number of files that have been designed specifically to sharpen just one tool.
Image of a cross cut file showing cut and outline For example, crosscut files are designed to fit the 60° angle between the teeth of a crosscut saw, as well as deepening the circular gullets found at regular intervals along the blade.

For more information, see: What are saw files?and the saw files section of this guide, which begins with What is a mill file?and concludes with What is an auger bit file?

Image of a DIYer filing a convex surface with a flat file

Shaping and finishing

When you are shaping a piece of material using a file, the cross section defines the way in which material will be removed. In many cases, this will either result in you using one face of the file, in which case it’s the shape of that single face that matters.

Image of a DIYer using a three square file to smooth the inside of a shape cut into a thin piece of wood In other cases, you may be using the edge of a file, which means you can get a completely different shape from the same tool.
Image of a triangular groove illustrating a use for lozenge files and slitting files In either case you can work out which shape of file you should use by matching it to the shape you are trying to create in your piece of material.
Image of a DIYer filing a hole in a door with a round file When finishing a pre-cut or pre-filed workpiece, this works in the same way. If you match the shape of your file to the shape of the surface or corner that you will be finishing, you can’t go wrong.
Image of a right angled notch that has been cut by a square file For example, if you are filing a triangular notch with a 90° angle, a square file would be a suitable choice.

For more information, see: What are machinist’s files?and the machinist’s files section of this guide, which begins with What are hand and flat files?and concludes with What are needle and escapement files?

Are different files interchangeable?

A DIYer using a flat file to shape a piece of metal for stamping In terms of cross section, the most important part of a file during any single application is the one that is in contact with the workpiece.
A DIYer using the flat side of a half round file to deburr a piece of copper For example, if you are filing a flat surface, you will most likely be using a flat, hand or mill file. However, you could substitute in a number of other files that also have at least one flat face, including half round, taper saw, slitting and warding files.

For more information, see: What are half round, ring and marking files?What are taper end and double ended saw files?What are sitting and slotting files?and What are warding files?

Image of a V-shaped groove being created by a knife file Similarly, substitutions may be possible when using the edge of a file to create a groove. For example, the ‘blade’ of a knife file is a very similar shape to the narrow, triangular section of a pippin file. As such, you may be able to use a pippin file to do the same job as a knife file would have.

For more information on knife and pippin files, see: What are knife, pippin and auriform files?

Image to show that American pattern second cut and Swiss pattern 0 are the same If you are making a substitution in this way then it’s also important to make sure that the new file has the same type of cut and coarseness as the one you would have been using.

For more information, see: What is a file’s cut?What is a file’s coarseness?and the individual file guides.

Information for specific files

Wonkee Donkee reading a DIY guide on the uses of specific files As there are so many different types of file, and cross section is not the only characteristic that defines a file’s ideal applications, more specific information on the way that a file’s section influences its uses can be found in the individual file guides.

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