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What are chequering and thread restoring files?

What are chequering and thread
restoring files?

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Image showing the chequered configuration of teeth on chequering and thread restoring files Chequering and thread restoring files are both characterised by their square teeth, although they are used for quite different purposes.
A gun handle with a section decorated by a chequering file Chequering files were designed to create chequered patterns on the handles of rifles and pistols. This is how the file earned its name.

For more information, see: How to chequer a gun handle with a hand file

A screw with damaged thread that will have to be repaired with a knife file Thread restoring files are used exclusively to clean up and restore damaged threads on bolts and screws.

What are the characteristics of chequering files?

Diagram of a rectangular cross section

Cross section

A chequering file (American spelling: ‘checkering’) is rectangular in cross section.

Image showing the outline and cut of a chequering file

Profile and cut

It is slightly tapered in thickness towards the point. It is cut on both faces, but safe on both edges.

Close up of the teeeth on a chequering file The cut on a chequering file is different to that of most other files. It is double cut, but the overcut runs parallel to the edges of the file, in vertical lines towards the tang. The upcut is at 90° to the overcut, making a square grid pattern on the file.
A serrated knife, best sharpened by a chequering file The grid-shaped teeth of chequering files, mounted on their flat, rectangular bodies, make them ideal for carving perfectly parallel grooves in wood or metal, or for jimping or serrating knife blades.
Image of jimping on a knife blade that has been created through the use of a chequering file ‘Jimping’ is the term used to describe the creation of notches on the back of the blade for improved grip.

For a step by step guide, see: How to jimp or serrate a knife

Flag of Switzerland - home of the Swiss pattern file invented by F. L. Grobet in the 19th Century

Swiss or American?

Chequering files are Swiss pattern files, although their coarseness is more often measured in teeth per inch than on the Swiss pattern scale.

What are the characteristics of a thread restoring file?

Image of differently sized thread restoring files

Cross section, profile and cut

A thread restoring file is blunt, has a square cross section, and is cut with a different coarseness of teeth on each of its working faces.

Image of a screw's thread to illlustrate the way thread restoring files are measured


The coarseness of thread restoring files is measured according to the number of threads per inch that the teeth will fit into.

Image to illustrate that neither the American nor the Swiss pattern grading systems apply to this file

Swiss or American?

As a result, they do not count as Swiss or American pattern files.

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