Diamond files are used for filing extremely hard materials such as hardened steel.
What are the characteristics of diamond files?
Cross section and taper
Diamond files can be found in many of the same shapes as the other files listed in this guide.
Cut
Diamond files are not cut with teeth in the same way as rasps or files.
Instead, they have pieces of diamond or tungsten carbide grit embedded in the cutting faces of the tools.
Diamond is much harder than tool steel and therefore makes for a much more effective abrasive tool.
This is the reason why diamond files are effective on tool steel. They can also be used to file brittle materials that would crack or break if a conventional file was used. These materials include ceramic, glass, and some plastics.
For more information on why diamond can abrade steel, see: What is hardness?
Swiss or American?
Diamond files use a completely different system for measuring coarseness than American and Swiss pattern files.
You will find them listed as having a certain ‘grit’ number, for example ‘325 grit’. The lower the grit number, the coarser the file.
What is grit?
The term ‘grit’ refers to the number of sharp particles per square inch, so an 800 grit tool would have 800 grains of diamond concentrated into quite a small area.
If you had an 800 grit diamond file with a cutting area of just 4 square inches, that would be more diamonds than there are in the crown jewels!