There is a wide variety of files and rasps available on the market. These tools are available in just about any hardware or home improvement store, or online. Regardless of the project you are working on, there is a file or rasp that is appropriate for it. While many people use the terms interchangeably, files and rasps differ in function and purpose. Files have ridges that are in evenly spaced, parallel rows that run on the diagonal. Rasps on the other hand, have teeth that are more randomly spaced, which makes a rasp inherently more efficient, but also more course, when removing whatever is being worked on. Files and rasps are used in between the sawing, cutting, or sanding phases of working with a material. They can be used to remove rough edges or to further shape metal, wood, ceramic, glass, fiberglass, epoxy, and any number of other materials. The three primary uses are on metal, wood, and ceramic and glass.
Wood Files and Rasps
Wood files and rasps are generally referred to as medium or cabinet files or rasps. This is referring to the coarseness of the grit on the tool and they are ideal for wood working projects. A rasp can be used to eliminate rough edges after cutting the wood, and a file to smooth out any grooves or ridges that are created by the first two steps. These tools come in a variety of shapes and sizes, but generally an eight or ten inch file and rasp are a good size to use in working with wood projects.
Metal Files and Rasps
A file or rasp can be used to debur cut metal, smooth edges, and refine joins. Files and rasps that are meant to be used on metal are generally rougher or more course than wood tools. You will want to match the size of the project and type of the material to the appropriate file or rasp. Smaller tools are for smaller, more delicate projects, and conversely, larger, rougher tools are meant for larger projects and courser grade materials.
Ceramic and Glass Files and Rasps
Rasps that are used on glass or ceramic are generally finer toothed, smaller tools than those that are used on wood or metal. Because of the delicate nature of these materials, slow, exacting progress is what is needed which is difficult to achieve with larger tools that it is smaller ones. Rasps can be used to take the majority of an edge off a piece of ceramic material (once it's fired), and the file can be used to smooth it. You will frequently find this necessary on a piece of fired pottery or an imperfectly cut piece of glass. Four and six inch tools are best for this type of work. Care needs to be taken to have complete control over the tool, and so a handle on the tang is imperative.