Abrasive tools are useful for shaping both hard and softwoods. Rasps and files come in a variety of sizes and patterns, for rough shaping and fine cutting. Rasps will cut wood and have fairly coarse teeth. Files have rows of finer teeth for wood, metal or plastics. Unlike planes and chisels, the advantage of rasps and files is that you can use them in any direction on wood, irrespective of grain, without the risk of fibres tearing or splintering.
Rasps will smooth out heavy, uneven surfaces quickly, and are powerful tools. Tools with hand-cut teeth are more expensive than machine-cut versions, but the results are better. Teeth are cut with a more random pattern, which mean fewer marks evident on the finished timber, which also tends to be smoother. The most popular type of rasp has a flat side and a half-round side, useful for shaping concave work.
The surform is a more advanced type of rasp with teeth punched from hardened steel plate. Holes in the teeth mean they are less likely to clog up than traditional rasps. Inexpensive and undoubtedly useful, surforms can be used on all sorts of materials, including plastics and non-ferrous metals. They are available in a variety of shapes and sizes, including straight and curved patterns. Blades are replaceable and require no adjustment.
Microplanes are a more recent development, with very efficient blades with razor-sharp teeth. These are interchangeable and make finer cuts than surforms, which tend to be rather coarse. Blades are relatively narrow and more delicate, so more care is needed when using them to prevent them flexing. Various blade patterns are available, from flat to V-groove to half-round.
•Keep files used for metal away from wood, and vice versa. If not, there is a risk of metal particles becoming embedded in the grain.
A rasp will leave a fairly rough surface, which can be made smoother using a file. A file is less aggressive and will smooth most of the marks made by the rasp. You should regard it as an intermediate step before applying abrasive paper. Teeth extend across the face of a file, unlike a rasp, which has individual teeth. Teeth patterns most suitable for woodworking are single-cut and double-cut. On a single-cut file, teeth extend diagonally across its face, producing a fine surface when cutting using a light touch. On a double-cut file teeth are still diagonal but run in both directions. This pattern cuts faster and produces a rougher surface.
Files are also graded according to the coarseness of cut: coarsest of all is the bastard cut; second cut gives a smoother finish; and smooth cut is the finest of all. You will need files for the odd metalworking task as well as for smoothing wood. Occasionally tool edges need softening or drill-bit shanks become burred. A rectangular single-cut mill file is ideal in these situations, and is a good all-rounder.
Files are often sold as blades without handles. It is important to fit handles to the tangs, however, as this makes these tools safer to use and will give you greater control when working with them. You can make or buy handles to fit.
Needle files are much smaller than conventional files, typically 152 mm (6 in) in length. Good-quality needle files can be used for precise cutting and cleaning up intricate edges that would be impossible to finish with other tools.
Unlike straight rasps and files, rifflers are S-shaped, with curved faces at either end. Those with coarse teeth have more of a ripping action, and although they can remove heavy bumps, you will still need to finish with finer rasps and files before you can do any work with abrasive paper.
CLEANING RASPS AND FILES
When used on some of the more oily or sappy timbers, such as teak or Scots pine, rasps, rifflers and flles have a tendency to clog up with sawdust. A wire brush will help here, or for the more stubborn blockages, a blowtorch. For cleaning files, use a piece of file card.
Word Discription :
Bastard cut File with coarse teeth for an aggressive cut.
Double-cut Teeth criss-cross in both directions across the file.
Second cut File with medium teeth.
Single-cut Teeth slope in one direction across the file.
Smooth cut File with fine teeth for the smoothest cut.
Tang The tapered end of a file or rasp, designed to be driven into a handle.