Rasps and Files
Files originated in Egypt and have been used since the Bronze Age. Traditionally they were hand made. A file-making machine was designed by Leonardo da Vinci, but the first one was not built until 1750, and machine file-making was not established until a century later.
Files are used to smooth metal and wood, to remove burrs and local irregularities, to enlarge and finish holes and slots, to sharpen cutting tools and, with a saw set, to set saw teeth.
They are classified by their cut (how the teeth are arranged on the blade) and the degree of coarseness. This is determined by the number of teeth per inch and the amount of space between the rows of teeth. In general, the longer the file the coarser it is.
Some files have one edge un-cut. This is called the "safe" edge, and can be rested against an inside work surface without damage while the other edge or edges do the filing.
Few files have handles. Handles, usually of softwood or composition, are sold separately. One handle usually fits a small range of files.
Never use a file without a handle, as the tang can be very dangerous.
Fitting the handle
Insert the tang into the handle socket. Tap the handle on the workbench until the tang is seated. Never use a hammer. Tap lightly with a mallet if the handle is difficult to get on. To remove the handle, pull it from the file while tapping the ferrule gently on the edge of the workbench.
Break in new files on brass, bronze or smooth cast iron. When they have become rough on that they are ready for heavy work on hard metals. Never start a new file on work narrower than the blade. Wood files need no breaking-in.
Files are single cut, double cut or curved tooth. Single cut files have parallel rows of teeth cut at an angle of 60° to 80° to the edge. Double cut teeth have a second set of parallel grooves cut into them, usually at an angle of 45°. The cut of the file determines its use. A single cut is used for precision work and a double cut for fast preliminary
Use curved tooth files (top) on soft metal, single cut (centre) for fine work and double cut (bottom) for roughing.
Clean files frequently and hang them in racks if you use them often or wrapped up individually if stored for a long time. Do not use them to pry things open or to strike objects as they are very brittle and break easily.
Whether a file is rough or smooth depends on the number of teeth per in. and the space left between each row of teeth.
There are three generally accepted degrees of coarseness:
1. Bastard, medium coarse with 26 teeth per in.;
2. Second cut, medium smooth with 36 teeth per in.;
3. Smooth, with 60 teeth per in.
Some makers also provide rough and dead smooth files.
Cuts and coarseness
Files are available in many combinations of cut and coarseness. The most popular are shown above.
Using a file
Filing is harder than it looks, and you may need to practice on scrap or unimportant pieces before you perfect your skill. Always clamp the work, however small, in a vise, preferably at elbow level. Set it low in the vise to prevent vibration and allow the work to project slightly. Clamp large sheets to the workbench.
Never use a file without a handle. Remember that the file cuts on the forward stroke only so apply even pressure as you push the file across the work, and lift it on the return stroke. Hold the file as shown and try to keep it in a straight line. Chalk applied to the teeth of the file helps to keep them clear of any metal residue.
Hold the handle of the file in one hand and the tip of the file with the other. File in a straight line across the work, introducing the file at 30J to the vise jaws.
With large flat areas, avoid a curved surface by constantly changing the direction of the file, though not the angle of approach. Check frequently with a square edge that you are filing true. It is very easy to establish a faulty stroke.
If the work is becoming curved, you are starting the stroke too early and finishing it too late. If there is a hollow, you are starting the stroke too late and finishing it too early.
Filing round stock
When filing round stock, the ability to rock the file is an advantage, unlike filing flat work. The file must be constantly angled so that all the teeth come into contact with the work. This keeps the file even on the workpiece.
Draw filing puts a smooth finish on a piece, removing all cross filing marks. Use a single cut file, make sure it is clean and well chalked. Draw the file across the woik toward you. For a fine finish wrap the blade in emery cloth. Do not overdo draw filing as you could unintentionally hollow die surface of the work. Use a flat file on fiat surfaces and outside curves and a round or half round file for inside curves.
Hold the file at right angles to the work, using two hands close together to prevent snapping. Light pressure is needed for light work, heavy for rough work. You may have to use the palm of your hand rather than the fingers to guide the file over coarse material. Do not use your body weight for extra power. The file will break.
Use a single cut file to remove burrs. Clamp the work in a vise, or to the workbench if it is large. For small areas of local burring, file across the edge.
Filing long burrs
To remove a length of burr or to chamfer an edge, angle the file and push it along the length of the edge.
Files need to be cleaned regularly otherwise they become "pinned", or clogged with filings. Pinned files slip on and scratch the work and quickly become unusable. Clean them with a file brush or file card. The file brush has two brushes, one coarse and one fine, and incorporates a wire pick to remove stubborn bits of filing. A file card has a coarse brush and a wire scorer on the back for extracting individual filings.
When the file is clean, chalk it before you use it again. Never oil a file or strike it to remove excess filings.
Using the file brush
Stroke the file brush parallel to the file teeth. Remove obstinate filings with a nail or ice pick and soft metal residue with a block of end grain hardwood.
Chalking the file
After cleaning the file, chalk it before use. This fills up the gaps between the file teeth, discouraging further pinning. Make sure that the gaps are well packed with chalk.
SIZE:4 to 18in.
USE: To file flat surfaces
The commonest file for all types of work except inside curves, the flat file tapers in both width and thickness toward the head. Single cut and double cut flat files are available, but the most general type is the double cut bastard.
SIZE: 4 to 20in.
USE: To file round holes or in curved surfaces
The round file tapers toward the point and is used to enlarge or smooth round openings and to finish concave surfaces. Small versions of the round file are sometimes called rat-tail files. Use the round file on small circular openings; the half round file is best for larger round areas.
Half Round File
SIZE: 4 to 18in.
USE: All purpose filing
The half round file is the most useful of all the files, combining the features of both round and flat files. One side is rounded and one flat, so the tool can be used on flat, concave and convex surfaces. It also files both wood and metal. Use it for work on larger circular areas.
SIZE: 4 to 18in.
USE: General purpose filing
The hand file is slightly different from other files. It is flat in cross section but has parallel sides right up to the tip, tapering only in thickness. There is one safe and one "live" edge, and it is consequently useful for stepped work, and any general jobs where a safe edge is needed or where both sides of a corner must not be cut simultaneously. "Hand" is possibly a corruption of "handy".
SIZE: 3 to 8in.
USE: To file narrow openings
The pillar file is a slimmer version of the hand file, with one safe edge. It is mostly used for slots and keyways. Narrow pillar files, about half the width of the standard variety, are used for very small orifices.
SIZE: 4 to 20in.
USE: To file square holes or angles
The square file is used on rectangular slots, keyways and splines. Some models have three sides toothed and the fourth left "safe"; in a confined space the file can rest on its safe edge without damaging its surroundings, while the other edges do the work.
OTHER NAME: Three square file
SIZE: 4 to 18in.
USE: To file angular stock
The triangular file has three flat sides. It is used to file acute internal angles, clean cut square corners, enlarge and clean up angular holes and sharpen serrated jaws and saw teeth.
OTHER NAME: Mill saw file
SIZE: 8 to 10in.
USE: Fine work and sharpening
Mill files can have one or two rounded edges and often have one safe edge. They are always single cut, and are mostly used for lathe work and draw filing, but are basically all-purpose fine finishing tools. They are also used to sharpen mill and circular saws, knives, lawn mower blades, axes and shears.
OTHER NAMES: Swiss pattern files, jeweler's files
SIZE: Length: 3 to 12in.; Teeth per in.: 34 to 184
USE: Precision filing
These small, delicafe files are usually sold in sets. They are very accurately made, and the tangs are knurled and lengthened to make handles.
Needle files are principally used for precision work on instruments or mechanisms, but they also make fine finishing tools on important work. They are also used to sharpen the fragile spurs on spur nosed drill bits and can be used to tidy up slots, square corners, notches, key-ways and grooves.
Sharpening the spur
Hold the twist of the bit firmly against the bench, tip uppermost. File inside the spur with a flat needle file. Filing outside will reduce clearance.
Sharpening the cutter
Rest the bit on the bench, lead screw down. Work a triangular needle file through the throat of the bit, filing the cutters on the underside only.
Sharpening the side wings
Hold the bit as for sharpening the cutters. Using a square needle file, file the side wings on the inside only.
SIZE: 4 to 8in.
USE: To file very acute angles
The knife file has a section like a knife blade, and tapers toward its point. It is used by tool and diemakers on work which has acute angles.
SIZE: 4 to 8in.
USE: To file locks and keys
The rectangular warding file is a small slender file, tapering to a narrow point. It is primarily a locksmith's tool, used for filing notches on keys and locks, but can be used where a thicker file would be too clumsy. It has a broad, strong blade, so can be used vigorously on edge.
SIZE: 3 to 10in.
USE: To file saw teeth
Various files are made specifically to file the teeth of the many models of saw on the market. There are taper saw files, mill saw files with two square edges, double ended saw files, cross cut saw files and chain saw files. Ail are available in coarse or fine grades. Use them with a saw set to keep saw teeth sharp. Otherwise use a mill file of the correct cut.
There is also a tool on the market called a saw sharpener, which will accurately sharpen cross cut, tenon and fleam saws when used with a saw set. It is a small double ended file.
Unlike file teeth, rasp teeth are formed individually to slice off slivers of wood quickly and easily. Rasps are mostly used on wood, but work well on soft metal (aluminum, lead), leather and bone as well. Bastard (coarse) and smooth cut are available, and the usual shapes are flat, round and half round.
Surform Round File
MATERIAL: Blade: steel; Handle: plastic; Body: aluminum
USE: To enlarge holes and shape decorative cuts
Surform tools are unique. They are hollow rasps, consisting of steel blades perforated with sharp edged holes which cut away wood rapidly. The waste is passed easily through the holes.
The round file is tube shaped and has a removable front holding piece. It can do any round file work on wood, aluminum, copper, plastics, tiles, laminated surfaces and metal no harder than mild steel. It is particularly useful for enlarging holes.
Surform Flat File
MATERIAL: Blade: steel; Body: aluminum; Handle: plastic
USE: General filing
The surform flat file has the same perforated blade as the round file, and does the same job as a standard fiat rasp.
SIZE: 8 to 12in.
USE: To remove wood quickly
Cabinet rasps are the best known wood rasps. They are usually shaped like half round files with one flat and one rounded edge. There are also flat versions. Cabinet makers use them to rough file wood before finishing with a wood file or abrasive paper.
SIZE: 8 to 14in.
USE: To finish wood
Used for wood only, the wood file is used after a rasp to smooth wooden surfaces. It has coarse file teeth.
Flat Wood Rasp
SIZE: 8 to 16in.
USE: General rasping
This is exactly like a flat file in section, but is rasp cut. It can be used on flat or convex surfaces.
Round Wood Rasp
SIZE: 6 to 14in.
USE: To rasp round holes or curved surfaces
This is a large, round sectioned rasp, which is used on tightly curved wood sections or circular holes. Bastard, second cut and smooth grades are available.
Half Round Wood Rasp
SIZE: 6 to 16in.
USE: General rasping
The half round rasp, like the half round file can be used on flat, concave and convex surfaces. Bastard, second cut and smooth grades are available. There is not much difference between this tool and the half round cabinet rasp.
OTHER NAMES: Last maker's rasp; shoemaker's rasp; 4-in-hand rasp file
SIZE: 8 to 14in.
USE: To file or rasp
This is a versatile, double ended tool. One end has a file cut surface on each side and the other end is rasp cut. Use it on wood or leather.
SIZE: 12 to 18in.
USE: Rough wood filing
The horse rasp is the biggest and coarsest rasp there is. It is used for rough work, and normally has no tang to take a handle but is squared off at each end. Tanged versions are available up to 16in.
OTHER NAMES: Woodcarver's file; woodcarver's rasp; bent rifliers
SIZE: 6 to lOin. MATERIAL: Handle: hardwood; Blade: steel
USE: To file woodcarving
Rifflers are craftsmen's tools. They are miniature files, with the same selection of cut, coarseness and cross section, and are adapted to suit individual needs. Some are double ended, with rasp cut blades at one end and file cut at the other. Some are ready fitted with hardwood handles, and are bent at an angle of 45 to reach into the hard-to-get-at places on a woodcarving or sculpture. Diemakers have a special set of rifflers which are more substantial than wond-carving rifflers.
Rotary Files and Rasps
SIZE: Shank diameter:1/8 to 1/4in.
USE: To shape and file small areas
These tools are sold singly as well as in sets. The rotary files have finer teeth and cau be used on both metal and wood. The coarser rasps should only be used on wood. These files and rasps come in a huge variety of shapes, cut in bastard, second cut and smooth grades. They are mounted on shanks and are used with a power driven flexible shaft tool. Some can fit the chuck of an electric drill.
These tiny, accurate files are particularly useful for modeling work or intricate carving. They can be fitted to the miniature power drill. The best tools for carving are called burrs.
Rotary file shapes
These are just some of the large selection of shapes available to the woodcarver or sculptor.
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