Inexperienced workers, especially children in schools, sometimes rush and try to bypass the planing operation that is used to remove rough edges, including planing machine marks in the case of veneered wood. Sometimes attempts are made to scrape a surface with a hand scraper instead of using a brush or scraper.
The hand scraper often follows the irregularities or undulations of the board and does not level the surface at all. Attempts to smooth a machine-planned surface with sandpaper alone are always time-consuming and unsuccessful. The sandpaper follows the ripples made by the cutting machine and does not properly smooth or level the surface. Such impractical procedural methods mark a person as a novice with little knowledge or experience.
Scrapers, when sharpened and used correctly, are a great source of satisfaction for forestry workers and suppliers, doing work that often surprises an amateur. In workshops where a sanding machine is not available to smooth and level wooden surfaces, scrapers are very important tools.
There are two different types of scrapers, one of which is the flat scraper. Scrapers are tools that hold cabinet scrapers or scrapers into cylinder heads, which in some of their forms resemble aircraft cylinder heads. Stanley Nos. 12, 112 and 80 are examples of scrapers or holders which are very satisfactory. Scraper blades for use on supports or scraper planes are generally ground with a beveled edge rather than a square edge.
The procedure for sharpening a scraper plane is as follows:
o Remove the old hook by sharpening the blade, which you should hold with the flat part on the stone. Never use a file for this purpose, as the side of the blade will be scratched and these scratches will gouge the new hook.
o File a bevel in the blade at about a 30° angle, using a 10″ or 12″ milling file. Lace up the corners slightly, as you would when grinding a flat bit. The bevel can be ground on a grinder if convenient.
o Grind the edge very carefully on an oil stone. Any warped edges can be removed by cutting a piece of wood, using the blade as a chisel, but drawing the edge across the grains of the piece as with a knife. Repeat this operation until the blade is sharp and the feathered edge is removed. Usually it is not possible to get as sharp and smooth an edge on a scraper blade as on a flat bit. Finish the sharpening process by using a belt as in sharpening a flat bit.
o Place the doctor blade in a vice, or preferably in a special clamp or kit made for that purpose. Take a large grinder made of specially hardened steel and twist a hook into the edge of the bezel, bending the metal to the flat or front side. Use about five strokes, turning the hook further each time and holding the burnisher at about a 95° to 100° angle to the face of the blade on the last stroke.
A sharp doctor blade as described above, if properly adjusted with appropriate measuring tools in the plane of the doctor, will cut long, thin chips and plane against the grain to some extent without breaking the fibers. A scraper brush will make a much smoother surface on most woods than a smooth surface.
plane.
On some very hard, crooked, and grained woods, the smooth rail should not be used. You must use the scraper brush throughout the planing process to avoid removing fragments such as flakes on oak and eyes on bird’s eye maple.
A dull rasp blade hook can sometimes be partially flattened with a burnisher and then turned as in the first hook turn.