This section is from the book "Spons' Mechanics' Own Book: A Manual For Handicraftsmen And Amateurs", by Edward Spon. Also available from Amazon: Spons' Mechanics' Own Book.
A scraper having a flat extremity is easily made of a small flat file, the thin taper portion of the file being first broken off, and a straight smooth extremity produced with grinding on a grindstone. The two broad sides are ground near the intended cutting edges, to destroy all convexity in that part, and to produce a slight concavity, for giving a cutting property to the edges, these two concave sides being afterwards polished with flour-emery cloth. The flat extremity requires to bo slightly curved and convex, and is ground until about a sixteenth of an inch prominent in the middle. After such a scraper has been properly made, the several grindings for sharpening are entirely performed upon the flat extremity, so named, the broad sides not being ground, but merely rubbed on an oilstone. An oilstone is also required to smoothly polish the cutting part every time the tool is sharpened.
Three-cornered scrapers are much used, and are made of triangular files of various sizes; the points of these are ground on a grindstone until the three intended cutting edges are regularly curved and convex; and the tool is finally polished on an oilstone. Scrapers having broad thin ends for scraping sides of holes, concave surfaces, brasses, shells of steam-cocks, and similar work, require a concave side, that may be termed the bottom. This side or surface is that which bears on the surface being scraped, and, through being concave, the tool has a superior cutting property, and is also easily moved to and fro by the operator without being liable to rock or cant while on the work.
A mode of making a scraper very light, to promote an easy handling, consists in thinning the intermediate portion, thus making it much thinner than the cutting part. If a scraper thus lightened is not thick enough to permit its being firmly held by the workman, the thin portion is covered with a few layers of cloth, flannel, worsted, felt, or similar substance, to enlarge the mid-part of the tool to a convenient thickness. Such a covering is also useful for all scrapers, whether thick or thin, rectangular or triangular, if they are small, to avoid cramping the fingers.
Scrapers that are made of files by grinding need no hardening; but if one has been forged by thinning and spreading one end of a piece of round steel, the process of hardening is performed after the tool is roughly filed to its shape. For scrapers, no tempering is necessary.