When a job cannot be finished accurately enough with a file, a tool called a scraper (Fig. 133) is used. Scrapers are generally made from octagonal steel flattened on both ends and tempered very hard to a light straw color. After grinding, the edge should be rubbed down on an oil stone. On one end of the scraper the edge may be slightly curved as shown.
Fig. 132. - File with Safe Edge.
Another type of scraper with a wood handle, sometimes called a graver, is used for work in lathes and for hand-work on round corners. A good scraper can be made from an old file. When work is to be scraped it must be first rubbed or tested on a standard and perfectly flat plate called a surface plate. The method used is to put a very thin coating of red lead mixed with oil on the surface plate. The high points which must be removed first, are shown by small red spots on the surface of the block. When the work is heavy and awkward to handle the surface plate may be rubbed on it. Care is required to rub over the whole plate evenly to prevent wearing and dishing the center.