Abrasives
These are principally used for polishing, but are also needed for working such hard stones as jade, and for drilling unusually hard substances such as glass and porcelain.
Carborundum and emery are both abrasives of great hardness, and they are ordinarily used in conjunction with a soft iron drill or a revolving iron disc. The cutting edge is charged with the abrasive mixed with a little water.
For polishing surfaces it is necessary to start with a comparatively coarse grade, replacing it with a finer grade or substance as the work progresses. Pumice powder, putty powder, tripoli, whiting, and jeweller's rouge are all fine abrasives.
Emery-paper, emery-cloth and glass-paper are convenient ways of using abrasives, and they can be obtained in a number of grades, ranging from very fine to coarse, for various kinds of work.
See Hardness of Materials; Polishes and Polishing.