In order to thoroughly exhaust this portion of our subject, several examples of detailed processes must now be given, in which the principles, implements, and machines mentioned will be applied to the planing of engine-work of various classes.

By reference to the hand-planing at page 207, it will be observed that bevelling of edges is practised previous to chipping an object; and a similar bevelling is sometimes effected for machine-planing. The particular cirumstances and conditions which render such treatment necessary are these: When a side of an object is to be roughly reduced to the required dimensions by removing one thick slice; in which case the bevelled edge is that at which the tool-point is liberated from the metal, and is at right-angles to the direction of the table's motion. Bevelling is also performed to remove hard edges and corners, such as the outer corners of cast-iron articles which become hard while cooling, and the sandy edges and corners of cast-iron and steel articles in general; in these cases, all the four edges of the side to be planed are bevelled. It is also necessary to bevel an object when it is especially necessary to prevent its hard flinty skin breaking or damaging a tool's edge at the moment it enters into contact with the object; bevelling for this purpose is performed upon one edge only, and this edge is that at which the tool enters the metal every time they meet each other.

Bevelling for machine-planing is effected either with rough filing, chiselling, or with a grindstone. Small hard iron and steel articles of only a few pounds each in weight are held in tongs and bevelled with a grindstone previous to fastening them to a planing-table. A large piece of work, which may have hard edges, is chipped after it is bolted to the table. When it is necessary to form very clean edges, previous to cutting off a very thin slice of any object, the bevelling is easily done with a file, which is applied to all the edges of the surface being planed.

It should also be mentioned here, that machine-planing of pieces having hard gritty surfaces is greatly facilitated by entirely removing the hard skin previous to planing, in addition to merely cleaning or bevelling the edges. Such preliminary cleansing of surfaces may be done either with old rough files, with a grindstone, with sulphuric acid and water, or with nitric acid and water; and if an article is allowed to lie in such a compound, it is said to be pickled. The particular mode by which a surface is cleansed depends on its size and shape. We now proceed to separately consider a number of details of processes as they are applied to the planing of ordinary portions of machinery.