The methods of fitting the guideways and guides of planer beds and tables is given in the examples of erecting.
Fig. 1605.
A very good method of testing them, however, is as follows:—Suppose that we have in [Fig. 1605] a plate that has been planed on both edges g, h, and that in consequence of a want of truth in the planer guideways edge g is rounding and edge h hollow, the plate being supposed to lie upon the planer table in the position in which it was planed.
Fig. 1606.
Now, suppose that it be turned over on the planer, as in [Fig. 1606], the rounding edge, instead of standing on the right-hand side of the planer table, will stand on the left-hand side, so that if that edge were planed again in its new position it would be made hollow instead of rounding in its length. It is obvious, therefore, that if a planed edge shows true when turned over on the planer table, the Vs of the planer are true, inasmuch as the table moves in a straight line in one direction, which is that affecting the truth of all surfaces of the work that are not parallel to the cross feed of the tool, or, what is the same thing, parallel to the surface of the planer table.
Planing Machine Tables.—In order that the guides on the table of a planer may not unduly wear, it is essential that they be kept well lubricated, which is a difficult matter when the table takes short strokes and has work upon it that takes a long time to perform, in which case it is necessary to stop the planing operations and run the work back so as to expose the guideways in the bed, so that they may be cleaned and oiled.