Where several parts are to be fitted together, the faces are turned in; in this case, the best surfaces should not be selected for faces. [Chapter VII], [section 75].
Fig. 57.
Fig. 58.
Before beginning to plane hold the piece toward the light, close one eye and sight as in [Fig. 57]. If the surface is not warped or in wind, the back arris ab will appear directly behind the front arris cd. Also sight the arrises for straightness, [Fig. 58], being careful to hold so as to get the full benefit of the light. Again, test from arris to arris, [Fig. 59]. The try-square may be used either side up, but the beam must not be held against either edge. It is not for squareness but for straightness that this test is made.
Fig. 59.
Notice the direction of the grain and place the piece so as not to plane against it. In [Fig. 60] plane from A toward B or the surface will be roughened instead of smoothed. When the stock is rough, the direction of the grain cannot be told readily. A few strokes of the plane will give the desired information. As most stock is to be planed to size, it is well to test with the rule before beginning to plane, so as to know just how much margin has been allowed. If you find you cannot true this first surface without getting the piece within one-sixteenth of an inch of the thickness required, ask your instructor to show you where the trouble lies.
