(fig. 57). In case the surface of a piece of wood should not be smooth enough, even after the jack plane and trying-plane have been used, the smoothing plane is resorted to.

In very fine work it is always necessary to use the smoothing plane to finish, for it is not possible to press down the longer jack and trying planes sufficiently tight to get smooth surfaces. They are, moreover, not so finely set, and have not such narrow mouths as the smoothing plane.

The latter, which is only 7 1/2 ins. to 8 ins. long, with 21/4-in. to 2 1/2-in. iron, can be pressed down, as might be imagined, much closer to the wood, the force not being spread over such a large area as in the larger planes. The sides of this plane are curved to assist in holding it. This is the more useful and essential, as there is no handle on top to hold.

The irons, wedge, and escapement are the same in principle as in the larger planes, but the iron is set invariably as finely as possible, with the cap very close to the edge, the shaving to be produced being as fine as silk.

Sometimes, to get additional accuracy and weight, smoothing planes are made with iron faces, and even wholly in iron. These faces are in two forms.

Fig. 57.

In one, the whole of the face consists of one plate, which is screwed on, the screws being countersunk, and the holes filled up level with the plate by running in molten metal.

In the other, only the portion in front of the mouth is of iron, and in this case it is held in position by a screw passing through the top, as in fig. 58.

There is a slot in the back of the iron face, as shown, which takes the flat end of the screw, and permits of the position of the iron being altered when it becomes necessary, by the unequal wearing of the iron and wooden portions of the face.

Fig. 58. - Showing an iron-faced smoothing plane, with elevation of screw bolt, plan of head and cap, and plan of iron face.

These planes are particularly useful in finishing up the surface of hard woods, and one should be found in every manual training class room.

Boys should use slightly smaller planes than men, the dimensions recommended being 6 1/2 ins. to 6 3/4 ins. long, with 2-in. iron.