This section is from the book "Spons' Mechanics' Own Book: A Manual For Handicraftsmen And Amateurs", by Edward Spon. Also available from Amazon: Spons' Mechanics' Own Book.
After the wood has passed from the sawyer into the hands of the carpenter, the surface undergoes those operations which render it true and smooth These 3 planes do this work. The "jack," usually about 15 in. long, and the "trying" plane, ranging from 18 to 24 in. long, but, in exceptional cases, far exceeding these dimensions, are to external appearances alike; indeed, some regard the different handles as the only distinction between them, and that these handles show which must be used for rough work and which for smooth (see Fig. 355 as an example of the handle of a "jack-plane," and Fig. 356 as an example of "trying-plane" handle). This is an error. There are other differences, but the main and leading one is the different form given to the edge of the cutting iron.
If the iron of the "jack" plane be looked at from the front end of the plane, the form of the edge will be curved, as in Fig. 353; but the iron of the " trying " plane is straight, as in Fig. 354. Upon the curvature of the edge depends the efficient action of the "jack."
Sufficient has been said of the tendency of the fibre to draw the tool downwards; but it must not be forgotten that the same adhesion of fibre to fibre takes place between the surface fibres as amongst those below the surface. For the purpose of separating the surface connected fibres, the jack iron is convex. Note its action. The convex sharp edge is pushed along a horizontal plank, penetrating to a depth determined by the projection of each vertical section below the sole of the plane. The ends of this convex edge are actually within the box of the plane, consequently (sideways) all the fibres are separated by cutting, and are therefore smooth and not torn The effect of this upon the entire surface is to change the surface from the original section to a section irregularly corrugated. The surface after using the "jack" is ploughed, as it were, with a series of valleys and separating hillocks, the valleys being arcs from the convexity of the tool and the separating hillocks being the intersection of these arcs.
All traces of the tearing action of the saw have been removed, and from a roughened but level surface a change has been made to a smooth but in cross-section an undulating one.
The mechanician's next object is to remove these lines of separation between the valleys. For this the trying-plane is required. The trying-plane is longer than the jack, because the sole of the plane which is level is, so far as its size goes, the counterpart of that which the surface of the wood is to be; further, the trying-plane should be broader than the jack, because its object is to remove the hillocks and not to interfere with the wood below the bottoms of the valleys. If its action passes below the bottoms of the furrows, then occasion arises for cutting the side connection of the fibres, and however a workman may sharpen the edge of his trying-plane for this purpose, he in one respect has destroyed one object of the plane, because, so soon as the iron penetrates below the surface, then does the effect of the jack action begin to reappear, and the cutting edge should pass from the shape shown in Fig. 354 to the shape in Fig. 353. The result of the trying-plane following the jack is to remove all the elevations of wood above the valleys the jack left; and, secondly, to compensate by its great length for any want of lineal truth consequent upon the depth of bite of the jack.
Again, the mouth of the trying-plane is much narrower than that of the jack; hence the shavings removed are finer, therefore the slope of the iron, or its inclination to the wood may be less than is the iron of the "jack" - hence the line of cut is more nearly accordant with that of the fibre, and by so much the surface is left more smooth from the trying-plane than from the jack, as there is more cutting and less tearing action than in the jack. The reasoning hitherto pursued in reference to the purpose of this sequence of a jack and trying-plane might and does legitimately produce the conclusion that, after the trying-plane has done its duty, the work is as perfectly finished as it can be. Custom, and perhaps other considerations, have established that after the long trying-plane must follow the short and almost single-handed smoothing-plane (Fig. 357). So fur as the form of the iron of the smoothing-plane is concerned, there is no difference between it and the one used in the trying-plane; each (as across the plane) is straight, the corners being very slightly curved, but only so much as to ensure that they do not project below the line of the cutting edge.
It would seem that, whilst the trying-plane levelled down all the elevations left by the jack, and brought the surface of the wood as a counterpart to that of the plane, there might be in the fibre, or grain of the wood, twists, curls, and other irregularities which, whilst levelled, were yet left rough in consequence of the direction in which the cutting edge came upon them. Indeed, this cutting edge, in a long plane, which must advance in the direction of its length, must at times come across a large number of surfaces where the fibre is in opposite directions. The consequence is that there will be various degrees of smoothness; for good work these must be brought to uniformity. This is effected by passing a short-soled plane over the respective parts of the surface in such directions as observation may indicate. Hence the smoothing-plane is of use chiefly to compensate for such changes in the direction of the fibres of the wood as the greater length of the trying-plane could not conveniently deal with.
The plane shown in Fig. 355 is claimed to possess some advantages over the ordinary jack-plane, in that it gives a control over the thickness of the shaving and depth of the cut by the pressure of the hand, and prevents the drag of the bit on the board when the plane is drawn back. The stock of the plane is made in two parts, the upper portion A, which holds the bit, being pivoted to the lower part B at the rear end by a screw C passing through metallic guide plates D on each side the plane. The front end of the upper portion is raised from the lower portion by means of a spring E, which, when the pressure of the hand on the front of the plane is withdrawn, lifts the upper portion together with the bit or plane iron. The amount of this movement is governed by the thumb-screw F.
The "rabbet" or "rebate" plane, Fig. 358, differs from the preceding examples in that the cutter reaches to the edge of the wooden block, so as to enable the smoothing operation to be carried right into the corner of work. It is employed in making window frames and similar articles in which a recess (termed a "rebate" or "rabbet ") has to be cut for the insertion of some other material, as, for instance, a pane of glass. The cutter has not of necessity a square edge, but may be shaped like the examples shown in Figs. 359, 360, which are termed "skew," "round," and "hollow" rabbet-irons respectively.
Another form of simple plane is the "plough," intended for cutting a deep groove along the edge of a board for the purpose of inserting in it a corresponding "tongue" along the edge of another board to be joined to it. The tongue may be formed by using the rabbet-plane along each side of the board edge; but it is more convenient to employ "match" planes, which are made in pairs, one cutting the plough and the other the tongue. Their cutters are shown in Fig. 361.
The stop-chamfer plane, sold by Booth, Dublin, for 4s., is a very useful tool for cutting any chamfer from 1/8 in. to 1 1/2 in. with a constant angle and size. It is shown in Fig. 362. The box of the plane is made in much the same way as that of ordinary planes, and the iron is inserted and held in place in the same manner. The point of difference is that a A-shaped channel is cut along the sole of the plane, the sides of the channel being at right angles to one another, and at an angle of 45° with the sole of the plane; meeting in a point in a line drawn perpendicular to the sole, and exactly up the centre of the end of the plane. Thus the sides ac be of the groove are at right angles to each other, and at an angle of 45° to de, the sole of the plane, and they meet in c, a point in fg, which is perpendicular to de, and drawn exactly up the centre of the end of the plane, as shown.
The depth of the iron, which is indicated by the shaded part of the figure, is regulated to suit the width of the chamfer that it is proposed to make.
The preceding include all the kinds of plane in most general use; but it is obvious that the same principle may be applied to almost any form of cutter. Hence a great variety of tools, known as "moulding" and "filletstering" or "filister" planes, have been introduced, whose cutters consist of combinations of chisel and gouge edges. These are employed for cutting mouldings and beads of numerous designs, which are familiar to every one who has observed the edge of skirting boards in rooms, the panels of doors, or the sash-frames of windows. The great bulk of this class of work, however, is now performed by rotating cutters worked by steam power, and such beads and mouldings, of any desired pattern, can be procured better at the manufactory than they can be made by hand.