Fig. 158.—Knocking out Iron of Jack Plane.
Fig. 159.—Cutting Iron.
Fig. 160.—Cutting and Back Irons.
Fig. 161.—Badger Cutting Iron.
Fig. 162.—Badger Cutting and Back Irons.
Fig. 163.—Unscrewing Plane Irons with Special Tools.
ADJUSTING PLANE IRONS.
The manner of handling and adjusting the cutting iron is a most important consideration, especially when planing against the grain of a brittle wood, such as pitch pine. In planing wood that is cross-grained and liable to rip or tear up, the cutting iron should be set very finely—that is, its edge should be quite close to the edge of the back iron (see Fig. 167), but for the jack plane it must be placed further back, as at Fig. 165. The finer the shaving to be taken off the wood, the closer should it be set. When dressing a difficult wood against the grain, although the cutting edge may be in splendid condition and sharp as a razor, the perfect condition and adjustment of the back iron is also an absolute necessity in order to leave a fine smooth surface. The finer the shaving the smoother will be the surface obtained; and if the edge of the back iron, as it is lying on the cutting blade, is in the least degree rough or does not press evenly and firmly on the whole width of the blade, the shaving will get in between and stop the work. However, it is easy to set the iron too fine, especially when jack-planing soft, straight-grained stuff like pine, which perhaps wants considerably reducing.
Fig. 164.—Unscrewing Plane Irons with Long Screwdriver.
Fig. 165.—Plane Irons Tightly Screwed.
Fig. 166.—Plane Irons Loosely Screwed.
SMOOTHING PLANES.
This plane, as its name implies, is for the purpose of smoothing the work to form a finished surface. After the drawing in, mortising, tenoning, dovetailing, etc., are done, and before the work is put together, all the parts that cannot afterwards be operated upon are finished with this plane. For fine or other soft woods it is 9 in. long, having an iron 2 1/4 in. wide on the cutting face. The stock of this plane has the sole and top parallel, but the sides are curved, making the two ends narrower than the centre. The wooden smoothing plane (Figs. 168 and 169) has not a toat or handle, but the iron plane has a toat; for general usefulness, however, the plane made of beech cannot be excelled. This plane is specially shaped with a view to the extreme handiness indispensable to a tool that has to contend with varying directions of grain in the wood. Hard woods, particularly the more ornamental kinds, often are troublesome to clean off, and however well the smoothing plane is used, much must still be left to the scraper. The conditions of successful work with the smoothing plane will repay study, since practical experience of those conditions will tend to the more skilful handling of the larger planes. The sole of the plane should be flat; tested in any direction with a straight-edge the result should be agreement, but in the case of the iron-fronted plane (Fig. 169) the sole is curved lengthways. The cutting iron should rest on the sloping surface prepared for it without any rocking, touching all over the surfaces in contact. When the back iron is screwed on, the same condition should obtain. Hence the flexure caused by tightening the screw should be mainly taken by the back iron, whose object is to stiffen the cutting iron and not to distort it. If, therefore, the cutting iron, with the back iron affixed, is in winding, either the bed of the iron in the plane is bad or the plane must be fitted to suit the winding iron. A little further consideration will show that (1) the warping of a plane involves alteration of the surface on which the iron rests; that (2) it is desirable both that this surface be flat and that the plane iron be flat on its back surface; and for these reasons it will be found (3) that “parallel irons” are far superior in stiffness and accuracy to the ordinary plane iron. The wedge also must fit so well that the iron may rest immovable under ordinary working strains; but it is not fair to expect the wedge to force into agreement crooked irons and warped planes. It should never be necessary to drive the wedge so tightly that its withdrawal becomes difficult. As the function of the back iron is to stiffen the cutter and deflect the shaving, care must be taken to avoid breaking or bending the edge of the back iron. A gap into which a part of the shaving could get must not be allowed to remain, and rounding or under-cutting of the contact edge must not be permitted. The upper surface of the back iron is to be kept clean and smooth, so that the shaving may glide up its polished surface. The sharpened edge of the cutting iron must be a little convex, but only sufficiently in most cases to prevent the corners of the iron digging in. It is therefore necessary to sharpen the irons of all planes with some attention to the thickness of the shaving they will be required to remove, and to sharpen away a little from the corners of the iron accordingly, diminishing the convexity for trying and smoothing planes, but increasing it for jack planes, which are intended to be coarsely set. It might be thought that this convexity would produce hollows in the work, but it must be remembered that the iron is not used upright, but at an angle which will reduce the convexity about one-half. The aperture or mouth of the plane should be as narrow as possible, so as not to encourage tearing up. The passage of the shaving without hindrance is all that is desirable; but the mouth should be so formed that it may be possible to bring the back iron edge very close to the cutting edge, and still allow the shaving to pass freely. However well the smoothing plane is set, sharpened, and used, the scraper and glass-paper are still required for finishing hard woods. The plane iron is knocked out in quite a different way from the jack plane. Hold the tool in the left hand, as in Fig. 170, with the thumb on the inside of its mouth, and with a hammer held in the right hand tap the back until the wedge is loosened sufficiently to admit of the iron being withdrawn. Beginners, as a rule, will hammer away at the top of the plane, as with the jack plane, but this is neither desirable nor necessary.
Fig. 167.—Adjusted Plane Irons.