Incising is used where very deep, narrow lines are desired. It requires a good deal of skill, and the beginner will do well to practice on scrap leather before using it in a project.
The pattern is transferred to the leather as above. While the surface is still damp, take a very sharp knife and cut along the lines of the design to a depth of about l/4" that of the leather (fig. 25).
If the cut is too deep, the white edges of the incision will show when the leather is bent and the whole article will be weakened. When the cutting is completed, go over the lines with the narrow end of the modeling tool pressing the incised edges down firmly. This step is also shown in the illustration.
Various geometrical patterns can be indented in leather by the use of background stamps (fig. 26).
These may he purchased or you can make your own by filing designs in tool steel or the heads of nails. (See ch. 5.) The leather is dampened and laid face up on the marble slab. The stamp is then placed on the leather and struck lightly With a mallet. Practice will show how heavy a blow is needed to leave a clear mark on the surface.
Blind tooling is a variation of this method. The pattern is first worked out on paper by inking the stamps on a stamp pad and pressing them on the paper pattern in the desired arrangement. The pattern is then placed over the damp leather, the stamps are carefully aligned over their marks on the paper and are pressed down by hand just enough to leave a faint impression on the leather. The pattern is then removed, and the final stamping is done with the mallet as above. The faint impressions made through the paper act as guides for the real stamping and are useful when a complicated design combining a number of different stamps is to be used.
Nontooling leathers can be stamped without moistening the leather by heating the metal stamps and pressing them by hand into the surface. To insure the correct temperature for this type of work, hold the stamp in a flame, then touch it briefly to a damp rag. As soon as it stops sizzling it is ready to use.
The embossing wheel, which can be purchased in a variety of patterns, is really a cylindrical stamp used chiefly for borders (fig. 27). The leather is dampened, and the tool is rolled along the edge with enough pressure to leave a clear imprint on the surface. It can also be guided by the metal rule if necessary.
The first step in assembling a leather article is to mark and punch holes for the stitching or lacing which will hold the various parts together. Even articles made of a single piece of leather are often laced along the edges to prevent wear and give a more finished appearance.
It is important that the holes for lacing be evenly spaced and that they run exactly parallel to the edge. The distance between holes should be about the same as the distance from the holes to the edge. This distance will vary from about 1/8 inch to inch depending on the weight of the leather and the size of the lacing thong.
The easiest way of marking the leather for punching is to run a spacing wheel over the face of the leather, guiding it with a ruler on straight lines (fig. 28). If such a wheel is not available, lay a ruler along the edge to be laced and mark the leather at regular intervals with an awl or the small end of the modeling tool. Make sure that there will be a hole squarely in the middle of each corner even if it means adjusting the spacing of the holes between the corners somewhat.
When two pieces are to be joined, mark and punch the first one, then lay it carefully on top of the other. The second piece is then marked with an awl through the holes of the first piece so that when punched the openings will coincide perfectly (fig. 29).
Lacing is generally done through round holes which are made with a drive punch and a mallet or with a spring punch. The drive punch is centered over the mark and tapped with the mallet. Drive punches come in several sizes of which the No. 0 is most widely used for small articles (fig. 30). The spring punch of the type illustrated has a revolving head bearing punches of different sizes (fig. 31).
It is quicker and more accurate than the drive punch.
For certain types of lacing, a slit is preferable to a round hole. These can be made with a three- or four-pronged chisel (fig. 32). A single-pronged chisel will also be needed for the corners.