|Small-Scale Horn Processing (ILO - WEP, 1988, 104 p.)|
|CHAPTER II. CUTTING OF HORNS|
The most commonly used method of cutting horn is cold sawing. Fine-toothed blades are used to avoid flaking. Blades used for cutting metal are the most suitable, preferably those intended for soft metals as they are cheaper and less brittle.
All the saws illustrated here were designed for a specific purpose. However, saws may be suitable for several cutting operations. All these cases will be examined in detail in the following paragraphs. A well-equipped and rationally organised workshop should possess at least one of each type of saw, but every artisan will select the type of saw that best corresponds to his or her needs and financial means. In the following diagrams, the inside of the horn is represented by a dotted line. The outline of the shapes to be cut, carved or engraved should be marked in soft-lead pencil on light coloured horns and in white chalk on black horns.
A hacksaw (figure II.1) is used for cutting along the side of a horn while leaving the opposite side intact.
This sawing method should only be used on the convex middle section of the horn, as the figure shows, to prevent the saw-end from damaging the horn-tip.
The pistol-grip handsaw shown in figure II.2 is indicated for longitudinal cutting of the horn from any angle. In addition, this type of saw is very economical as broken hacksaw blades can be used.
Figure II.1: Hacksaw
A jigsaw, as shown in figure II.3, may be used for straight cuts through the widest part of the horn, where the internal diameter is large enough for the blade to reach its lowest point without coming into contact with the opposite side of the horn.
Figure II.2: Pistol-grip handsaw
A hacksaw may be used when the horn is to be cut through its diameter, by applying the blade at right angles to the clamping device, as shown in figure II.4. In a mechanised workshop, this operation can be carried out rapidly using a bench band saw, as shown in figure II.5.
Figure II.3: Jigsaw
Figure II.4: Longitudinal cut with hacksaw
Figure II.5: Bench band saw
Figure II.6: Straight cut
When the horn is flattened, as shown in figure II.6, straight cuts can be made by a hacksaw, a pistol-grip hand-saw, a jigsaw or a band saw.
Partial or complete cross cuts, as in figure II.7, may be made with either a hacksaw or a band saw.
Figure II.7: Cross cutting
Curved cuts in a flattened horn, such as those in the outline of a salad spoon in figure II.8, may be made with a bow saw using an abrasive wire as a blade (figure II.9).
Owing to the position or shape of the cut to be made, it is not always possible to use a saw, as in the case of the feet of a heron, shown in figure II.10. To cut out such shapes, a series of holes must be drilled along the line required for the off-cut in a section of waste horn. (See figure X.2 for the finished model.)
Figure II.8: Curve cutting
Figure II.9: Bow saw
Figure II.10: Cutting by drilling a series of holes
The diameter of the holes may vary from one cut to another. If the diameter is too small, it will be necessary to make a large number of holes. If it is too large, the edge of the cut will be too rough. In most cases a drilling diameter of 5-6 mm is recommended.
Discs, such as those used in the production of buttons, can be cut rapidly with a bit of the type illustrated in figure II.11. Ring blanks can be drilled and cut in a single operation using a bit of the type shown in figure II.12. These two types of bit can be used with a hand drill or an electric drill.
Figure II.11: Bit used to cut discs
Figure II.12: Bit used to cut ring blanks