Although technically a "plastic" is any material that can be molded or formed, for the purpose of this manual the term will be applied only to synthetic resins which are capable of being worked with hand tools or light power tools. The appeal of plastics as a craft material is due to the ease of working, the brilliance of the finish so easily attained, and the rich colors available in various types of the material. Objects of plastics require no painting or other coatings, since their color and finish are inherent in the material itself. Wherever the cutting stops, a little smoothing and polishing will bring out a surface that is just as brilliant whether it is produced with a rag in the hands of a novice or with expensive professional equipment. In this material, more than any other, the craftsman can secure results that are the equal of professional work in every respect, with a minimum of equipment and experience.
A wide variety of materials is available, both from scrap sources and regular suppliers. The most common is acrylic resin (Lucite or Plexiglas), widely used in bomber noses and other aircraft parts. This is the most easily worked of all plastics, its only disadvantage being that it is not available in colors, although there are methods of tinting it. It comes in clear, transparent sheets of various sizes up to 40 inches wide, and in thicknesses up to 1 inch, with 3/16 inch and 1/4 inch most common. Round rods up to 1/2 inch in diameter are also available occasionally.
Almost as common and as easily worked is cellulose acetate (Lumarith, Acetate, Plastecele. Tenite, etc.). This is most frequently encountered in sheet form, from .005 to .040 inch thick, in clear and various transparent and opaque colors. Commercial objects such as combs, toothbrush handles, knobs, etc., can be used as a source of this material and carved into smaller objects, or cemented to make larger ones.
The third large class of plastics suitable for craftwork comprises the cast phenolic resins (Cata-lin, Bakelite, Resinoid, Marblette, Gemloid, etc.). These materials, while slightly harder to work, and not offering the freedom in heat-forming found in the above mentioned materials, are available in the most brilliant and variegated colors, hold their polish longer and are stronger. For these reasons they are preferred by many experienced workers.
Plastics definitely not suited for craftwork are those machine-molded materials containing mineral or other fillers. These can never be polished to a high finish because of the filler, and cannot be bent or heat-formed because they are "thermo-setting," that is, made rigid and relatively brittle by the heat applied in molding. While there are countless varieties and trade names for these materials, the public usually refers to them as "Bakelite". They may be identified by the rough, crumbly appearance of a fractured piece.
Various other plastics have been developed in recent years which are more or less suitable for craftwork, but the acrylics, cast resins and acetates mentioned above are the only ones commonly available. However, practically any plastic material which breaks with a clean, glass-like fracture can be worked by following the suggestions given here for the other materials. Among these are vinylite, urea formaldehyde, and others.
The plastics mentioned above can be worked with almost any of the hand or power tools designed for use on wood or metal. They may all he bent or formed by the application of heat, and may be cemented by the use of solvent cements which make the joint of the material itself. Various operations possible include sawing, drilling, carving, turning, bending, engraving, tinting, inlaying, filing, sanding, and polishing. The only operations not possible are those commonly employing sharp-edged tools such as knives, planes, etc.
Equipment may oe as simple or as elaborate as conditions permit. Minimum equipment required for handwork includes a fret-saw and hack-saw, a hand-drill, files and clamps. Power tools in the order of their desirability are a buffing and polishing wheel, a sander, a hand electric grinder, a metal or woodworking lathe, a drill-press, a jig-saw or band-saw and a circular saw.
The most necessary supplies are medium-fine and fine sandpaper, buffing and polishing compounds, cements and "findings," which include small drive-screws, hinges, metal ornaments, clasp-pins, and other items commonly used in the costume-jewelry trade.
All of the rules for working soft metals apply to the working of plastics. Saw-blades should be medium to fine-toothed, with little set. The material breaks saw-blades easily if it is not securely held, but it should not be clamped in a vise without some protection, as it is easily marked by pressure. A simple method for holding flat sheets while fret-sawing is shown (fig. 108). In general, the type of blades intended for use with metal are preferable to the coarser wood-working blades. Moreover, the finer-toothed the blade used, the less filing and sanding will be required later to prepare for polishing.
For all ordinary work, plain twist-drills ;are used at the usual soft-metal-working speeds. ;If much drilling is to be done with drills of 1/4 ;inch and larger, the drill angle should be altered to 90° as for working in brass (fig. 109). Use only moderate pressure, backing out frequently on deep holes to clear chips and avoid heating, and slackening up on the pressure as the bit emerges from the under side. No lubricant or coolant is needed except for production work.
Any type of file may be used in shaping the material, but the most necessary files are the finer ones of various shapes (flat, square, round and triangular) which are used to remove tool-marks prior to finishing. Files should be rapped frequently to clean them or rubbed across end-grain wood or a file-card, as they clog up quickly.