Carving with power-driven cutters of various types is infinitely faster of course than carving with hand-tools. Given the proper type of cutter, and sufficient power, the material practically ' melts away" when presented to the cutter, and you feel as if you were working in soft modelling clay. Even with a crude power setup and home-made cutters, the effects gained are entirely satisfactory, even if not quite so fast.
Moreover, the use of power tools for carving in this material is safe, as compared with carving in other materials, for the reason that the cutters will not "grab" at your fingers and knuckles as wood-carving cutters do, since they do not have the "rake" or pointed edge. The cutting edges are blunt and practically square, and you can hold your fingers against them (without pressure) while revolving, without damage.
Equipment for power-carving runs the entire gamut from the crudest home-made contraptions to the most expensive professional carving-spindles, and various types will be described.
The simplest is a coarse grinding-wheel, of any shape, mounted in a grinding-head, or on an arbor in a lathe or drill-press. Any type or shape of wheel, travelling at fairly high speed and not too fine a grain may be used. It is possible to obtain these in various shapes and thicknesses, or their shapes can be altered by using a wheel-dresser, or another piece of stone from a broken wheel, so that rounded or pointed shapes can be obtained for finer work. Even if you have complete carving equipment, you need one coarse wheel for rough-shaping, as these work very fast and handle larger surfaces than the cutters. See Plate 3-0 as an example.
The next type of carving cutter in point of simplicity and low cost is a circular saw-blade, mounted BACKWARDS. This makes it safe, so that it will not grab the work out of your hands or cut your hands, yet there is still sufficient angle in the teeth to do a good carving job, although the large diameter of the blade makes it impossible to make sharp turns or to do certain types of work. Any type of blade may be used, even to a jeweler's slotting saw, or at the other extreme, a rip-saw blade, but be sure to mount it BACKWARDS before trying to do any free-hand carving with it.
Electric Hand-Grinders The small high-speed electric hand-grinders on the market see Plates 2A and 2B are perhaps the handiest and most popular of light-weight equipment for free-hand carving, since there is such a large variety of cutters, points and other accessories available to fit them. A few shapes are illustrated in Figure 11. The fastest working cutters to use on this type of grinder are the steel burrs of various shapes. The only type of these cutters which do not work excellently is the kind that comes down to a sharp point. You will try to use this point to cut with, and all it does is chew the material up and burn it, as well as take the temper out of the tool. All cutting must be done with the outside diameter of the cutters—there is a "dead spot" at the center of the spindle-point which cannot cut. This is more noticeable and objectionable when working plastics than wood or other materials which have a more pronounced grain or granular structure. Plastics has none of either, so remember to work with the cutting edges and not with the point. Another good tool to use in these grinders is a end-mill, which has cutting edges on the sides, on the end, a sharp corner, and an open hole at the "dead spot.".
Fig. 11. Some of the many shapes in which steel cutters for use in electric hand-grinders are available. This is the handiest device of all for many different light operations on plastics, especially carving.
Dozens of other simple attachments can be made for use with these machines, one of the most serviceable of which is an ordinary round typewriter-eraser mounted on one of the mandrels available with the machines. This is used for rough finishing, and cuts quite fast, since it consists of an abrasive bound with soft rubber which wears away. The grinder companies sell various shapes of these rubber abrasive tools which provide an easy finishing method of intricate carvings if properly handled and not allowed to get hot. Other accessories consist of sanding-discs in various grades, mounted on mandrels, and sanding-drums, which are fast finishers for small surfaces. A 1" diameter scratch-brush serves the purpose of rough-sanding deep depressions, removing cutter-marks in a few seconds. A resin-bond abrasive cut-off wheel cuts a thin, fast slot, and can also be used for fast carving. A hundred different shapes of grinding-wheels and points are available in a coarse grain which does not clog badly (they also have small fine-grained points which however are useless on plastics). Mounted felt buffing wheels for buffing and polishing are also available, but these unless handled with extreme caution will "burn" as they are hard-packed, do not hold the compound, and are slow-working. Plastics require a soft, open, cool buffing-wheel, and one can easily be made in a few moments by cutting out 6 or 8 1" circles from canvas and mounting them together on a sanding-disc mandrel. The machines are furnished with a little slab of very coarse carborundum, for sharpening or dressing the grinding-wheel points and strange as it may seem, this dressing-stone will 'dress" a canvas buffing-wheel just as truly, besides leaving it with a soft, fluffed up surface ideal fo this purpose. Two such wheels should be made up, one for buffing-compound and one for polishing, and never mixed. These buffs must be trued in this manner, as otherwise there would be too much vibration from an off-center wheel at this high speed, and only the high-spot on the wheel would be working.
These hand-grinders have always been considered as pure hand-tools, used for the purposes above described, but the author has found that their power can be harnessed in a great variety of ways, until they almost become a complete workshop in themselves. There have been articles in the homecrafts magazines showing how to mount these machines on miniature beds and use them as lathes, saws and drills. In addition, the following few suggestions will show how to use them, with a minimum of set-up trouble, for cutting large cylinders, for face-plate turning of certain types, for indexing and for cutting rabbetted shoulders and grooves near edges of sheet stock.
Fig. 12. (Left). The "Lethe" consists of a round wooden Mock, with a nail driven through it into the bench, and the sheet of plastics glued to the top of his "face-plate". The hand-grinder la held firmly in the hand, or supported against a block, and the work slowly rotated against it with the left hand. It can also be used as a "dividing head" by marking it off in sections, holding the dise still at each mark, and making a swinging cat with the grinder, such as for making rosettes, etc. Use of this handy device to also illustrated la the photograph, Plate 2-A, (above).
Fig. 13. (Right). Rabetting device, using an electric hand-grinder. The shoot of plasties to slid slowly under the eutter. which to hold firmly with the other hand. (Also goo photo. Plato 2-B). Below, set-up for cutting off cylinders, also for "turning- cylinders. A cradle is formed of nails, the cylinder is turned slowly with the toft hand, against the cutter held in the right.
The "lathe" for face-plate turning illustrated in Figures 12 and Plate 2A consists merely of a round block of 3/4" wood, with a nail driven thru its center into the bench—nothing more. The piece of sheet stock is glued to the face of the block, the tool is held firmly in the hand (shimmed up to the proper height) and the face-plate slowly turned against the revolving tool, cutting the groove or other contour desired. If the tool is properly held, a perfectly smooth cut will result, as a little practise will show. A great deal will depend on the proper choice of the cutting-tool. For duplication work of course the tool should be clamped to the bench in the proper position with blocks, but most work can be done by hand.