Cast resin plastics can be worked with anything from a nail-file to a million-dollar factory—and to look at the finished product in each case, it would be difficult to guess which instrument has been employed, for the reason that the beauty and finish of the job is already imbedded in the material itself, and can be brought out as easily and completely by an amateur with a rag as it can be in the big factory's tumbling barrel.
In discussing the equipment requirements for working plastics therefore, the answer depends entirely on the amount of money available, the speed and ease desired, and similar requirements. Plastics can be worked with any hand or power tool designed for use with either wood or metal, except the sharp-edged tools such as knives, planes, etc.
For pure handwork, the meagerest requirements are a set of files, a hand-drill and set of bits, a fret-saw, and any type of fine-toothed saw, such as back-saw, hack-saw, etc. This of course is in addition to supplies such as buffing and polishing compounds, sandpaper, cement, rags and felt polishing-sticks, home-made, which are explained in a succeeding chapter.
The files should be of various sizes and shapes for carving and finishing, and wherever there is a preference, the coarser-toothed should be chosen, as these do not clog up so readily. Ordinary twist-drills, or straight screw-sinking points can be used for boring holes, but not the type of wood augur having a screw point. Smaller-sized drills, up to can be used unaltered, but larger sizes should have the cutting-edge ground straight, paralell to the length of the bit, as otherwise, it might "dig in". (See Figure 3).
Additional equipment that will be highly useful to the craftsman working in plastics without power tools can be home-made, such as a special mitre-box for sawing cylinders, a simple bench "hold-down" to clamp the material while it is being fret-sawed or carved, and felt polishing-sticks which make the rubbing operation easier.
Fig. 1. Bench hold-down device, to grip work being fled, carved. Jig-sawed, etc, by hand.
The bench "hold-down", illustrated in Figure 1, is likewise very simple in construction, consisting only of a piece of plank, pointed at one end and squared at the other, with a leather strap passing thru this plank and the bench-top, ending in a stirrup at the bottom. In use, the piece of plastic material being worked on is laid on the edge of the bench between the bench and the plank, the foot is placed in the stirrup, and pressure applied, clamping the work but permitting it to be easily turned or moved about as desired.
For hand buffing or polishing, a few file-shaped sticks should be made, of various cross-sections, such as flat, triangular, rounded, etc., and covered with felt or heavy wool or flannel glued on. These should be about a foot long. In use, the stick is first rubbed on the cake of buffing or polishing compound, and then rubbed briskly b?ck and forth on the plastic object. One set of sticks should be kept for buff and one for polish— the two should never be mixed. For certain work, another set of sticks covered with sandpaper might also be useful.
If funds are limited and only one tool at a time can be purchased, by far the most important is a buffing-wheel, as this can be made to serve many purposes, and it eliminates the slowest and most tedious operation of all, which is hand polishing.
Any motor at all is better than none, but the ideal size for polishing and finishing is at least a quarter-horsepower. Even a bigger motor can be used with advantage, as the more power that can be applied, the faster the work will progress, and practically every surface has to be finished on a plastic project.
Either a motor with a double-end spindle, with nuts and washers on each end, or a double-ended buffing head with long spindles, should be secured. The ideal size for small shop use is an eight-inch loosely-stitched cotton wheel, with about a one-inch face or wider, which should be driven at about 2500 R.P.M. If you are only able to secure the type of buffing-wheel which has several rows of stitching, making it very hard and stiff, the outside rows of stitching should be ripped out, as a hard wheel not only has a tendency to heat up and burn the material, but in addition the fibres of the wheel do not have an opportunity to get down into the cracks and crevices in carvings. You must have two wheels, one for use with buffing compound and one for polishing, and even possibly a third to be used clean, with nothing on it, for the final touch, and a wheel once used for one purpose should not be used for another. Moreover, never use these wheels for buffing or polishing any other materials such as metal, as they are likely to become discolored and cause trouble when you want to use them again for plastics.
Additional useful equipment which can be used on buffing-head are a drill-chuck which can be screwed onto the right spindle end and used for drilling as well as for a certain amount or carving, by chucking in it the type of carving-cutter that will be described in a later chapter.
Also extremely useful and important is a coarse grinding-wheel, the coarser the better, which is used for shaping, rough carving, etc. An entire ring of the cabachon type can be shaped in two or three minutes on a grinding-wheel. The finer grades however clog up rapidly and burn the material; coarse carborundum wheels keep themselves clean. High speeds, around 2500 r.p.m., should be used here also; higher than that if you use a wheel of less than 8" diameter. This wheel, unlike the buffs, can be used for other purposes as well, if you are careful to clean up all of the plastic grindings before attempting to grind anything that will make sparks. Cast resin plastics, while absolutely non-inflammable in a solid piece, will smolder and oxidize slowly when ground to powder form.