The best way is to make a pattern of wood of the desired part, take it to a brass, or iron, foundry and have it cast. It is easy then to smooth it up with a file or to machine it in a lathe, or shaper, and lacquer it when it will look like a mechanic’s job.
Fig. 75. A STANDARD FOR A TELEGRAPH SOUNDER
It is nice and easy work to make a wood pattern, that is to cut out of wood the needed part of exactly the size and shape you want the finished casting to be. The wood for your pattern should be pine or poplar and thoroughly seasoned. A scroll saw frame will come in handy for sawing out small patterns.
Where two pieces of wood are to be fastened together a good glue should be used. After the pattern is built up file out the uneven places with the kind of files made for scroll-sawyers’ use. When this is done smooth up the pattern with medium fine sandpaper and finish it with very fine sandpaper.
Should any holes or cracks show in the pattern after it has been sandpapered fill them up with putty; and, last of all, give the pattern a couple of coats of shellac varnish or rub graphite into it all over to keep it from sticking to the mold. Your pattern is now ready to be cast in metal.
Fig. 76. POURING A MOLD
A pattern, if it is complicated, should be made by a skilled pattern maker for it must be made in a certain way so that it will draw from the mold easily and without injury to the latter and leave it perfectly smooth.
Casting in Iron and Brass.—Somewhere above I said that a pattern should be the exact size you want the finished casting to be but as a matter of precise statement iron, brass and nearly all other metals shrink when they are cooling and so the pattern must be a trifle larger than the exact size you require and you must also allow for filing and machining. (See Fig. 76.)