J. Pocock - Model Engine-Making: In Theory and Practice

I NDEX

TOOLS AND CASTINGS.

T HERE may be those who, never having tried their hands at model engine-making, are ready to maintain that such work is a mere waste of time; but, as a matter of fact, there are few leisure occupations better calculated to train the hand, eye, and mind all at one and the same time, and to such good effect. Not only does it afford a most thorough training in all such descriptions of mechanical work as lie within the compass of an amateurs powers, as filing, drilling, turning, fitting, screw-making, etc., but a considerable amount of knowledge is also acquired as to the theory and practical application of steamthe most important power of the present day. Nor must it be forgotten that James Watt himself, although he had previously by means of a Papins digester and a syringe made a few experiments, might nevertheless have failed to turn his attention seriously to the improvement of the steam-engine, had it not been for the model engine placed in his hands for repairs by the authorities of the College of Glasgow; and while we continue to obtain from the steam-engine as at present only a small proportion of the energy theoretically contained in the fuel consumed under the boiler, who can say but that the model-maker of to-day may be a second James Watt to-morrow ?

Although many of the so-called model engines as, for example, those described in Chaps. II. and III.have no large and useful archetypes, still the construction of these will prove a valuable stepping-stone to the more advanced models described in later chapters; and in order to impart as much interest as possible to the work of Model Engine-Making, I have in many cases given the proportions of the more important parts as they would be in full-sized engines.

Before however we take in hand the actual construction of a model engine, it will be convenient to devote a preliminary chapter to the consideration of the tools required and the castings to be used.

First, as to the tools needed, these will be such as are to be found in the workshop of any amateur who has taken up metal-turning. It is sometimes stated that, provided the cylinder is bought ready bored, a lathe is not absolutely necessary. Perhaps not absolutely, but without it much additional time and patience will be demanded, and the results both in appearance and working will certainly be far less satisfactory. I would therefore by no means recommend any one to undertake model engine-making, unless they are provided with a lathe.

A chuck for holding small drills, and a grip-chuck holding from 1/4-inch diameter upwards, will be found useful adjuncts to the lathe; and if the lathe is provided with a face-plate, so much the better.

A few small chisels of the shapes shown by Figs. 1 to 5, must be made from good square cast steel : these are for chipping out steam-ports and similar work.

A few drills from 1/16-inch up to 1/4-inch, of the ordinary shape, will be necessary; and D-bits of the required sizes may be made as wanted. Fig. 6 is a section of a D-bit at its cutting end, and Fig. 7 is a section taken at a little distance down the shank.

A rimer (Fig. 8) will be found useful. It is made from a piece of small steel rod, filed up to a triangular or five-sided shape, and tempered to straw colour.

The usual gravers, round-nosed and other turning tools will be required, also one or two inside tools; and a few files, flat, half-round, and triangular, coarse, medium, and fine. A bench vice is almost as indispensable as a lathe; and an Archimedean, or some other form of hand-drill, for small drills will often be found handy in addition to the drill-chuck already named.

A small steel square, usually known as an engineers square, must be included in the list of tools required.

One or two scrapers will also be found useful. These may be made from broken files, the teeth being ground out for a short distance from the broken end of the file, and the end ground off straight across. These scrapers are to be used for giving the finishing touches to such work as cannot be got sufficiently level by filing.