The Lathe & Its Uses / Or, Instruction in the Art of Turning Wood and Metal. Including a Description of the Most Modern Appliances for the Ornamentation of Plane and Curved Surfaces. With an Appendix, in Which is Described an Entirely Novel Form of Lathe for Eccentric and Rose Engine Turning; a Lathe and Planing Machine Combined; and Other Valuable Matter Relating to the Art.

by James Lukin

[19] This part is always so turned by the best makers.

This handy apparatus will be found on a later page fully described and illustrated by a photograph of the machine. The writer has seen it and used it, and can testify to its satisfactory working, as a lathe thus fitted does not run heavier or require greater exertion than when used for ordinary turning.

The next step will be the chamfering of the edges of the plate. Let 235 represent the plate in its present condition, with rectangular edges. To produce a chamfer of 45°, draw a line, a, b, at a distance from the edge equal to the thickness of the piece. If a smaller angle is desired, the line must be drawn further back. An angle of 30° to 35°, is, in the writer's opinion, better than one of 45°, as the chamfered bars will then have a wider bearing on the upper surface of the plate, tending to hold it more securely down upon the lower part of the chuck. Nothing remains but to file carefully down from the line thus drawn to the lower edge, by no means a difficult operation if care is exercised not to obliterate the mark, or to trespass the least beyond the assigned limit. A template, cut like [Fig. 236], of the desired angle, will be a gauge for the edges of the plate, as well as for those of the chamfered bars, and will serve to make assurance doubly sure. The arms which stand out at the back of the slider to embrace the guide ring are not fastened to the plate immovably, but with power of adjustment. A pair of short slots are made in the slider, into which a square projection from the arms fits, and the whole is clamped by a screw, as shown in [237], A, B, and C.

Figs. 235, 236, 237.

A more accurate method is shown in the [Ornamental Section] for finer adjustment than can be secured in this way, but for a home made chuck the above will suffice and is the easiest plan to carry into effect. To use this chuck, the guide is first arranged, so that its ring is concentric with the mandrel. A mark is generally made upon it, and also upon the lathe-head, by which this position can be readily insured. The chuck is then screwed upon the mandrel, and the arms adjusted, as just described, so as to embrace accurately, but not too tightly, the guide ring. They are then, once for all, fixed in that position by the screws alluded to. A few drops of oil are necessary to lubricate their inner surface and the exterior of the guide, and the latter being withdrawn by its adjusting screws to the desired eccentricity, the work may be proceeded with. A rough piece of wood, however, should always be first turned to a cylindrical form, as an oval chuck being an expensive article is to be carefully preserved, and not exposed to the shocks inseparable from the process of roughing down the work. Moreover, there should always be one or two screws passing through the slider into the back plate, to take away the strain from the chamfered bars, which can be removed when the slider is to be brought into action. Two precautions are here laid down respecting oval turning, which, in all probability, a tyro would not suspect to be necessary until taught by failure. In the first place, at whatever point of the circumference the tool is held, at that point it must remain, or rather, it must remain in the same horizontal line, being neither raised nor depressed. Hence, for all work where accuracy is needed, oval turning should be done with the slide rest. In the second place, when it is desired to place a succession of ellipses one within the other on the face of the work, like [Fig. 229], it will not be sufficient to place the tool nearer to the centre for each ring, but the eccentricity of the guide ring must be reduced at the same time; otherwise, when the middle is reached, a straight line will be the result, instead of the proposed ellipse, as already stated. The lathe should not be driven at a very high speed, and the moving parts should be lubricated from time to time. There are other ways of compensating the error produced by the oval chuck, or elliptic cutting frame, which however are so entirely connected with ornamental turning that they are reserved to be introduced into that section. A contrivance for turning ovals invented, and communicated to the English Mechanic by a Suffolk amateur, deserves a place here. It is thus described by the inventor:—

[Turning Ovals, etc., by Means of a Template.]

Ovals are generally turned by causing the work to move in and under guidance of an "oval chuck".

There seems no reason why the same result should not be arrived at by communicating a movement to the rest supporting the cutting tool in the following manner:—Let A, A, be lathe bearers, B, pulley, C, screw of mandrel, D, template fixed thereon, E, friction wheel on the end of bar F, G rest (a board of any convenient width) moving on pivots at H. The friction roller, E, is to be kept in contact with the template by the cord running over the pulley T, stretched by the weight L. The rest will thus oscillate under the guidance of the template, which may be either oval or rose engine pattern, and the cutting tool form the pattern of the template used. There might be other modes of causing the rest to oscillate on the same principle. The lathe would require a slow motion, the same as with an oscillating mandrel.