Introduction

The distance at which the axis of the lathe mandrel stands above the surface of the bed or bearers, upon which the lathe heads are carried, called the height of center, is used as the term to designate the dimensions of all lathes; and this measure being at the same time the radius, it also indicates the possible diameter of the surface, that may be turned in any particular lathe.

Plain foot lathes, vary from about three, to occasionally eight or nine inches in height of center, and in most cases the lathe heads, mandrels, chucks, and other apparatus are made of proportionate dimensions and strength; the bearers and frames, also increase in length about relatively. Lathes of the lesser dimensions, although sufficiently suitable for some few specific purposes, frequently prove inconvenient when applied to the general requirements of turning, from the very limited range of work to which they are adapted; and also, from the almost unavoidable want of stability throughout their various parts. The latter disqualification being made more prominent by reason of the very smallness of the lathe, which renders its use to the utmost extent of its capacity constantly inevitable. The larger of the foot lathes are infrequently met with, generally on account of the great labour required to drive and manipulate the comparatively ponderous apparatus, these therefore, are usually only required and made to meet some exceptional circumstances.

The 5 inch center foot lathe may be considered as the mean in point of size, and also upon examination, as in many respects the most convenient and efficient of the foot lathes for the generality of plain turning, and especially so for the amateur. With very few exceptions the works executed in the foot lathe, of necessity either in their material or construction, consist of forms built up, or made of a more or less number of parts of varying size, joined by fitting or screwing to each other; any one piece of which, rarely exceeds the limits of length or diameter to be obtained in the five inch center lathe.

On a comparison of the working of the five inch, with that of the lathe of four inch center or even less, the friction arising from the increased size of the mandrel and other working parts, is so completely within the limits that are convenient to the operator, that it may be disregarded as of no practical importance; the increase in the power required in driving the first, being often hardly discernible. On the other hand, the proportions of the several parts of the five inch center lathe, are found to be those most completely in accordance with convenient manipulation; while they are at the same time sufficiently large to permit of efficient construction with consequent stability valuable for all classes of turning, together with sufficient capacity in the length and diameter of the work. All of which also, in no way interferes with the production in the same lathe, of the most minute and delicate turning.

Some of the foregoing, might appear as arguments to still further add to the height of center; were it not, that the five inch lathe when correctly proportioned, is also found to be sufficiently large and stable, to permit its height of center to be temporarily increased, for the occasional purposes for which this proves necessary, by other means described in the succeeding chapter. It must also be admitted, that a further increase in the dimensions of the foot lathe and its adjuncts, soon tells in the weight and friction of the working parts and the power required for driving, with proportionate increase of cost, without corresponding advantages.

The correctness and truth of the work produced, depending primarily upon that of the lathe heads and mandrel, these usually receive most careful construction, and should also be of the best materials, to ensure their permanent accuracy. The lathe heads and mandrel, which, it may be permitted to be said, can hardly be too good in quality for all purposes of turning, may then be mounted upon frames constructed either with a view to economy, or to the highest attainable accuracy; and the remaining portions of the lathe completed, according to a similar scale and to agree with its ultimate purpose.

It would considerably extend these pages, and it is thought would hardly offer commensurate advantages, to attempt to collect and describe every variety that has been introduced into the form of the modern foot lathe; for, and in many of which, it is often sufficiently obvious, that there is neither satisfactory reason nor practical advantage. The more usual forms of the plain and other lathe heads therefore, together with those of the frames and other parts of the apparatus, which are referred to in the following pages; will, it is hoped, be found to afford sufficient types. The lathes described are grouped with a view to a gradually rising efficiency; from those suitable to plain turning, to those, which still intended for this purpose, are more comprehensive and are also adapted to be the foundation, for the addition of apparatus for special purposes and for ornamental turning. The descriptions of the various parts will also afford an opportunity to lay before the reader, such information upon their use and construction as may appear desirable in this place; while more extended notices demanded by individual portions, and also some particulars of additional apparatus, in less constant use, but meeting many requirements in plain turning, are collected in the succeeding chapter.