This section is from the book "Lathe Design, Construction And Operation, With Practical Examples Of The Lathe Work", by Oscar E. Perrigo. Also available from Amazon: Lathe Design: Construction And Operation.
It was later found that if the flexible pole or "lath" was rather weak and the piece of work to be operated upon was quite heavy, acting as a balance-wheel, its forward revolution was not wholly arrested, but only checked as the foot was raised, provided the cutting-tool was withdrawn from contact with the work a moment before the upward motion of the foot began.
By this it was seen that great advantages might be gained if the lathe could be made to not only revolve continuously in the direction of the tool, but also with the same force, whereby the tool might be kept in constant contact with the work.
Already the pulley, as applied to the spindle of the lathe, was known. The cord wrapped around it and used to rotate it was known. Doubtless an assistant had furnished the power to drive the lathe while the mechanic handled the tools. What would be more natural than the arrangement of a large wheel, journaled to a suitable support at the front or rear of the lathe, and having the cord connected with it as a driver. And with this device and the problem of revolving it by hand, a handle set between its center and circumference would be natural also, and thus came the crank. We do know that somewhat later than this machines were driven in exactly this manner, the large wheel being constructed with a heavy rim and acting as a balance-wheel.
At this stage of development the large driving-wheel was rather an attachment than a part of the machine itself, and doubtless so remained for a considerable time. The next change was to locate it beneath the lathe bed, directly under the head-stock, and instead of the use of the handle forming practically a crank of long leverage it was constructed as it is in the sewing-machines of the present day; that is, the wheel journaled upon a fixed stud and the previous long handle reduced to a wrist-pin for the attachment of a connecting rod, or in the older phrase a "pitman," which term was given to one of the men handling the vertical saw used in sawing up logs into timber and planks in the olden times (and even now in oriental countries), wherein the log was supported over a trench or pit, the upper end of the saw being handled by the "topman" and the lower end by the "pitman" or man in the pit. When these saws were later on mounted in a rectangular frame or "gate" having a vertical, reciprocating movement and operated from a crank-shaft by a connecting rod from the one to the other, this rod took the name of the former man who performed this office, hence the term "pitman."
The location of this pitman or connecting rod, as has been said, was directly under the head-stock and well within the convenient reach of the operator when attached to a suitable "treadle" whose rear end was pivoted to the back of the machine and whose front end formed a resting-place for the operator's foot. This arrangement answered very well and was useful when the work of the lathe was near the head-stock, but was not adapted to long work, to accomplish which the operator would need to stand near the tail-stock or even midway between that and the head-stock. To remedy this defect a strip of wood was hinged to the front leg of the lathe at the tail-stock end and its opposite end to the front end of the treadle. This was of considerable use, its principal drawback being that while at the treadle end its vertical movement was the same as the latter, this movement was gradually lessened until at the tail-stock end of the lathe it was nothing. Hence, much more power was required to drive the lathe at its center than at the head-stock, and this was rapidly increased as the work was nearer the tail-stock end of the lathe.
To remedy this defect the large driving-wheel was mounted upon and fixed to a revolving shaft upon which was formed two cranks, one near the wheel and the other at the tail-stock end of the lathe. This shaft was properly journaled in boxes formed upon or attached to cross-bars fixed to the legs at each end of the lathe. From these cranks hung two connecting rods whose lower ends were pivoted to two levers pivoted to the rear side of the lathe, and whose front ends were connected by a wooden strip or "foot-board." The length of these levers was such that the movement of the foot-board was about twice the "throw" of the cranks, so that with a foot movement of twelve inches the two cranks were about three inches, center of shaft to center of connecting rod bearing.
This was then and for many years the prevailing form of foot lathes and was quite extensively used, not only for turning wood but for iron, steel, and other metals as well.
There were many of the older mechanics who would work the entire day through. At that time a day's work was not eight, nine, or ten hours, but "from sun to sun," or from daylight till sunset, day after day, treading one of these foot lathes and turning out a much larger quantity of work than these crude facilities would seem to render possible.
In Fig. 5 is shown this form of foot lathe that was in use for many years for turning both wood and metals. The illustration is a drawing of a lathe built by the author when he was between fifteen and sixteen years of age. The bed A, legs B, the cross-bars C, C, the back brace D, and treadle parts E, F, were built of wood, as was also the tail-block G, which was of the form shown in Fig. 4, except that beneath the screw forming the tail center was a wooden key g, for keeping this screw always tight, as there was a tendency, from strain and vibration, for the screw to work loose.
The tool-rest was of the usual form, except that instead of a wedge, in connection with the binder H, to hold it in position, or the use of a wrench on the holding-down bolt, an eccentric of hard wood with a handle formed upon it, as shown at J, was used. This was the first occasion where the author saw an eccentric used for a similar purpose. It worked so well that he fitted similar eccentrics to the stops of the three windows in his little workshop to hold the sashes in any desired position when they were raised, and by a turn in the opposite direction to secure them when they were closed.
Fig. 5. - Foot Lathe for Turning Wood or Metals.