L, large wheel of 96 teeth driven by the wheels and pinions I, J, K, and forming the foundation of the third part, M, which carries the nose of the chuck.
N, N, self-adjusting radius plates for carrying the various change wheels, &c.
O, P, the eccentric slides of the first and second parts.
Q, R, the screws working the eccentric slides.
[A Paper on the Principles which Govern the Formation and Application of Acute Edges, with special reference to Fixed Turning-tools, contributed by Mr. Dodsworth Haydon.]
"The formation of the tools used for turning and planing the metals is a subject of very great importance to the practical engineer, and it is indeed only when the mathematical principles upon which such tools act are closely followed by the workman that they produce their best effects."—Holtzapffel, vol. 2, p. 983.
As the best lathe can do no more than place the work in the most favourable position for the operation of the tool, and the best tool can only do good work when applied as well as constructed on true principles, no argument is needed to prove the truth of the statement taken as the text of this paper.
But while many of our most eminent practical authorities, such as Nasmyth, Holtzapffel, Babbage, Prof. Willis, and others, have contributed valuable papers on the subject, no single writer can be said to have embodied all that should be known upon it as a whole.
Principle may be looked upon as the essence of practice, and in connection with this particular subject, the reduction of practice to principle is of comparatively modern growth. This will account for the fragmentary character and occasional difference of opinion, which marks the treatises of the above-named eminent authorities when compared with each other. As a step towards some more concise and perfect code of principle, I have endeavoured to collate and arrange in consecutive order, all those laws which govern the action of acute edged turning tools.