PRACTICAL PAPERS—IMPROVED MACHINERY. 
327 
IMPROVFD MACHINERY. 
From the Government Report of 
F. A. P. BARNARD, LL. D., 
United States Commlasioner to the Paris Exposition of 1867. 
Armstrong’s dovetailing machine. 
The exposition contained four or five machines, all more or 
less ingenious, for performing the rather difficult work of mak¬ 
ing dovetail joints. Of these, the most expeditious in its ope¬ 
ration, and as satisfactory as any in performance, was the 
American machine bearing the name of the patentee, Arm¬ 
strong of ISTew York. Without complete drawings it would 
be impossible to convey an idea of the action of the machine 
in all respects; but the essential and most important part is 
shown in the figure annexed. It will be seen that there are 
two disks mounted on axes inclined to each other, as well as 
to the main driving-shaft, and revolving at the same speed, the 
one being inclined to the right and the other to the left, the 
motion being transmitted from the first to the second disk by 
means of bevel wheels cast on their inner surfaces. Each 
disk has on its outer circumference a spiral groove making one 
complete turn, into which is fitted a saw composed of seg¬ 
ments, so arranged as in one complete revolution to give both 
the longitudinal and transeverse cut necessary to finish a dove¬ 
tail, one-half being made by one disk and the other half by 
the other. The leading portion of the saw is composed of 
segments similar to those that could be cut from an ordinary 
fine-pitched circular saw, while to produce the transeverse cut, 
after the longitudinal one is finished, the segments assume the 
form shown in the engraving, from an inspection of which the 
