DIAGONAL. 
‘when the ratio of oe comes : be deferibed. 
is a the 
“frame, EE, are two 
the engine, at a convenient diftance, is fixed a ftrong beam, 
“Q, refting upon the lower fide rails of the wood, and fecured 
by a itrong bolt at each end. Through the middie of this 
beam another centre {crew paffes perpendicularly, the head 
pon this is placed one 
heels to be cut, the axis 
being perpendicular, an the wheels horizontal, as reprefent- 1 
appar 
edat R. The 
axis is fecured, cann - 
us by whic 
4 iron fliding frame. 
F, ftandard for ald ga the sa frame. 
G, G, guides for the fliding fr 
‘in jig. 1 
I, te {crew in the fliding frame, (hid in fg. 19.) 
‘KK, fixture for the point of the {crew oe in fe. 19.) 
L, large wheel upon the axis of the fc 
MM, worm which works the lar ae 
‘N, handle of the axis of the worm (hid in fg. 19.) 
‘O, upper frame placed in centres. 
P, cutter and axis 
Q. Crofs beam for fupporting the wheel to be cut. 
The following parts, wholly, or partially concealed in 
the Hea plan, Ay. 18, will appear in the elevation, fig. 19. 
a {crew pafling throngh the front crofs bar of the 
upper ae ; which, by coming in fea with the front 
crofs bar of the Gliding a acts a op to prevent the 
upper frame from being see deprefled, after the 
-cutter has paffed through the part of the wheel, R, whic 
it i isa ftandard raifed f. 
bearer placed upon any con- 
venient part of the crofs-piece, V, to carry a lever, X, at 
the extremity of which a weight is fufpended, which, by over- 
oe the upper-frame, raifes it after it has been deprefied 
b s of the connecting wire Y. The frame is depreffed 
by prefling down the lever -Z, with the opérator’s foot, and 
this lever is one with the frame by another wire be- 
“tween them. . 19, the upright ftandard, U, is repre- 
tented by two rtd as if tran{parent, to 
«which the vertical axis of the wheel, R, is fecured at the 
Fig. 20, is a perfpective view of all that can be feen of the 
the 
5 
Pm 
Ss 
aq 
= 
5 
tay 
oe 
K 
pst} 
= 
Q 
— 
m 
< 
a 
“3 
N 
Sone when a 
Vou, KI. 
Acrofs m 
c 
ne a tor the {crew (partially | hid, and therefore omitted 
b 
placed at each aida 4 the engine which are in aa as in 
the two form mer figu 
; be thee on 
the axis of the cutter i and the motion communicated 
from any fhaft or drum, which moves at a proper ve- 
locity. If moved by the operator’s hand, only one end of 
the axis is to be centered, — the other, pafling gactety a 
bufh in the — is to be turned by means of a winch or 
cuted; for where the divifions are fo 
vibr of any part will produce aul ans will render 
its operation ale uncertain the engine, it 
is lly neceffary that the cutter thould i always fharp, 
and that too much preffure fhould not be applied by the foot 
during the operation. In fome of the firlt trials made, 
a confiderable deviation from the calculation was difcovered 
after the wheels were cut. In confequence of this, the en- 
tent. After fome fruitlefs attempts to corre& this, the true 
aufe was at length difcovered y the fri€tion cocafioned 
the cutter, 
came prodigiou ; t 
expantion produced Bye the heat, both i in the brafs and feel, 
mutt operate to a confiderable degree upon divifions fo mi- 
nute. To afcertain how far this was the cafe, a wheel was 
_ rapidly cut, without paying any regard to the heating either 
of the brafs or the cutter. Both were then-allowed to cool, 
and the cutter again applied gently to the different divifions, 
the engine being fhifted exactly as before, when thofe divi- 
fions which had been cut hot were found fenfibly too deep. 
e wheel was then recut, or rather pared gently, for the 
deviations were not fo great as fenfibly to heat cither the 
n always 
and the fame error never occurred 
The range of this engine is as follows: The fcrew which 
moves the fliding frame backwards and forwards was fingle- 
threaded, and contained four threads in the inch. The large 
wheel, fixed upon the axis of the fcrew, contained 144 teeth; 
and the worm, or f{croll, being alfo fingle-threaded, moved 
only one tooth at every revolution. It required, therefore, 
144 Jglerae of the fcroll to produce one revolution of the 
{crew, and one revolution of the {crew pags the fliding 
frame, and. confequently the cutter, + of an inch and as 
144 X 4 is ey » every aang of the fill moved the 
upon th 
ee parts, at each of which was formed a {mall notch, and 
a flight {pring, pene the circumference, ferved as an index. 
hus the tenth pa n could = obtai 
ute, almoft ad infinitu 
to be fully as far a could be defirable rae any oradlial pur- 
3% pole, 
