350 
“Common contrivance, the bur would ‘not rise equally on both 
Graduation. sides, and the strokes, where they mect the bounding 
“—Y~™" lines, would have an appearance of crookedness. 
Preparatory to making the divisions, the circular lines 
pas the must be drawn for limiting the length of the strokes: 
circular. these are made with the well known apparatus called a 
line. beam-compass; but it is only necessary to trace the 
lines with it. They are tobe made of sufficient breadth 
and depth by the dividing-knife, which, when sharpen- 
edas above directed ; and guided by the hand alone, 
will aptly follow the slightest mark. Pad 
_ The bur is generally taken off the lines with a tool 
Scraper, called a scraper, and then cleared with the knife. After 
this the surface is rubbed with charcoal (that from the 
willow is best) and water, which leaves the surface 
smooth, without. producing a gloss that would be un- 
pleasant to the eye. Tie 
Having been thus minute in the description of the 
tools, that of their application will be short indeed. _ 
Method of A compass ring, for instance, as before mentioned, is 
dividing cir-‘ attached to the dividing plate, for the purpose of being 
cles, graduated ; its zero, or N, being placed so, that the in- 
dex, when set to it, may agree also with the zero of the 
plate. In this position of things, the operator must 
drop the point of the dividing knife into the line on the 
plate; and, pressing the index to prevent its moving, 
cut the corresponding stroke upon the ring. He must 
be careful to hold the knife steady, and in exactly the 
same position, while he sets and cuts. His eye must 
be directed to the left side of the knife, in order that 
he may see that he holds it in contact with, and parallel 
to, the edge of the index. The index is now drawn 
forwards something more than the value of a division, 
and the knife being fixed in a second line, it is then 
pushed back into contact with it, and a second stroke 
eut as before; thus proceeding from right to left until 
the cirele is completed. | In dividing upon metals, this 
work is laborious for the hands, which will require fre- 
quent intervals of rest: during these the divider should 
examine his work with a magnifying glass. In cases 
where the hand has not power to cut the strokes deep 
enough at once, which does not unfrequently happen, 
instead of cutting twice, the operator will proceed with 
more ease and expedition, if he goes round by single 
cutting, and afterwards completes his work; for, in 
the latter part, he will not have occasion for either the 
dividing plate, or the index ; the knife, if well set, will 
follow the former strokes with accuracy and neatness. 
The bur must be worn off the divisions by rubbing the 
surface with charcoal and water, as was before done 
with the circular‘ lines; but the scraper must not be 
employed. : 
Method of Common dividing, as it applies to straight lines, is so 
dividing similar to cireular dividing, that little need be: said 
straight about it. Figs. 3. and 4. represent the necessary appa- 
Hines ratus ; the dividing knife is common to both. AA is 
PratE the pattern, and B is a scale to be divided into inches 
ccLxxvill and tenths: CCC represents what is called the dividing 
Fig. 3. & 4. square. This tool consists of'a thin tempered piece of 
steel, extending, in the line of the ‘pattern, about six 
inches, and at right angles somewhat more, and a stock 
about two-tenths of an inch shorter and narrower than 
the parallel part. This latter is formed of two pieces of 
brass ; one above the steel, and the other below it, to 
which they are securely rivetted.: The stock and blade 
are even with each other at the outside and left end; 
the projecting part of the steel, in the line of the pat- 
tern, lies upon the latter, preventing the square from 
tilting, and that at the end places the stock out of the 
way when the edge of the blade requires to be repaired. 
As it is, in some cases, necessary that the square should 
5 
GRADUATION. 
be used when placed upon the farther side of the work, — 
the two parts of the stock should both be ac at Gr 
right angles to the blade ; the best way to nannbatich 
property is this:—After having made the holes which ._ 
are to receive the rivets, remove the steel, and pinthe 
two branches of the stock together; then, ‘the 
plane, make the inner edges straight and even with _ 
each other. In order to prove that the blade is at right. 
angles with the stock, take a broad scale of brass, having 
its edges truly straight and parallel, a thing by no 
means difficult .to procure, and, first applying the 
square to one edge, draw a line across the scale with 
the dividing knife, and then, applying it to the other 
edge of the scale, with the same side uppermost, draw — 
another line extremely near the former. If the in 
are right, it is evident the two lines will be parallel to 
each other; but if they are inclined, half\their inclina-. 
tion is the error of the tool, which must be altered by 
grinding the edge of the steel-blade. It is almost’ un- 
necessary to observe, that the use of the square, in paz 
rallel dividing, is precisely the same as that of the in- 
dex in angular dividing. © 4 30h 
We omitted to describe the beam-co , for Bea 
the circular lines which limit the length of divisions, om pass 
account of that apparatus being well known; for the _ 
opposite reason, we now proceed to give a description 
of the gauge, (See Fig. 4.) an implement which  per- Div 
forms the same office in tracing parallel lines. It con- S0U8® 
sists of a brass beam A, about six or eight inches long; __ 
a socket B, of the same material, with a steel front to _., 
the left, which, sliding along the beam, may be set fast ~~ 
on any part.of it by the finger screw S on the upper 
side, and a tracer of tempered steel fixed ‘to the aniut : 
the beam by a wedge and screw. The tracer, has its 
point of action brought close to the inner edge, in or~ 
der that it may draw a line extremely near to the edge 
of the scale; its great length, as shewn in the Figure, 
being in no respect incommodious, is designed for the _ 
purpose that it should be lasting. The steel front of 
the socket extends in the line of its action about two 
inches, which enables the operator to keep the beam. 
without deviation at right angles to the edge of the 
scale ; and there is a projecting part in the front, of the 
same length, which, bearing upon the surface, kee 
the tracer perpendicular; this is discontinued in 
middle, for the purpose of admitting the tracer to be 
brought into contact with the front. The tracing 
point should be so adjusted as to be a very small quan- 
tity below the projecting part. . The end of the socket 
to the right is on every side chamfered to a thin edge, 
and the beam has divided upon its different sides many 
lines, suited to the most common work, such as draw= 
ing the parallel lines of diagonal scales, &c.' By drop- 
ping the dividing knife into these, pushing up the soc- 
ket into contact with it, and there fastening it, the ope 
rator places the steel front and the tracer at the 
distance for the performance of his work. In cases of 
less frequent occurrence, he clamps the socket -by trial, 
so as to make the tracer pass through points previously — 
laid down with the spring-dividers, a tool to be de« 
scribed presently. : 
- The process of dividing from yr line patterns 
being exactly similar to that from the dividing plate, it 
must be quite unnecessary to repeat it. We may, how- 
ever, observe, that in the former the’errors go undimi- 
nished to the work, while those of the dividing plate 
are contracted in the ratio of the radius of the plate — 
and work. Clockmakers pursue the contrary process ; 
they fix a small dividing plate upon the centre of their 
dials, and transfer the divisions outwards. It is not, 
however, now uncommon for them, in their very best 
AED AR ig hc St LYM RAP 
