ns to
draw the curves in. In drawing these curves great exactitude is required
to properly find their centres; nothing looks worse in a drawing than an
unfair or uneven junction between curves and straight lines. To find the
location for these centres, set the compasses to the required radius for
the curve, and from the point or corner A draw the arcs _b_ and _c_,
from _c_ mark the arc _e_, and from _b_ the arc _d_, and where _d_ and
_e_ cross is the centre for the curve _f_.

[Illustration: Fig. 189.]

Similarly for the curve _h_, set the compasses on _i_ and mark the arc
_g_, and from the point where it crosses line 6, draw the curve _h_. In
inking in it is best to draw in all curves or arcs of circles first, and
the straight lines that join them afterward, because, if the straight
lines are drawn first, it is a difficult matter to alter the centres of
the curves to make them fall true, whereas, after the curves are drawn
it is an easy matter, if it should be necessary, to vary the line a
trifle, so as to make it join the curves correctly and fair. In inking
in these curves also, care must be taken not to draw them too short or
too long, as this would impair the appearance very much, as is shown in
Figure 187.

[Illustration: Fig. 190.]

[Illustration: Fig. 191.]

To draw the piece shown in Figure 188, the lines are drawn in the order
indicated by the letters in Figure 189, the example being given for
practice. It is well for the beginner to draw examples of common
objects, such as the hand hammer in Figure 190, or the chuck plate in
Figure 191, which afford good examples in the drawing of arcs and
circles.

In Figure 191 _a_ is a cap nut, and the order in which the same would be
pencilled in is indicated by the respective numerals. The circles 3 and
4 represent the thread.

[Illustration: Fig. 191 _a_.]

In Figure 192 is shown the pencilling for a link having the hubs on one
side only, so that a centre line is unnecessary on the edge view, as
all the lengths are derived from the top view, while the thickness of
the stem and height of the hubs may be measured from the line A. In
Figure 193 there are hubs (on both sides of the link) of unequal height,
hence a centre line is necessary in both views, and from this line all
measurements should be marked.

[Illustration: Fig. 192.]

[Illustration: Fig. 193.]

In Figure 194 are represented the pencil lines for a double eye or
knuckle joint, as it is sometime