The practice frequently adopted to poise a plain
balance is to file it with a half-round file on the inside, in order not
to show any detraction when looking at the outer edge of the rim. A
better and quicker plan is to place the balance in a split chuck, and
with a diamond or round-pointed tool scoop out a little piece of metal
as the balance revolves. In doing this, the spindle of the lathe is
turned by the hand grasping the pulley between the finger and thumb. The
so-called diamond and round-pointed tools are shown at _o o'_, Fig. 182.
The idea of this plan of reducing the weight of a balance is, one of the
tools _o_ is rested on the T-rest and pressed forward until a chip is
started and allowed to enter until sufficient metal is engaged, then, by
swinging down on the handle of the tool, the chip is taken out.
[Illustration: Fig. 182]
[Illustration: Fig. 183]
In placing a balance in a step chuck, the banking pin is caused to enter
one of the three slots in the chuck, so as not to be bent down on to the
rim of the balance.
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