Ordinary
drawing instruments, even of the higher grades, and costing a good deal
of money, are far from being satisfactory to a man who has the proper
idea of accuracy to be rated as a first-class mechanic. Ordinary
compasses are obstinate when we try to set them to the hundredth of an
inch; usually the points are dull and ill-shapen; if they make a
puncture in the paper it is unsightly.
Watchmakers have one advantage, however, because they can very easily
work over a cheap set of drawing instruments and make them even superior
to anything they can buy at the art stores. To illustrate, let us take a
cheap pair of brass or German-silver five-inch dividers and make them
over into needle points and "spring set." To do this the points are cut
off at the line _a a_, Fig 11, and a steel tube is gold-soldered on each
leg. The steel tube is made by taking a piece of steel wire which will
fit a No. 16 chuck of a Whitcomb lathe, and drilling a hole in the end
about one-fourth of an inch deep and about the size of a No.
Pages:
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37