dimensions can be measured accurately, it is possible to set the
gage to a given angle within very close limits. Moreover, if a record of
the three dimensions is kept, the exact setting of the gage can be
reproduced quickly at any time. The following rules may be used for
adjusting a gage of this type.

[Illustration: Fig. 16. Disk Gage for Accurate Measurement of Angles and
Tapers]

=To Find Center Distance for a Given Taper.=--When the taper, in inches
per foot, is given, to determine center distance _C_. _Rule:_ Divide the
taper by 24 and find the angle corresponding to the quotient in a table
of tangents; then find the sine corresponding to this angle and divide
the difference between the disk diameters by twice the sine.

_Example:_ Gage is to be set to 3/4 inch per foot, and disk diameters
are 1.25 and 1.5 inch, respectively. Find the required center distance
for the disks.

0.75
---- = 0.03125.
24

The angle whose tangent is 0.03125 equals 1 degree 47.4 minutes; sin 1 deg.
47.4' = 0.03123; 1.50 - 1.25 = 0.25 inch;

0.25
----------- = 4.002 inches = center distance C.
2 x 0.03123

=To Find Center Distance for a Given Angle.=--When straight-edges must
be set to a given angle [alpha], to determine center distance _C_
between disks of known diameter. _Rule:_ Find the sine of half the angle
[alpha] in a table of sines; divide the difference between the disk
diameters by double this sine.

_Example:_ If an angle [alpha] of 20 degrees is required, and the disks
are 1 and 3 inches in diameter, respectively, find the required center
distance _C_.

20
---- = 10 degrees; sin 10 deg. = 0.17365;
2

3 - 1
----------- = 5.759 inches = center distance _C_.
2 x 0.17365

=To Find Angle for Given Taper per Foot.=--When the taper in inches per
foot is known, and the corresponding angle [alpha] is required. _Rule:_
Divide the taper in inches per foot by 24; find the angle corresponding
to the quotient, in a table of tangents, and double this angle.

_Example:_ What angle [alpha] is equivalent to a taper of 1-1/2 inch per
foot?

1.5
--- = 0.0625.
24

The angle whose tangent is 0.0625 equals 3 degrees 35 minutes, nearly;
then, 3 deg. 35 min. x 2 = 7 deg. 10 min.

=To Find Angle for Given Disk Dimensions.=--When the diameters of the
large and small disks and the center distance are given, to determine
the angle [alpha]. _Rule:_ Divide the difference between the disk
diame