It consists of a base plate on which are mounted two standards, high enough to admit the largest size disc required.
Each standard is fitted with two steel pins, and on each pin is mounted a
steel wheel turned to a cone on periphery. These wheels rotate on ball bearings
on the pins.
A set of mandrels of the same size as the standard pump spindles are provided,
they having keyways cut in them just as in the spindles, and two grooves
are turned near the ends to rest on the conical wheels.
This apparatus is extremely sensitive, so much so that if the mandrel only
is placed on the wheels, the keyway comes instantly to the top.
To balance a disc, it is first accurately turned all over wherever the turning
tool can get; it is then keyed on the mandrel, taking care to use a key of the
exact size that will be used in the finished pump. Placing mandrel and disc
in machine any out of balance at once brings the heavy aide to the bottom,
and to correct the arms and inside must be dressed till the disc has no " heavy
side."
The machine should be placed on a solid foundation where there is no
vibration.