Civil Engineering Reference
In-Depth Information
Fig. 10.3. Dividing heads are normally mounted to the left of the spindle and you turn
the handle clockwise.
DISKS OR DIVISION PLATES
You can attach round disks (division plates) to the worm drive mechanism.
These disks contain varying numbers of holes all set equally around the disk.
Each disk can have several hole circles, each with different numbers of holes.
The number of holes usually increases in number from the inner circle to the
outer circle.
The disk is fixed to the main body, and a handle with a moveable plunger is
fixed to the worm gear shaft so you can rotate the spindle through the worm
and wheel. The plunger can slide in and out of the drilled holes on the divi-
sion plate. Also mounted on the dividing head is a pair of sector plates. These
plates can be rotated around the worm spindle. The sector plates can be set
at various hole positions apart and are used as a guide as to how many holes
the plunger can be rotated.
The number of holes
The number of holes the plunger should be moved is always plus one hole.
This is because the plunger itself takes up a hole. For example, say you need
to move the handle through 20 holes. As the plunger takes up one hole, if you
move the plunger 20 holes, the plunger will only move 19 holes as it will be in
the first and last hole; so you need to add an extra hole to the sector plates
