TUTORIAL
Dividing and indexing hackspace-style
n machinist
terms, dividing
or indexing usually
means the methods
by which items are
created equally around
an object, often a circle. Common
examples are cutting the teeth of gear-
wheels, but it also can refer to drilling a
number of holes around a circular path, like a
cylinder head, or milling repeating flat sections to form
a geometric shape, such as a hexagonal bolt head.
There are numerous approaches and numerous
tools that can be used to help with dividing, the most
common one in a professional machine shop being
a dividing or indexing head. These are expensive
pieces of equipment for home users to purchase,
and are often too large to fit on smaller machines.
In this article, we are going look at alternatives –using hackspace-type
approaches to dividing
or indexing without a
dividing head.
This first alternate approach is
useful when, for example, we need
to drill a small number of holes around
a circle, often referred to as the pitch circle
diameter, or PCD. Some relatively simple
maths can be used to generate the X and Y axis
co-ordinates needed to drill these holes, and we can
mark out those positions on a workpiece, or we can
use the dials on a milling machine to move to these
positions and drill. We need to know how many holes
we require spaced around the circle, and we need
to know the radius of the circle. We then use two
similar equations to work out the X and the Y
co-ordinates of each hole location, relative to the
centre of the circle.I
Dividing and indexing
hackspace-style
Tools for dividing and indexing can be costly – let’s look at some
hackspace-type approaches to this common processYOU’LL NEED
Access to a
well-equipped
hackspace!Jo Hinchliffe
@concreted0gJo Hinchliffe is a
constant tinkerer and
is passionate about all
things DIY space. He
loves designing and
scratch-building both
model and high-power
rockets, and releases
the designs and
components as open
source. He also has a
shed full of lathes and
milling machines and
CNC kit!Figure 1
A laser-cut tool we
made to help mark
equidistant points
around the
circumference of
different sized tubes