TUTORIAL
Dividing and indexing hackspace-style
used for dividing purposes. It consists of a circular
worktable which is rotated by a gear and worm-gear
arrangement attached to a winding handle. It’s a
common project for machinists to convert rotary
tables into forms of dividing head by adding dividing
plates but, even in its standard form, the rotary table
can be useful for dividing. In Figure 4,we can see that
we have used the rotary table and a vice to create a
circle of 15 equidistantly placed holes around a pitch
diameter. Simply dialling the table around 24 degrees
per index using the graduated dial moves the
workpiece to the next position, and a grub-screw on
the table acts as a lock to clamp the table while
performing the drilling operations.
Using the lathe to divide can be of use, and one job
we wanted to create was a dial handle with graduated
markings every 36 degrees (so ten marks in a full
rotation) – Figure 5. This dial will eventually be part
of an assembly that moves the spindle forwards
and backwards at a rate of 1 mm per complete
revolution. So, marking it with ten marks means
each mark equates to 0.1 of a mm movement. We
had heard anecdotes of people using a magnetic
digital protractor tool to rotate the chuck by a known
amount. The digital protractors are available for less
than £15 online, and have a magnetic base so can be
attached to ferrous objects. They can be set into a
mode where they can be zeroed, and therefore we
can repeatedly use them to rotate objects by a known
amount. To create this crude but effective marked dial
handle, we placed the workpiece in the lathe chuck
with the lathe unplugged, and locked the spindle in
place. We then used a sharp tool in the tool holder to
mark a line into the workpiece by pushing it into theThere are some tools that sit in the midpoint between
no tools and a dividing head for the workshop that can
be useful on the milling machine to create divisions.
The spin indexer is a relatively cheap tool, and we
picked up our example for around £60. A spin indexer
is a device which can clamp a workpiece in a collet,
and the collet can be rotated by a known amount. The
modern spin indexer has a graduated dial with the
numbers 0–36 each representing 10 degrees of a
circle. On the body of the spin indexer are ten holes
labelled from 0 to 9, into which a pin can be located.
Rotating the collet spindle and aligning a number to
the arrow gives us the crude position to the nearest
ten degrees, and then we place the pin in the hole for
the single digit and move the spindle until the pin
engages. This means we can accurately position the
spindle to a single degree, making it possible to index
a piece through any combination of divisions of 360
degrees. In the images, you can see that we have
created a hexagonal workpiece by indexing some
round brass bar stock through 60 degree steps, and
milling a flat section in each position.ALMOST THERE
Figure 3
Using a 3D-printed
press fit collar on a
piece of brass bar to
perform eight
equidistant milling
operations around
its circumference