The lathe and mill are traditional
tools for constructing precision
parts. A lathe is used to rotate a part
against a cutting tool. It is typically
used to contour round or cylindrical
material, like creating threads on a rod.
A mill is like a vertical drill press.
Instead of a cutting bit that just goes up
and down, the work piece itself on a
mill can be moved horizontally and
vertically. This allows the mill to produce
complex shapes instead of just holes.
These tools are not particularly
common in the robot workshop, but —
if you’re interested in taking your robot
building to the next level — you should
seriously consider getting one. If you
want to go even further, think about
automating the lathe or mill with your
computer. CNC tools (CNC stands for
computer numerical control) let you
automate the fabrication process to a
great extent. Rather than being operated
by hand cranks, the tool is operated by
motors, which are connected to a
desktop computer — usually a basic PC
running Windows or DOS.
In the typical scenario, software on
the PC translates a two-dimensional
(more rarely, a three-dimensional)
picture into a set of data points, so that
it can move the motors in a pre-defined
by Gordon McComb
A third type of machine is the CNC
router. It combines a high-speed
cutting tool — like a wood router — and
a mechanism that moves the router in
the X, Y, and Z axes. This movement is
likewise managed by a computer. The
router is the ideal tool for creating
robot bases. With this tool, you can
drill holes of almost any size (down to
the diameter of the routing bit, which
can be as small as 1/16”). You can
then, under precise computer control,
cut out the shape of the base to
produce the final piece.
Entry Costs for CNC
For building personal robots, the
smaller “desktop” mill, lathe, and
router are usually more than adequate.
You don’t need — and probably don’t
want — the large, industrial versions of
these machines. Desktop tools can
handle pieces of the typical size found
in personal robots and, because they
are smaller, they are less expensive and
easier to use.
The typical starting price for the
better-made, non-CNC tool is $500.00.
As you add computer control, price
climbs to $1,500.00 and even into the
$2,000.00 range. A good desktop CNC
router is about $3,000.00. Software is
not always included in these prices and
it can add $300.00 to $1,000.00 (and
more) to the price.
If you’re interested in acquiring a
desktop mill, lathe, or CNC router,
you’re well advised to get information
on as many of them as possible. In the
resources listing that follows, you’ll find
several informational sites that discuss
desktop lathes and mills. Also included
are numerous sites that talk about
retrofitting a manual lathe or mill for
CNC and building your own CNC router
from the ground up.
Consider that not all desktop tools
are created equally. Some are designed
for garage shop tinkerers on a budget.
They’re fine for working with lightweight materials — like soft plastics and
thin woods — but don’t try to use them
to produce highly accurate, complex
shapes from stainless steel. Price goes
up based on accuracy, power, and size,
so plan your purchase accordingly. If
you need to work with pieces up to 20
inches, don’t settle for a machine with a
maximum cutting size of just 18 inches.
One way to save money on a
desktop mill or lathe is to purchase it
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