Page 251 - Making things move_ DIY mechanisms for inventors, hobbyists, and artists

Chapter 7 Bearings, Couplers, Gears, Screws, and Springs 229

FIGURE 7-41 An aluminum sprocket and 1/4 in chain mounted to a servo motor (credit:
ServoCity)

Power Screws

We talked about using screws as simple machines in Chapter 1, and screws as
fasteners in Chapter 3. Power screws get their name from their intended use. Their
geometry allows them to lift heavy loads, as well as precisely position anything riding
on them.
There are a couple kinds of power screws: threaded rods and ball screws. You may
have encountered common threaded rods, sometimes referred to as all-thread. These
are designed for fastening things that are thick or far apart, and look just like longer
versions of fastening screws. Although not designed to be used as power screws, they
do the job well in MakerBot’s CupCake CNC, where high precision and heavy lifting
are not the main concerns. Acme threaded rods use a special geometry thread
designed to lift heavy loads more efficiently.