Page 218 - Making things move_ DIY mechanisms for inventors, hobbyists, and artists

196 Making Things Move

Thrust Bearings
Thrust bearings (see Figure 7-7) support axial loads, which are parallel to and ideally in
line with a shaft. These can have rolling elements or just be washers made of slippery
materials. If you’ve ever been to a restaurant with a rotating center turntable, known
as a lazy Susan, you’ve encountered a thrust bearing. This turntable allows a lot of
heavy food to be stacked on it while still allowing you to spin it easily. You can also
find thrust bearings in rotating bar stools, chairs, and on a smaller scale, in rotating
spice racks. See Projects 10-1 and 10-2 in Chapter 10 for examples of how to use
these bearings.

Thrust Ball and Roller Bearings
Thrust ball and roller bearings are similar to radial ball and roller bearings with the
components reversed to handle axial loads. The vocabulary is mostly the same, with
these differences:

• Outer diameter The outer diameter on thrust bearings shouldn’t touch
anything, so size it accordingly.
• Inner diameter Unlike radial bearings, the inner diameter should not be a
tight fit on the shaft. There should be clearance between the inner diameter
and shaft so they rotate freely relative to each other, but not so much slop
that the shaft has room to wiggle around.
• Cage Although optional in radial bearings, thrust bearings always have
cages to separate and contain the rolling elements.

FIGURE 7-7 Thrust bearings and bushings (credit: McMaster-Carr)