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In-Depth Information
Figure 6-8. Part M with the drill hole locations marked using the actual size plans
Take a look at Figure 6-9. It contains another portion of the building plans, but this one shows two
new items: a channel to be cut into the piece (for inserting an Allen wrench later to adjust the coupling
that will be fastened to the motor shaft) and four counterbore holes drilled into the face of Part M. The
large hole in the center will provide room for this coupling.
So what is a coupling and why is it needed? The motor shaft will need to turn a lead screw (a long
screw without stub ends). There are two challenges for the motor to turn the lead screw. First, the shaft
and the screw are two separate components and something needs to connect the two while allowing
some flexibility for slight misalignment. Second, the shaft and the screw are two different sizes in this
machine. A coupling is simply a small assembly that solves both of these problems with a hole on each
end and a rubber component at the midpoint for flexibility. This coupling has a set screw to tighten
against the shaft of the motor and the lead screw. The set screw for the shaft of the motor will be
adjustable through this slot created in this part. (We'll cover the coupling during the assembly portion of
the project later in Chapter 13.)
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