Page 83 - Making things move_ DIY mechanisms for inventors, hobbyists, and artists

64 Making Things Move

3. Act as a spacer to avoid stressing the tiny curved section directly under the
screw head

4. Indicate proper tightness of the bolt—when the washer is snug and stops
spinning, it’s time to stop turning the screwdriver

For a well-designed bolted joint, use spring-lock washers in addition to standard
washers (see Figure 3-3). The job of the spring-lock washer is to keep the joint tight
even if the screw vibrates loose. When a spring-lock washer is compressed, it looks
just like a fat washer with a gap in it, or a C shape. However, if the screw begins to
loosen—either through wear and tear or vibration—the spring-lock washer springs up
as the C shape untwists to fill the tiny gap created.

Nails and Staples

Nails are more permanent than screws but can still be removed relatively easily. The
following are types commonly used in projects:

• Double-headed nails are good to hold something together temporarily and
much easier to remove than common nails.
• Finishing nails have small heads designed to sink into the material, so never
use these if there’s a chance you’ll need to take one out.
• Small nails, called upholstery tacks, can secure fabric stretched over a frame,
as used in furniture designs.

Nail guns make short work of this job. Similarly, a staple gun, or just a normal stapler
opened up, makes short work of stapling material together to temporarily secure it.

Nails and staples are often the lazy way out of designing good, nonpermanent joints.
I recommend using them only for temporary holding or early prototyping stages, not
for general use. Removing wrongly installed nails and screws usually renders them
unusable, damages your base material, forces you to line up your pieces again, and
wastes more nails or screws. This cycle can get repetitive and tedious. Try designing
your projects to use nuts and bolts from the early stages, and resort to nails and
staples only if you have no other choice.