Page 64 - Making things move_ DIY mechanisms for inventors, hobbyists, and artists

Chapter 2 Materials: How to Choose and Where to Find Them 45

In general, harder woods are stronger, but more difficult to work with. Soft woods like
balsa are very light and easy to work with, but also very weak and split easily. Wood
tends to split along the grain (that’s why those disposable wooden chopsticks pull
apart so easily).

Composite woods like plywood, medium-density fiberboard (MDF), chipboard, oriented
strand board (OSB), particle board, and Masonite are popular due to their low cost
and availability. All are combinations of wood chips or particles and binding agents.

• Plywood is made of alternating layers of large wood chips at right angles to
each other that are held together with glue, so it is stronger than the sum of
its parts and tends not to split like pure woods. Aircraft-quality plywood,
available from hobby stores, is higher quality than home-construction plywood.
• MDF is made with fine sawdust combined with a wax and resin binder, and
formed under pressure, which makes it stronger and denser than plywood,
but also heavy.
• Thin Masonite is very popular to use with laser cutters. It is more environmentally
friendly than some of the other composites because it is made from natural
materials and doesn’t used formaldehyde-based resins to bond the wood
particles.
• Bamboo is even more environmentally friendly. Because it grows so fast, it’s
easily renewable. A few companies make bamboo plywood (try www.plyboo.com
for a sample), but it may be a few years before prices come down and bamboo
becomes more popular with hobbyists.

Natural woods have a wide range of properties as well. Maple, cherry, and oak are
very hard. Spruce and balsa are very soft. They also come in a variety of shapes and
sizes, from sheets to more common structural forms like 2 × 4 boards.

The lumber section of your local home-improvement store, arts-and-crafts stores, and
hobby stores are good places to find wood materials. Look for wood with few or small
knots, dings, or cracks. Look down the board length to check for warp, and avoid wet
boards. You may also find scrap wood outside these stores, and some of that might
be suitable for your projects.