Page 102 - Robot Builder's Bonanza

PLANKS OR PLY 71

Metric Inch Plies
6.0 mm 2.3622 12
8.0 mm 3.1496 16
12.0 mm 4.7244 24

3.0 mm = approx. 1/8″
6.0 mm = approx. 1/4″
12.0 mm = approx. 1/2″

Don’t confuse hardwood plywood with hardboard. Hardboard is a manufactured product,
G usually made by munching up sawdust into tiny pieces, then fusing them together under high
pressure. See the section “Medium Density Fiberboard” for a kind of hardboard usable in
robotics.

USING PLANKING

An alternative to plywood is planking. Hardwood planking— stuff like oak or birch— tends to
be very heavy and much harder to work with. Opt for Douglas fir or pine. These softer woods
are okay for smaller robots, and they are easier to cut and drill.
Plank lumber is available in widths of no more than 12″ or 15″ wide, so you must take this
into consideration when designing your robot platform. Be especially wary of warpage and
moisture content when using plank lumber. Borrow a carpenter’s square, and check the
squareness and levelness of the lumber in every possible direction. Reject any piece that isn’t
flat and square.
Wood with excessive moisture may bow and bend as it dries, causing cracks and warpage.
These can be devastating in a robot you’ve just completed and perfected. Buy only seasoned
lumber stored inside the lumberyard, not outside. Watch for green specks or grains— these
indicate trapped moisture.

COMMON PLANKING DIMENSIONS
Plank lumber is milled in common dimensions. Unless otherwise noted, the finished milled
dimension is less than the stated size, because of saw kerf. When you buy two- by- four lumber,
for example, you’re really only getting 1-1/2″ 3-1/2″.

Dimension Thickness Width
1 4 3/4″ 3-1/2″
2 4 1-1/2″ 3-1/2″
1 6 3/4″ 5-1/2″
2 6 1-1/2″ 5-1/2″
1 8 3/4″ 7-1/4″
1 10 3/4″ 9-1/4″
1 12 3/4″ 11-1/4″

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