| Wood Basics |
In the USA,
there are over 1,000 species of trees. Of these, only about 100 are used
for constructing and manufacturing wood products. From this group, it's
best to pick the ones that are easiest to work with and most appealing
to you.
There are
basically two kinds of wood from which to choose— hardwoods and softwoods.
In addition, there are certain characteristics that are common in all
wood types. Here are some common terms and definitions you should know:
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HARDWOODS
These are the trees that lose their leaves in the fall (deciduous).
Among an abundant variety, only 200 are plentiful and pliable
enough for woodworking. Much like our skin, hardwoods have microscopic
pores on the surface. The size of these pores determines the grain
pattern and texture. Because of this, hardwoods are classified
by pore openings as either: Closed Grained (smaller pores) —
Most popular examples: cherry and maple; Ring Porous (larger pores)
— Most popular examples: oak, ash or poplar.
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SOFTWOODS
Softwoods come from "evergreen" trees (coniferous). Only 25 percent
of all softwoods are used in woodworking. All softwoods have a
closed grain (small pores) that is not very noticeable in the
finished product. The most popular softwoods are cedar, fir, pine
and spruce.
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DENSITY
Heavy woods like oak are identified by their weight and tight
grain pattern, and resist wear, dents and scratches better than
softwoods.
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TEXTURE
This is the wood property that determines the condition of the
surface and stability. It plays an important role in deciding
how a wood can be finished.
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DEFECTS
Defects in wood are natural and are appreciated by many woodworkers
for the unique character they contribute.
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COLOR
Color contributes to the personality of wood. For example, red
cedar will give you a very different look and character than white
pine.
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GRAIN
Grain
is the most well-known wood characteristic. Grain pertains to
the wood-cell fibers' orientation. The project you are undertaking
dictates the most
suitable type
of grain.
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GRADES
Lumber grades are determined by the number, location and size
of defects in the board, not its strength. The clearer the wood,
the higher the grade.
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STABILITY
This is the wood's ability not to shrink or expand before or after
it has been worked.
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DURABILITY
Durable woods better resist excess moisture and exposure to the
earth, where there's a greater chance of decay. Remember, no wood
will decay if it's kept dry.
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| A Closer Look at Wood Grain |
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Two
boards of the same species can look very different. Each tree has
its own grain pattern. This is the direction in which the wood cell
fibers grow. These variances in grain direction can have a significant
impact on your project.
The
grain direction is important to consider when building either structural
projects or decorative projects such as furniture or crafts. For
instance, when working on a structural application, a straight-grained
board is generally the strongest. In more decorative projects, grain
with varying characteristics can add beauty and personality to the
project.
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There
are six general types of grain:
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Diagonal
Grain
When a straight-grained log is not sawn along its vertical axis, diagonal
grain is the result. |
Spiral
Grain
When trees grow twisted, spiral-grained logs and subsequent boards
are produced. Fibers follow a spiral course with a twist that is either
left- or right-handed. |
Straight
Grain
The board's fibers run approximately parallel with the vertical axis
of the log from which it originated. |
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Wavy
Grain
This type of grain results when the direction of wood fibers has constantly
changed. |
Irregular
Grain
Boards of this type have fibers at directions that are varying and
irregular from the log's vertical axis (for example: fibers around
knots). |
Interlocked
Grain
Boards with this grain result from trees whose fibers lined up in
opposite directions in each growth year. |
Grain pattern
density determines strength. As you'd expect, a piece of lumber with a
tight pattern is stronger than one with a loose grain pattern. And when
building, a board's strength is maximized when other pieces run across
the grain pattern — not parallel to it.
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| Making the Grade |
When you
are choosing lumber, do you know what the stamp on the wood actually means?
Fear not! We've deciphered those hieroglyphics for you. So the next time
you go to the lumber yard, you'll sound like a pro.
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| Grades of Hardwoods |
Grading designation depends on the number of defects in a given length
and width of hardwood boards. As with softwoods, a lower grade can be
perfectly acceptable, depending on placement and usage. Hardwoods are
graded by the National Hardwood Lumber Association. Here's a chart to
help explain the grading system. Grades are listed from highest to lowest.
| Grade
Name
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Abbreviation
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Minimum
Board Size
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%
Usable Material On One Face
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| Firsts
and Seconds
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FAS
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6"
x 8'
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83
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| Select
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Sel
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4"
x 6'
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83
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| #1
Common
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#1
Com
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3"
x 4'
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66
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| #2
Common
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#2
Com
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3"
x 4'
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50
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There are grades below #2 Common, but they are typically not suitable
for woodworking.
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| Grades of Softwoods |
Softwoods are divided into two categories: dimensional lumber, with a
grade based on strength, and appearance boards, which are typically used
for woodworking projects. Grading of softwoods is overseen by a number
of different agencies, so you will be more likely to find some variations
in terminology. Grades listed here are from highest to lowest.
| Grade |
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What It Means |
| C
Select |
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Almost
completely clear of defects. Widely used for interior trim and cabinets. |
| D
Select |
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Fine
appearance, similar to C Select. May have dime-sized knots. |
| 1
Common |
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Best
material for high quality pine with a knotty look. Knots will be tight,
meaning they won't fall out and are generally small. |
| 2
Common |
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Tight
knots, but larger than found in 1 Common. Often used for paneling
and shelving. Very suitable for general woodworking projects. |
| 3
Common |
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Knots
larger than in 2 Common. Also used for paneling and shelving, but
especially well-suited for fences, boxes, and crates. |
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| Lumber Grading Stamp |
While lumber of the same species and size is still at the mill, it
is designated and separated by grade. It is then identified by a stamp
and often inventoried by its grade and species. When selecting wood, be
sure you look for its grading stamp because different lumberyards sometimes
use different names for the same grade. (And remember, if you are having
trouble figuring it all out, ask for help.) Grade designations depend
on particular defects such as knots or wane. Keep your project final results
in mind when selecting the grade of wood. Grade does not indicate consistency
of color or grain patterns.
Manufacturer:
Mill's number, name, or symbol. (ex. 12)
Certification
mark: Symbol of agency providing quality-control supervision. (ex.
WWP®)
Grade:
Often abbreviated. 1 Common shown. (ex. 1COM)
Moisture
content (MC:) Abbreviation for MC when board surfaced. MC 15 is 15
percent or less;
KD or S-DRY is 19 percent or less; S-GRN is green wood with more than
19 percent MC. (Ex. S-DRY)
Species
mark: Symbol or abbreviation for types of tree. Example shown is Ponderosa
pine. (Ex. PP)
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