WOODWORKING
Chapter 12True Size
Introduction:
In the last chapter we discussed how boards are identified by their first, middle, and last name (the thickness,
width, and length). We might call this their formal name. However, just like people, names don’t always define who
we actually are. Your name might mean “Crazy Person,” or “Fire Tree,” but that doesn’t tell us who you are.
Lumber names are just like that. The name of a board doesn’t tell us the whole truth about the board. It is simply the
way it is identified. So, if your name means “Angry Person,” you might actually be very nice. The same is true about
lumber. A board might be named 2x4, but that doesn’t tell us the true nature of that board. In other words, a 2x4 is
not exactly two inches thick and four inches wide. Let’s see why.Milled Lumber:
After a tree is cut down and turned into a log, it is then sent through a saw to be cut into boards. When the log is
first cut, the boards are cut to the exact inch through a process called rough sawing. A 2x4, then, is cut out of the log
exactly two inches thick and four inches wide. That is its rough sawn size. Likewise, the rough sawn size of a 1x6 is
one inch thick and six inches wide, and the rough sawn size of a 4x8 is four inches thick and eight inches wide. But
these are not the sizes they come to us.
At the lumberyard, after lumber has been rough sawn
from the log it is also dried and planed. As you can
imagine, the rough sawn boards cut from logs are not all
going to be the exact same size. They are, after all, rough.
They need to be smoothed and the corners need to be
rounded. The planing process fixes this.
A wood planer is a large machine with round drums
inside. The bottom drum turns and rolls lumber through a
cutter. The top drum, or cutter, contains blades for cutting
or shaving the wood. By adjusting the top drum, the
millworker can determine the final size of the board.
During this shaving process, the rough sawn lumber
changes from rough sawn to a true size. A 2x4, then, is no
longer two inches by four inches. It is smaller. This
planing process allows boards around the world to be cut
the exact size, which makes building homes and furniture
a whole lot easier.Actual Size:
The standard that has been set for lumber sizes determines how much is shaved off of the board. 2x4s, for
instance, have ½" shaved off the thickness and the width. So, the true size of a 2x4 is actually 1 ½” x 3 ½”. But isn’t
calling it a 2x4 so much easier to say?
As you can see, the formal name of a board and the truth about that board are different. Look at the chart below,
and see the difference between the two.Formal Name Actual Size Formal Name Actual Size Formal Name Actual Size
1x2 ¾ x 1 ½ 2x2 1 ½ x 1 ½
1x3 ¾ x 2 ½ 2x3 1 ½ x 2 ½
1x4 ¾ x 3 ½ 2x4 1 ½ x 3 ½ 4x4 3 ½ x 3 ½
1x6 ¾ x 5 ½ 2x6 1 ½ x 5 ½ 4x6 3 ½ x 5 ½
1x8 ¾ x 7 ¼ 2x8 1 ½ x 7 ¼ 4x8 3 ½x 7 ¼
1x10 ¾ x 9 ¼ 2x10 1 ½ x 9 ¼ 4x10 3 ½x 9 ¼
1x12 ¾ x 11 ¼ 2x12 1 ½ x 11 ¼ 4x12 3 ½x 11 ¼