Flatsawn, riftsawn and quartersawn ?

In manufacturing on May 5, 2014 at 2:44 pm

When you are shopping for lumber, you’ll find that grain patterns will vary from board to board and often even within a single board. The board’s original location within the log, and how the log was converted into lumber, will dictate this grain direction.
LogGrain Illustration

Flatsawn boards typically display a cathedral pattern. A riftsawn board will have very straight grain and a quartersawn board has a straight grain with lots of ray flecks.

Endgrain

The connection between the growth rings on the end grain and the face of the board is clearly visible. This board would yield a handsome cathedral figure board on the left and a riftsawn board on the right.

The following lesson will teach you to “read” grain direction and differentiate between the three principal grain orientations.

Sawing a log into boards is called conversion. Most logs are converted to yield the maximum number of board feet by a method called plainsawn. They are sawn into slices like a loaf of bread, but down the length. A cylindrical log cut this way yields boards that look much alike on the surface. For instance, if same-thickness boards are cut from two logs of the same species and diameter, the 10th boards from each log will look generally alike, as will the 20th boards.

Wood harvested this way falls into one of three groups: flatsawn, riftsawn, and quartersawn. Each group is defined by the angle at which the annual rings on the end grain meets the surface of the board. A quartersawn board has rings between 90° and 70° to the surface, and a riftsawn board has rings between 70° and 45° to the surface. When all the rings form a curving horizontal to the surface – less than 45° – the board is flatsawn.

The first and last few boards from the log will be flatsawn, while the middle boards will be primarily quartersawn. Nowhere will you find a wholly riftsawn board: it will be part of one of the other two groups. Indeed, a board from the middle of a large diameter log will be made up of all three groups. Clearly, nature doesn’t precisely honor our neat description, but the terms work well enough. A flatsawn board exhibits strong cathedral grain. Quartersawn boards have straight grain with the rays breaking the surface as very noticeable large smudges. Riftsawn is straight grain, absent the flashes of ray tissue. The rays are there, but are more noticeable on the end grain than the flat surface.

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