Slope of grain

How to process lumber to achieve a given slope of grain. March 28, 2001

I have a request for 1" x 1.5" x 26" pieces of lumber with grain deviation of not more than 1" per 12 inches.

In a plain sawn board the grain on the top of the board may appear to deviate a lot, but the grain on the edge does not. What is the conventional measure?

Forum Responses
What he or she is asking for is called "slope of grain", to not exceed 1" every 12". That should be very easy to mill. It depends on the type of wood. Softwood or hardwood can be sawn parallel to the bark or parallel with the pith. One way will give you straight grain and the other might give you grain that slopes too much to meet his needs.

The grain is not discovered by looking at an annual ring in sawn wood. The grain can actually be spiral or at an angle, crossing the rings. The 1:12 slope of grain (SOG) is a standard specification for construction softwood lumber and for splits in hardwood lumber. Grain is measured by looking at the angle of a split (if any) or by using a flexible stylus that has a point that will follow the grain. Ask any softwood grader.

Gene Wengert, forum technical advisor

Can you recommend a good book that describes this stylus method of determining SOG?

I think the folks at Renewable Resource Associates, Inc. can help, or try the SPIB or Timber Prod Insp. Or search on the web for Southern Pine Inspection Bureau or Timber Products Inspection.

An additional comment: When grading, the grain means one thing; there are actually 7 or 8 definitions of grain that can be applied at different times and in different situations (tight grain, longitudinal grain, curly grain, along the grain, coarse grain, etc.).

Gene Wengert, forum technical advisor