A knot is a portion of a branch or limb that has become incorporated in a piece of lumber. Knots are classified as to form size, quality and occurrence [Standard Grading Rules for Northeastern Lumber para. 718.0].
Characteristics 101: Knots and Wane
In Characteristics 101 you will be learning to identify knots. Knots, in all their forms are arguably Eastern White Pine’s most recognizable and defining characteristic. Your ability to quickly identify knots is your first step into becoming a quality grader.
Syllabus
101: What is a Knot?
101: Red Knot
A red knot it one that results from a live branch growth in a tree that is intergrown with the surrounding wood. [Standard Grading Rules for Northeastern Lumber para. 718.0 (a)].
101: Black (encased) Knot
A black knot is one that results from a dead branch which the wood growth of the tree has surrounded. [Standard Grading Rules for Northeastern Lumber para. 718.0 (b)].
101: Spike Knot
A spike knot is produced when the limb is cut either lengthwise or diagonally. [Standard Grading Rules for Northeastern Lumber para. 718.0 (e)].
101: Knot Sizes
There are four general classifications for knot sizes. [Standard Grading Rules for Northeastern Lumber para. 718.00 (f)-(i)]. These are each directly related to lumber grade as you will learn in later coursework.
Pin – a pin knot is not over 1/2”
Small – a small knot is not over 3/4”
Medium – a medium knot is not over 1-1/2”
Large – a large is over 1-1/2”
101: Sound Knot
A Sound Knot contains no decay. [Standard Grading Rules for Northeastern Lumber para. 718.0 (j)].
101: Unsound Knot
An Unsound Knot contains decay. [Standard Grading Rules for Northeastern Lumber para. 718.0 (m)].
101: Tight, Loose and Fixed Knots
Tight Knot – a knot so fixed by growth, shape or position that it retains its place in the piece.
[Standard Grading Rules for Northeastern Lumber para. 718.0 (o)].
Loose Knot – a knot not held tightly in place by growth, shape or position. [Standard Grading Rules for Northeastern Lumber para. 718.0 (s)].
Fixed Knot – a knot that will retain its place in dry lumber under ordinary circumstances, but is movable under pressure (commonly referred to as a clicker) though not easily pushed out. [Standard Grading Rules for Northeastern Lumber para. 718.0 (t)]. These are commonly referred to as “a clicker.”
101: Wane
Wane is the appearance of bark or lack of wood from any cause, except eased edges, on the edge or corner of a piece of lumber. [Standard Grading Rules for Northeastern Lumber para. 750.0]
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