Grade Application 202: Fiber Failures

In 202 you will gain an understanding of how fiber failures, classified as Checks, Splits, and Shake, affect lumber grades.

Syllabus

Grade Application 202: Checks

Checks are separations of the wood normally occurring across or through the rings of annual growth, and usually a result of seasoning.  The image to the right depicts allowable check sizes by grade based on the following chart.  (Remember: Click on the image to enlarge, then click anywhere outside the image to return to the course page)

 

Grade Limiting Provision
C Select Barely perceptible* on face and back
D Select Barely perceptible* on face.  Medium surface check on back
Finish** Small (not over 1/32″ wide and not over 4″ long)
Premium** Medium (not over 1/32″ wide and not over 10″ long)
Standard Surface and Through, ***1/4 length to a maximum of 3′
Industrial Not limited by grade

Barely Perceptible is defined as a check that is only visible when held at a favorable angle to the light.

** The reverse face of Finish and Premium shall permit checks equivalent to the face of Standard (1/4 the length to 3′).

*** Tips from the NELMA Inspector: Two quick methods for determining 1/4 the length: 1.) Multiply the length of the board in feet by 3; this will give you 1/4 the length in inches (L’ x 3 = 1/4 L in inches) or  2.) Simply divide the length of the board by 4 to get your answer in feet (L’ / 4 = L in Feet). The first method will bring simplicity to determining lengths on pieces that do not divide evenly.  You’ll find that either method will work in any situation, and you can decide which one works best for you.  

Important Note: Checks extending through the end of a piece are treated like a split and are limited to the coinciding split limitation for the grade. 

Grade Application 202: Splits

Splits are defined as a separation of the wood through the piece to the opposite or adjoining surface.  The length of a split is determined by taking a measurement of the split on each face and dividing the total measurement by two, see the formula below.  The limiting provisions by grade are indicated in the table below.  Click on the image to the right for a visual application of the limiting provisions by grade.  (Remember:  Click on the image to enlarge, then click anywhere outside the image to return to the course page). View the video for a demonstration on how to measure splits.

Average Length of a Split = (Face 1 length + Face 2 length)/2

 

Grade Limiting Provision
 C Select Splits are not permissible in C Select
 D Select Very Short, 1/2 the nominal width of the board
 Finish Very Short, 1/2 the nominal width of the board
 Premium Short, not to exceed the nominal width of the board
 Standard Medium, twice the nominal width, not to exceed ***1/6 the length
 Industrial Not to exceed 1/4 the length

***Tips from the NELMA Inspector: Previously you learned how to figure 1/4 the length. Well how about 1/6 of the length…any ideas? Don’t worry we’re here to help!  Here are a few quick ways to determine 1/6 the length: 1.) Multiply the length of the board in feet by 2; this will give you 1/6 the length in inches. ( L’ x 2 = 1/6 L in inches ), or 2.) Simply divide the length of the board in feet by six to get 1/6 the length in feet. ( L’ / 6 = 1/6 L in feet ).  The first method will work best for instances where the length of the board does not divide evenly.  You’ll find that either method will work in any situation, only you can decide which works best for you.      

 

Grade Application 202: Shake

Shake is a lengthwise separation of the wood which occurs between or through the rings of an annual growth. The limits to the amount of Shake permitted within each grade is provided in the table below.

 

Grade Limiting Provisions
C Select Barely perceptible* on face and back
D Select Barely perceptible* on face, light surface shake not over 1/4 the length on back
Finish Surface, Light; not to exceed 1/10 the length on the face, 1/4 the length on back
Premium Surface, Light; not to exceed 1/4 the length on the face and back.  Through Shake barely perceptible*
Standard Through, not to exceed ***1/3 the length
Industrial Not limited by grade

* Barely Perceptible is defined as Shake only visible when held at a favorable angle to the light. 

***Tips from the NELMA Inspector: Previously you learned how to figure 1/4 the length and 1/6 the length. Now we are going to show you an easy way to figure out 1/3 the length! To figure 1/3 the length you can 1.) Multiply the length of the board in feet by 4; this will give you 1/3 the length in inches (L’ x 4 = 1/3 the length in inches), or 2.)  Simply divide the length of the board in feet by 3 to get your answer in feet. (L’ / 3 = 1/3 L in feet). The first method works best for those instances where things do not divide evenly.  You’ll find that either method will work for any situation, but only you can decide which works best for you.

Important Note:  Shakes extending through the end of a piece are treated like splits and are limited to the coinciding split limitation for the grade.    

 

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