Grade Application 205: Manufacturing Defects

In 205, you will learn how the various defects from the manufacturing process can be applied to the NELMA grades. Manufacturing imperfections, though allowed in the grades, are not typically desired by the end user.  A grader should notify the planer operator or manager when any of these imperfections are occurring frequently.

Syllabus

Grade Application 205: Torn Grain

 

Torn Grain is an irregularity in the surface of the piece where wood has been torn or broken out by surfacing.  The limitations for each grade are listed below.

 

Grade Allowable Depth
C Select Not Permitted within Grade
D Select Very Light (up to 1/64” depth)
Finish Very Light (up to 1/64” depth) not over 5% of face
Premium Medium (up to 1/16″ depth) not over 10% of face
Standard Medium (up to 1/16” depth)
Industrial Not Limited by Grade

 

Grade Application 205: Raised Grain

Raised Grain is a roughened condition of the surface of dressed lumber in which the hard summerwood is raised above the softer springwood, but not torn loose from it.  The limitations by grade for this defect are listed below.

 

Grade Allowable Depth
C Select Very Light (not over 1/64″)
D Select Very Light (not over 1/64″)
Finish Very Light (not over 1/64″)
Premium Light (not over 1/32″)
Standard Light (not over 1/32″)
Industrial Not Limited by Grade

 

Grade Application 205: Mismatch

Mismatch is an uneven fit in worked lumber when adjoining pieces do not meet tightly at all points of contact or when the surface of adjoining pieces are not in the same plane.  See the table below for grade limitations.

 

Grade Allowable Mismatch
C Select Very Light (not over 1/64″)
D Select Very Light (not over 1/64″)
Finish Very Light (not over 1/64″)
Premium Very Light (not over 1/64″)
Standard Very Light (not over 1/64″)
Industrial Not Limited by Grade

 

Grade Application 205: Skips

 

Skips are areas on a piece that failed to surface clean.  The limitations by grade are listed below which include the terms “Hit and Miss” and “Hit or Miss”.  For instructions regarding these terms see the video within this section.

 

Grade Allowable Skip
C Select One Light (not over 1/32″) 2′ Skip per each 8’ of length on reverse face.
D Select Hit and Miss on reverse face OR one edge
Finish Hit and Miss (not over 1/16″) on reverse face OR Light skip (not over 1/32″) on one edge not exceeding 1/4 the length.
Premium Hit and Miss (not over 1/16″) on reverse face or on one edge
Standard Hit and Miss (not over 1/16″) on reverse face; one edge may be 1/16” (Medum) scant full length or 1/8” (Heavy) scant for half the length
Industrial Hit or Miss (not over 1/16″) or a Heavy (not over 1/8″) skip not exceeding 1/4 the length.

 

 

Grade Application 205: Offset

Offset is an abrupt dressing variation in the edge surface which usually occurs near the end of a piece without reducing the width, or without changing the plane of the wide surface. The allowable offset by grade is described in the table  below.

 

Grade Allowable Offset
C Select  Very Light (not over 1/64”) in 2% of pieces
D Select  Medium (not over 1/16”) in 2% of pieces
Finish  Light (not over 1/32”) in 2% of pieces
Premium Very Light (not over 1/64” ). 2% of pieces may have Medium (not over 1/16”)
Standard Very Light (not over 1/64” ). 2% of pieces may have Heavy (not over 1/8”)
Industrial Not Limited by Grade

 

Grade Application 205: Knife Marks

Knife Marks are imprints or markings of the machine knives on the surface of dressed lumber. Slight is defined as readily visible, but evident; no unevenness to the touch.  See  table below for allowances by grade.

 

Grade Allowable Knife Marks
C Select Slight
D Select Slight
Finish Slight
Premium Slight
Standard Not Limited by Grade
Industrial Not Limited by Grade

 

 

Grade Application 205: Wavy Dressing

Marks that are more uneven dressing than knife marks. Easily visible on the surface of the board; unevenness to the touch. See limitation by grade below.

 

Grade Allowable Wavy Dressing
C Select None Allowed in Grade
D Select None Allowed in Grade
Finish None Allowed in Grade
Premium None Allowed in Grade
Standard Light (not over 1/32″)
Industrial Not Limited by Grade

 

Grade Application 205: Machine Burn

Machine Burn is a darkening of the wood due to overheating by the machine knives or rolls when pieces are stopped in the machine.  See tolerances  by grade in the table below.

 

Grade Allowable Machine Burn
C Select None Allowed in Grade
D Select One per board
Finish None
Premium One per board
Standard Not Limited by Grade
Industrial Not Limited by Grade

 

Grade Application 205: Machine Bite

Machine Bite is a depressed cut of the machine knives at the end of the piece.  See table below for the limitations by grade.

 

Grade Allowable Machine Bite
C Select Very Light (not over 1/64”)
D Select Very Light (not over 1/64”)
Finish  Very Light (not over 1/64”)
Premium Very Light (not over 1/64”)
Standard Very Light (not over 1/64”)
Industrial Not Limited In Grade

 

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