Wood-120-2018W-Lec-3-Grading-RF.pdf

Torn grain loosened grain raised grain wavy dressing

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Torn grain Loosened grain Raised grain Wavy dressing Improper trimming Machine burn Machine bite Machine gouge Machine offset Chip marks Knife marks
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Example - Skip mark and Dog Holes “Skips” are areas on a piece that failed to surface clean Hit and Miss Series of skips not over 1/16 " deep with surfaced areas in between (may be 4, in length) “Dog Holes” are holes occurring often a result of handling logs or cants Figure 6/7: Examples of Skip and Dog – Picture captured by R. Fuerst
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Example - Torn grain Torn grain – Small pieces of wood fiber torn out below the line of surfacing. Usually occurs around natural defects such as knots, diagonal grain, irregular growth pattern Caused by too fast feed speeds, knife angle too large, and dull knifes Figure 8: Examples of Torn Grain – Picture captured by R. Fuerst
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Example - Knife Marks – (Cutter Marks) Imprints or markings of the machine knives on the surface of dressed lumber They are usually smooth to touch, but visible from certain angles. Be caused by improper jointing or setting of planer knives (warped knifes, out of balance) Excessive feed speed, Figure 9: Examples of Moulder Head – Picture captured by R. Fuerst
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3) Seasoning related defects Caused by drying and include: Checks Splits Warp (crook, cup, bow and twist) Damp stock Cell collapse Case hardening Honeycombing
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Example - Twist/Crook/Bow Twist Warping in lumber where the ends twist in opposite direction. Crook Warping along the edge from one end to the other. Cup is a deviation between edge to edge Figure 10/11/12: Examples of Twist, Crook, and Cup – Picture captured by R. Fuerst
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Example - Checks Checking is cracking that occurs mainly at the ends of the board, and run along the grain. In some cases, it can occur in the middle. Checking occurs during the drying process of lumber, usually when the lumber is dried too fast. Figure 13/14: Example of checks– Picture captured by R. Fuerst
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Hardwood Lumber Grading Wood 120 Introduction to NHGA Rules – National Lumber Grades Authority Presented by: Robert Fuerst
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NHLA – Hardwood Grading Rules The grade of a board is based on its poorer face and is determined by the percentage of this piece that can be made into cuttings of a certain quality and dimension (width and length) The higher the yield and the larger the size of clear wood the higher the grade Figure 15: Example Grading – Picture captured by R. Fuerst
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  • Fall '14
  • SimonEllis
  • Robert Fuerst,  NLGA

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