Surface Checking of White Oak as Related to Mechanical Processing

This study was instigated primarily because the author noted surface checking was the only obvious difference between rough and surfaced oak boards. A more critical study was begun to investigate the surface checking differences and their causes. The purposes of this study were to determine the effect of log sawing and lumber surfacing on the subsequent development of surface checks and to investigate probable causes of any differences found. It was divided into three phases: 1) to determine the effect of several typical surfacing methods; 2) to determine the green surfacing depth necessary to produce significant surface check reduction; and 3) to investigate the board surfaces microscopically for indicators of potential surface checks. Samples were used and three sawing treatments and one surfacing treatment were included in the tests. Surface checking was found to vary widely between boards processed by circular sawing, band sawing, and green surfacing. Circular-sawn boards checked considerably more than either band sawn or green-surfaced boards. Microscopic examination of the surface layers of boards processed by the above methods showed that sawing caused many tears in the wood elements. Drying of these same boards showed that a high percentage of the checks which developed occurred in the wood rays torn by sawing. Circular sawing did more general damage to the board face than did band sawing. Tears and subsequent checking were negligible in green-surfaced boards.

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