Relating Specific Gravity and Mechanical Properties of Hardwoods to Machining Defects

Selecting another wood species is often based upon the initial cost of the raw material. However, the cost to manufacture a satisfactory surface can add substantially to the final cost of the product. Available data for percentage of machining defect-free pieces of 25 hardwoods were combined with specific gravity and selected strength properties to develop models which estimate the percentage of machining defect-free pieces. The defects included torn grain, raised grain, fuzzy grain, and chip marks. The models were developed by stepwise regression and contained up to 12 independent terms of combinations of strength properties. The models accounted for up to 70 and 89 percent of the variability for knife planing and shaping, respectively, percentage of defect-free pieces. The percentage of machining defect-free pieces of other hardwoods could be estimated by substituting their specific gravity and strength properties into the models. The percentage of machining defect-free estimates could help select a substitute species of comparable machinability.

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