Sawtooth forces in cutting tropical hardwoods native to South America

      As a result of design, operation, and maintenance, sawblades used in tropical sawmills can cause many problems. Improvements in these areas are needed to reduce the waste associated with sawing of tropical species that are regarded as difficult to cut. In this study, cutting experiments that simulated bandsawing of tropical hardwoods showed the effect of chip thickness, moisture content and edge condition on the forces acting on the sawtooth. Forces were measured in three directions: parallel, normal, and lateral to the cut. Peak principal forces were 1.4 to 2.1 times as large as average forces. Doubling the chip thickness typically increased the principal force by a factors of 1.6. No significant difference existed in the forces for dry wood with a 0.010-in. (0.25-mm) chip or wet wood with a chip twice as thick. The normal force can be reduced by cutting wet wood, especially when using teeth that have some defects. The worst case is cutting dry wood with a thin chip. Large positive normal forces, tending to repel the tooth, can be an indicator of wear or damage and contribute to wear. Asymmetry in the tooth caused by mounting, grinding, or damage can result in the gereration of a lateral force. The highest lateral forces observed were generatred by a tooth with a damaged corner, while cutting dry, high density wood, giving an average lateral force equal to nearly 60% of the principal force for a good tooth. This appears to have implications for sawing accuracy.

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Sawtooth forces in cutting tropical hardwoods native to South America   ( )

As a result of design, operation, and maintenance, sawblades used in tropical sawmills can cause many problems. Improvements in these areas are needed to reduce the waste associated with sawing of tropical species that are regarded as difficult to cut. In this study, cutting experiments that simulated bandsawing of tropical hardwoods showed the effect of chip thickness, moisture content and edge condition on the forces acting on the sawtooth. Forces were measured in three directions: parallel, normal, and lateral to the cut. Peak principal forces were 1.4 to 2.1 times as large as average forces. Doubling the chip thickness typically increased the principal force by a factors of 1.6. No significant difference existed in the forces for dry wood with a 0.010-in. (0.25-mm) chip or wet wood with a chip twice as thick. The normal force can be reduced by cutting wet wood, especially when using teeth that have some defects. The worst case is cutting dry wood with a thin chip. Large positive normal forces, tending to repel the tooth, can be an indicator of wear or damage and contribute to wear. Asymmetry in the tooth caused by mounting, grinding, or damage can result in the gereration of a lateral force. The highest lateral forces observed were generatred by a tooth with a damaged corner, while cutting dry, high density wood, giving an average lateral force equal to nearly 60% of the principal force for a good tooth. This appears to have implications for sawing accuracy.

Author: Loehnertz, S. P.; Cooz, I. V.

Source: (Research paper FPL ; RP-567):16 p. : ill. ; 28 cm.

Citation: Loehnertz, S. P.; Cooz, I. V.  .  Sawtooth forces in cutting tropical hardwoods native to South America   (Research paper FPL ; RP-567):16 p. : ill. ; 28 cm..

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