Procedure for Exercise B

  1. Wood identification. FA'aminc the blocks of wood provided in the laboratory. Use the flowcharts in figures 15.S and 15.6 to identify' the type of wood. The first distinction you need to make is whether the wood has pores, or vessels. Coniferous woods do not have vessel elements and thus do not have vessels (pores). Thcv can be identified with the flowchart in figure 15.5. Woods from flowering, dicot trees do have vessels. As mentioned earlier, when the vessels are arranged in a concentric band, usually more in the carlywood, the wood is classified as ring porous. When the vessels are evenly distributed, the wood is classified as diffuse porous. The dicot woods can be identified with the flowchart in figure 15.6.
  2. The attractive figure. The figure of wood is defined as any feature or pattern in wood that enhances its bcautv. It includes the ornamental markings on the surface of timber produced by the relative arrangement of die different elements of the timber or by inherent coloring. Sometimes figure is used synonymously with the term "grain," but grain is actually the orientation of the trachcids and vessels. Grain, however, contributes to the overall figure of wood.

Examine different cuts of wood or blocks of wood showing the three planes of cut as in fig. 15.7. When the wood is sawed w ith a radial cut, the plane of the cut is along the radius of the log. The growth rings appear as more or less continuous vertical lines and fairly evenly spaced if the tree had regular growth. In reality, only a few boards can be cut along the radius. To get the most boards from a log, the mill cuts the log tangcntially so that the plane is at right angles to the radius of the log. The cutting plane intersects the growth rings in such a way that thcv look like parabolas or portions of parabolas.

When wood is sawed with a transverse cut, the plane is perpendicular to the long axis of the log. Growth rings appear as concentric circlcs. Rays appear as lines radiating from the center. Typically, this type of cut promotes more splitting and w arping of the board, so mills do not saw the broad surfaces of boards transversely.

Radial Cross Tangential Wood Cut
a. Radial cut
Wood Splitting Exercise

b. Tangential cut ^ c. Transverse cut

FIGURE 15.7 THE DIRECTION IN WHICH THE LOGS ARE SAWN DETERMINES THE PATTERNS ON THE FINISHED WOOD. (A) THE RADIAL CUT, ALSO KNOWN AS QUARTER-SAWN, PRODUCES PARALLEL LINES ON THE BOARD. (B) THE TANGENTIAL CUT. CALLED PLAIN-SAWN. PRODUCES WAVY BANDS. THE TRANSVERSE CUT (C) IS THE END OF EACH BOARD.

Was this article helpful?

0 0
Building Your Own Greenhouse

Building Your Own Greenhouse

You Might Just End Up Spending More Time In Planning Your Greenhouse Than Your Home Don’t Blame Us If Your Wife Gets Mad. Don't Be A Conventional Greenhouse Dreamer! Come Out Of The Mould, Build Your Own And Let Your Greenhouse Give A Better Yield Than Any Other In Town! Discover How You Can Start Your Own Greenhouse With Healthier Plants… Anytime Of The Year!

Get My Free Ebook


Post a comment