Wood casing IM's Furniture Design 1

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Questions and Answers

What is the result of the surface of the wood lifting in small flakes or layers?

Prevention of a smooth surface (correct)

Case hardening

A smooth surface

Diagonal grain direction

What can cause the grain of the wood to run obliquely to the longitudinal axis?

Flaking

Case hardening

Incorrect sawing (correct)

Correct sawing

What is the impact on bending strength when the grain slope is 1 in 25?

15% loss

4% loss (correct)

20% loss

10% loss

What happens when wood dries too quickly?

The surfaces dry out faster than the interior Signup and view all the answers

What is the result of case hardening on the wood?

Cuts that close ahead of the saw Signup and view all the answers

How can case hardening be cured?

By steaming and redrying Signup and view all the answers

What can be caused by incorrect seasoning of the wood?

Flaking Signup and view all the answers

Why is diagonal grain direction not important in most cases?

It does not affect the strength or appearance of the wood Signup and view all the answers

What is the primary reason for distortion, splitting, and other forms of defects in wood?

Lack of elasticity in the wood structure Signup and view all the answers

What is the purpose of weighting down during wood seasoning?

To reduce distortion Signup and view all the answers

What type of defect occurs when the plank hollows across the width and forms a rounding on the underface?

Cupping or rounding Signup and view all the answers

What is the term for the distortion that occurs when the wood remains flat but bends edgewise on its own plane?

Springing Signup and view all the answers

What is the primary cause of end splitting in wood?

Too rapid drying Signup and view all the answers

What is the term for the small splits that occur on the wood surface along the grain due to too rapid drying in hot sun?

Sun checking Signup and view all the answers

What is the term for the distortion that occurs when the plank twists on its longitudinal axis, resulting in straight long edges but curved diagonals?

Twisting Signup and view all the answers

What is the term for the synonymous terms for distortion in one or more directions?

Warping and casting Signup and view all the answers

What is the primary purpose of drying wood?

To prevent insect damage and weathering Signup and view all the answers

What is the method of drying wood that involves air circulation around every piece of lumber?

Natural drying Signup and view all the answers

What is the name of the structure used for kiln drying?

Dry kiln Signup and view all the answers

What is the term for the tendency of wood to shrink and swell?

Drying properties Signup and view all the answers

What is the unit of measurement for lumber that is 12 inches wide and 1 inch thick and 1 foot long?

Board foot Signup and view all the answers

What is the main axis of the tree in relation to the wood grain structure?

Same direction as the fibers Signup and view all the answers

What is the term for the process of scientifically heating wood to dry it?

Kiln drying Signup and view all the answers

What is the primary benefit of kiln drying over natural drying?

Faster drying time Signup and view all the answers

Study Notes

Wood Defects

Flaking: wood surface lifts in small flakes or layers, preventing a smooth surface, due to structural weakness or incorrect seasoning.
Diagonal grain: grain runs obliquely to the longitudinal axis, making surfacing more difficult, and reducing impact strength and bending strength.

Case Hardening

Occurs when wood dries too quickly, causing dry outer layers to be in tension and moist interior in compression.
Cuts that close ahead of the saw are often due to case hardening.
Can be cured by steaming and redrying.

Important Properties of Timber

Strength and related properties of toughness, rigidity, and hardness.
Workability.
Drying properties and related tendency to shrink and swell.
Bending qualities.
Grain structure and figure pattern.
Gluing properties.
Finishing.
Resistance to weathering and insect damage.

Methods of Drying Wood

Natural drying (air-drying or sundrying): lumber is strip-piled at a slope on a solid foundation.
Kiln drying: done in a dry kiln using steam pipes.
Water seasoning.

Unit of Measurement

Board foot: a piece of lumber 12 inches wide and 1 inch thick and 1 foot long.

Types of Wood Grain Structure

Straight grain: fibers running in the same direction as the main axis of the tree.
Inter-locked grain: grains in successive layers and in opposite directions.

Artificial Defects

Caused by incorrect seasoning, creating internal strains and stresses.
Normally, the natural elasticity of a healthy wood structure distributes these stresses evenly.
Weighting down during seasoning helps to reduce distortion.

Types of Distortion

Cupping or rounding: the plank hollows across the width, forming a rounding on the underface, often due to incorrect piling.
Bowing: the plank is curved like a bow throughout its length.
Springing: the wood remains flat but bends edgewise on its own plane.
Twisting: the plank twists on its longitudinal axis with the result that the long edges are straight, but the diagonals are curved.
Warping, casting: synonymous terms for distortion in one or more directions.
End splitting: the butt end of the plank splits open, usually caused by too rapid drying.
Sun checking: small splits along the grain caused by too rapid drying in hot sun.

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