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A Quiz to Test Your Knowledge of the Natures of Lumber : Woodworking: Without understanding the strengths and weaknesses of wood, it's easy to make mistakes.

May 12, 1990|A.J. HAND | A.J. Hand is a writer with the Los Angeles Times Syndicate

I've been working wood nearly all my life, but it took me more than 20 years to really understand the nature of the material--its strengths, its weaknesses, how it breathes and moves. As a result, I made mistakes. Guitars I made in the summer during college cracked when winter came. Glue joints fell apart. Miters that fit perfectly at first slowly opened up and looked several degrees off.

If things like this happen to you, maybe you don't know enough about your medium. Here's a little quiz to check your knowledge. Warning: Questions may have more than one right answer.

1. You are gluing up the three main boards that make up the pine table top shown in the sketch. Which glue will produce the strongest joints?

A. Epoxy.

B. Ordinary white glue such as Elmer's.

C. It doesn't really matter.

2. The reinforcing cleat glued with a tongue-and-groove joint across the end of the table-top shown in the sketch will:

A. Cover unattractive end grain.

B. Help prevent the table from warping.

C. Cause the ends of the table to crack.

3. You are planking a deck with pressure-treated lumber. To avoid any problems with warping and shrinkage, you should:

A. Store the lumber in the shade and nail it down as soon as possible.

B. Stack the lumber in a pile with sticks laid crosswise between each layer to allow air circulation.

C. Mist the lumber lightly with your garden hose on a daily basis until you are ready to nail it down.

4. Most of your woodworking involves soft woods, plywood and particleboard. The best blade for your power saw is:

A. A fine-toothed steel plywood blade.

B. A carbide-toothed combination blade.

C. A carbide-toothed rip blade.

5. There is no need to wear a dust mask when cutting, sanding or machining wood because it is a safe, all-natural material.

A. True.

B. False.

Answers:

1. C is the correct answer. It doesn't really matter which glue you use here because both epoxy and white glue will produce joints stronger than the wood itself.

2. A, B and C are all correct. This type of cleat is often added to table tops to hide end grain and reduce warping. Unfortunately, it also causes cracking. The reason? Wood expands and contracts a great deal across the grain, but hardly at all along its grain. When winter comes and humidity in your home drops, the table will dry out and start to shrink across the grain. But the cleat tries to fight the shrinkage. Eventually the strain becomes too great and the table-top cracks. You can prevent this by eliminating the cleat altogether, or attaching it so the table-top is free to move. One way to do this is to use screws driven through slots or oversized holes in the cleat. You can then cover over these screws with wood plugs.

3. B is the correct answer. Pressure-treated lumber normally comes fresh from treatment and packed with moisture. If you nail it down that way, it will shrink substantially and the spacing between boards can increase a quarter-inch or more. Letting the lumber dry out for a few weeks in neatly stickered stacks gives it a chance to shrink down close to the size it will attain when it reaches equilibrium.

Of course, you can install the wood wet and try to compensate for the inevitable shrinkage to come by spacing your planks closer than you want them to end up, but the result may be uneven. And if you cut any miters (maybe for a herringbone planking pattern), you'll find they open up at the heels in a few months and look very crudely cut.

4. B, a carbide combination blade is your best bet. It will make good quality cuts in all materials, and its carbide teeth will hold up to the abrasive nature of particleboard. The all-steel plywood blade will dull quickly on particleboard and won't perform well when ripping pine. The carbide rip blade will hold up well but will cause horrendous chipping and tearing in the plywood and particleboard and while crosscutting the pine.

5. B, false is the correct answer. While the dust from most domestic woods is fairly benign, many tropical hardwoods contain allergens and even toxins that may cause allergic reactions and even illness. And, of course, you should always wear a dust mask when working with pressure-treated lumber.

Scoring

There are seven possible right answers in all. Count up your correct responses and rate your knowledge of wood as follows:

All seven right: Solid as a mighty oak.

Five to six right: Strong as an oak sapling.

Three or four right: Would you believe an oak seedling?

Two or less: Nuts! You're still in the acorn stage.

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