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As moisture contort increases, wood expands In width but not In length.

As moisture content decreases, wood shrinks In width but not In length.

As moisture content decreases, wood shrinks In width but not In length.

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A Changes in air humidity cause

• changes in wood moisture content. When humiditv and the moisture w content of wood go up, the wood expands. When humidity and the moisture content of wood go down, the wood shrinks. Unfortunately, wood doesn't expand and shrink uniformly. Dimensional changes in the direction of the grain are so small that they can be ignored. Across the grain, however, the expansion and shrinkage will be quite noticeable.

The drawing shows how this difference in the amount of expansion or shrinkage changes the angles in a miter joint. These changes in the miter angles are responsible for the gaps in the miters on your sister-in-law's table. The evaporative cooler is probably aggravating the problem by creating a humidity range greater than the normal seasonal humidity range.

The only way to stop the wood from expanding and shrinking is to stop the moisture content from changing. Some surface coatings (finishes) will slow the change in moisture content in wood but no finish will stop it. In a nutshell, if you can't hold the humidi-

ty in the air to within a narrow range, you can't stop the miter joints from opening up.

In well-designed furniture, the pails are arranged so the wood can expand and contract without problems.

Bob Moran Assistant editor

Lowdown on Furniture Polish

QMy parents oil their furniture •once a week with furniture polish. Some of the furniture is veneered. Is this healthy for the furniture?

Avian Wilson Englewood, CO

Alt makes no difference whether • the wood is solid or veneer, nor is the species of wood important. When you oil your furniture with any polish, oil, cream or treatment from the supermarket you're putting a very thin layer of oil on top of a finish.The oil is intended to keep liquids such as oil, water and perspiration out of the wood. The idea that you need to replace the natural oils in the wood is nonsense. With few exceptions, such as teak and rosewood, the wood never had any natural oil in it; and teak and rosewood don't need their oil replaced.

Furniture polishes contain a very light oil that evaporates. The oil helps remove certain kinds of dirt and grime from the furniture and leaves a film that smears when you touch it, but also makes the furniture shine. The cut (weight) of oil used in a polish determines how quickly it will evaporate. When its gone, the shine that it gave the furniture is gone.

Clear polishes contain only oils. Polishes that appear milky are emul sions, mixtures of water and oil. Water helps soften and remove certain kinds of dirt and grime that oil won't touch.

So what good are furniture polishes? They make dust stick to your dust rag. They help in removing dirt and grime from the furniture. They make your furniture shine by leaving a thin film of oil on the surface. They create a low-friction surface that allows scuffs to skid off instead of scratch. More subjectively, they spread a pleasant scent around the room to give you the feeling that the room is clean.

Choose a polish for its cleaning characteristics, ease of use, scent, its shine and for the amount of smearing vou can tolerate.

Bob Fi.exner Finishing consultant Norman, OK

Drying Thick Slabs

QI have a 2-ft. long x 15- in. dia. •section of the stump end of a soft maple log that I want to cut into ¡-in. or 2-in. thick slabs for tabletops. How do I keep the wood from cracking as it's drying out? Should I sau* the log into slabs, or let the whole section dry first?

George Yeager Evansville, IL

A Drying slabs of wood for table-• tops is risky at best. Stump wood usually has interesting grain patterns, but those patterns dry with unusual shrinkage, which encourages warps and cracks.

Here's how vou am try to drv the w w wood. First, cut the log into slabs a little thicker than you want for the table-top to allow for warp and shrinkage. Seal the end grain and any area around knots to prevent fast drying. Asphalt roofing cement is a good sealing material, or try "Anchorseal," a wax emulsion specially formulated for sealing wood during drying (available from U.C. Coatings. P.O. Box 1066. Buffalo, NY 14215. 716-833-9366).

Dry the slabs very slowly. One way to slow down the drying is to put the slabs in a freezer or cold room for six months or longer. Another method is to put the wood outside in a cool, shady spot with high humidity and lit-

6 ▲ JANUACY/FEBR'JAfcY

Q&A

tic wind. There is always the risk of the wood getting moldy and stained.

For a stable tabletop, you'll need to get the moisture content of the wood down to 6 or 7 percent. To do this, youll have to monitor the moisture content with a moisture meter until it drops to about 20 percent. After that, put the wood in a heated drying area like a solar kiln or a heated room to drv it to the 6 to 7 percent range.

An alternate approach is to soak the wood in PEG (polyethylene glycol) (available with instructions from Constantinc's, 2050 Eastchcstcr Rd., Bronx, NY 10461.212-792-1600). PEG reduces shrinkage (and the cracking and waiping that result) by replacing the moisture in the wood.

Dr. Eugene Wengert Professor, wood technology Virginia Polytechnic Institute Blacksburg, VA

Clearing Planer Chips

QWood shavings stick to the out•

• feed roller of my 20-in. Jet planer and get pressed into the freshly planed surface of the stock. I've cleaned the roller thoroughly hut the shavings soon build up again. What can I do?

Klemens F. Johnson Camano Island. VVA

A Planer chips should never get to

• the outfeed roller because they can mar t he surface of vour stock even a*

if they don't stick to the roller. Your problem is poor evacuation of the chips.

The chips should be tunneled up and out through the dust opening by the chip breaker. If there's no dust collector attached. chip removal depends solely on the chips being thrown by the cutterhead, and some chips don't make it. They can easily wind up pressed into the wood as it passes under the outfeed roller. You can minimize the number of chips left behind by taking shallower cuts, using slower feed rates, keeping the knives sharp and properly adjusted, and by checking that there are no obstructions in the exit opening.

Some machine makes, including your Jet, require a dust collector for proper chip removal. A 20-in. planer like yours needs a collector that moves about 1200 cubic feet of air per minute.

Kelly Mehler Furniture maker Berea, KY

A Shavings from resinous wood

• can be so tacky that they require much more than normal air flow from a collector for proper removal. I gave up on one batch of pine because shavings stuck to everything and left a resinous residue on all my tools. I've also had problems in especially cold, dry weather when static build-up caused every stray shaving to cling tenaciously to the nearest surface of the machine. After a few minutes of operation. I couldn't see the planer under its plumage of wood shavings. A pan of water on the wood stove raised the humidity enough to solve the static problem.

Bob Moran Assistant editor

Restoring Planes

QI recently bought some old planes

• with wooden bodies and metal blade mechanisms. The blades need to be reground and honed, but should I clean up and polish the entire blade? What '.s the best way to overhaul these m old metal parts?

Theodore Rose Waxahachie, TX

A Your planes are usually termed

• "transitional" because they were once thought to be a transition between wooden and metal planes. In reality, Stanley and other makers w mr made this type of plane for carpenters at the same time that thev made all-metal planes that could be adjusted with more precision for more demanding woodworking.

To clean the parts, first disassemble the plane. The wooden parts are varnished. and some of the metal parts have a shiny finish called "japanning." To protect your plane's antique value, do not strip any finished surfaces with paint remover. Live with the nicks, chips and stains. You can clean the surfaces with a toothbrush and paint thinner. Remove rust with steel wool and protect the bare metal with a rust inhibitor such as WD-40.

To restore the cutting edge, first, grind the bevel to remove nicks and establish the bevel angle. (See AW, #19, page 8 for more on shaping a plane blade.)

Next, flatten the back of the blade for about 1 in. behind the cutting edge. I do this by rubbing the blade on a piece of emery cloth placed on some %-in. thick glass. I finish with a medium and a fine sharpening stone. For the edge to be razor sharp, you must polish this back surface until you can literally see vour reflection in the steel.

Finally, hone the bevel to the same degree of polish.

For more information on transitional planes and sharpening, see mv book Restoring, Tuning, and Using Classic Woodworking Tools.

Michael Dunbar Contributing editor

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