Woodworker's Journal 2004-28-6, страница 7

QUESTIONS

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SWhal is the ideal humidity level for a workshop?

Darin M. Peck Greenville, Maine

A

"Humidity" is more accuratcly called "relative humidity" (RH), which is the actual amount of water vapor present in the air expressed as a percentage of the maximum possible for a specific temperature. Assuming the impossible condition that climate control in a workshop is even possible, air temperature of 65° and RH of 40 percent would produce a desirable wood moisture content of about 8 percent. However, before concluding that a RH of 40 percent is "ideal," you must realize that in the real world workshop temperatures can range from 50° to 100° and the RH from 10 percent to 80 percent, changing the moisture content of wood accordingly. There's also another variable beyond the woodworker's control: furniture built in a low RH shop may end up in a high RH living room.

My explanation has been simplified by space constraints, but it's enough to let me say that "humidity" is one part of a mix of variables that we don't normally try to control in workshops. We live with what we get. The real kicker is that the construction techniques that we have developed to cope with variations in temperature and RH and consequent wood movement render the effort to achieve "ideal humidity" unnecessary.

— Ian Kirby

a I read a lot on woodworking and love the hobby very much, but there is one thing I'm not clear about regarding the horsepower information that comes with every power tool. I thought cabinet table saws with 3 HP or more required 220V, but I see there arc tabletop or contractor's saws out there that claim to have 4.4 HP.

Or, on vacuums: dust collection systems of more than 1.5 HP have to work on 220V, but you can find portable vacuums up to 6 HP that run on 110V.

Please clear this subject up for me.

Yaniv Matza Tamarac, Florida

\ Motors may be rated at two different points; one is at continuous duty horsepower, another is maximum developed horsepower. Continuous duty horsepower is defined as the maximum horsepower a motor can produce continuously (over two hours) without exceeding the temperature limitations of its components and materials. Induction motors

used primarily in bench and stationary power tools like drill presses, belt/disc sandcrs, bench grinders, and table saws are typically rated by continuous duty horsepower. These motors have a fixed speed based on their design. Typically, motors run without load at about 3,450 rpm or 1,750 rpm.

There is a wound field, called the stator, and a solid rotating member called the rotor. The rotor is not wound with copper wire but cast with aluminum. Induction motors are available in higher horsepowers than universal motors. Induction motors may be direct drive or connected to drive trains that increase or decrease the speed.

— Mike Weiby _

_s

It's ail relative: According to Ian Kirby, controlling humidity in your shop Is only one part of the picture ... e.g., where's the piece going next?

WINNER! For simply sending in his question m horsepower and voltage, Yaniv Matza of Tamarac, Florida wins

DS14DMR 14.4-volt Each

issue ive toss new questions into a hat and draw a winner.

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December 2004 Woodworker's Journal