Selecting Lumber

ROUGH OR SURFACED?

Which should you choose? Ready-surfaced lumber saves you the time it takes to plane and joint. But if the wood should cup or bow, you’ll have to live with the imperfections. Rough-sawn lumber gives you some extra stock so you can true a slightly warped board, making the surfaces perfectly straight and flat.

Many craftsmen insist that you can get truly flat lumber only by surfacing it yourself. But this can be impractical, especially if you have a small shop and limited surfacing capabilities. Unless you have a wide jointer and a large planer, it makes sense to buy surfaced lumber (S2S – surfaced two sides) for noncritical parts that don’t have to be perfectly true. When making critical parts such as door frame members and drawer sides, however, you should always start with rough lumber and true it.

S4S – surfaced four sides – stock should be your last choice. It just isn’t worth the money you pay for jointing the edges. Provided you have a jointer, you can make much straighter edges if you joint the parts as you cut them to size.

SHOP-DRYING

After purchasing the stock, let it rest in your shop for a week or two (per inch of thickness) before working with it. The same holds for stock you’ve stored in a building separate from your shop. Resist the temptation to get to work immediately — you might have to do a lot of work over again!

LET THE WOOD REACH EQUILIBRIUM

Wood typically expands or contracts whenever you change its location, due to differences in relative humidity. When you first bring a board into your shop, it will be in motion. If you attempt to work it too soon, problems will result. The surfaces that you plane perfectly true today may be less than flat by tomorrow. Joints that fit beautifully on Monday may be nothing to crow about by Friday.

To avoid these problems, let the wood stabilize in its new environment. Stack it in a corner or on a rack until the moisture content of the wood reaches equilibrium with the relative humidity in your shop. This is called shop-drying, and it usually takes just a few days. Most craftsmen wait a week or more to be safe.

Once the lumber has stabilized, joint and plane the surfaces straight, flat, and square to one another. Although jointing and planing are both surfacing operations, they are actually very different.

• Jointing trues a surface and shaves it flat. It also cuts one surface at a precise angle (usually 90 degrees) to another.
• Planing cuts one surface parallel to another and reduces the stock to a precise thickness.