in the surrounding air, fluctuating with the
seasons. This means that the same piece of
wood can have slightly different dimensions
at different times of year or if moved from
the shop to an environment that is markedly
wetter or drier. It’s important to know how
to estimate these changes ahead of time and
plan for them when building furniture.
The best way to predict how dimensions
will change from season to season is to
measure the wood movement in a board
over the course of a year. For this purpose,
I have a few “moisture boards” hanging in
my shop. One is a wide, white-pine plank
and another is a crosscut scrap from a cherry
tabletop. I use the white pine to estimate the
movement in drawer bottoms and case backs;
its movement is similar to that of basswood
and aspen, other woods I use for those tasks.
Cherry moves much like other hardwoods.
I measure the boards’ width throughout the
year and mark the readings on the boards.
Because they mirror what the rest of the wood
in my shop is doing, as well as the moisture
content highs and lows, I use them to gauge how tightly to fit
drawers or panels in any season.
Here’s how it works: When I’m ready to fit drawers into a
case piece, for example, I consult the moisture board. If the
board measures 14 in. wide at the driest time of year and
145 ⁄ 32 in. at the wettest, and measures 14^1 ⁄ 32 in. today, I know to
expect a slight amount of shrinkage and much more expansion
during the coming year. If the drawers are 7 in. wide, or half
as wide as my moisture board, I can calculate fairly accurately
how much movement to expect (about half of what the board
says, or^1 ⁄ 16 in. expansion and^1 ⁄ 64 in. shrinkage). If I’m unsure, I
tend to err on the side of a slightly larger gap.Work with dry wood and heat your shop
I prefer to work with wood as dry as is practical, so that table-
tops or case sides will expand slightly before any shrinkage
occurs. If the parts expand first, they can work against any tight
fasteners and create some slack for later contraction.
On the other hand, on frame-and-panel work such as cabinet
doors, I don’t worry so much about a little excess moisture. I’d
rather have the panels shrink a little instead of expanding and
blowing out the joints.
To help avoid dramatic changes in climate when moving a
finished piece from my shop to its destination, I heat my shop
as I do my house. This results in a moisture content somewhere
between 7% in winter and 11% in summer. Also, a good finish
will slow moisture transfer (but won’t stop it).
There are a variety of ways to outfit a shop with heat, but if
this isn’t practical, you could always store your lumber in the
dining room—if you can get away with it. :16 F I N E W O OdW Or kI NgStep 2: keep
track of your
Shop’S climate
To predict how furniture
components will expand or
contract in the future, it is
important to know the working
conditions in the shop. Hack
uses scraps to create a
seasonal barometer of wood
movement (top). By tracking
and recording this moisture
board’s width throughout the
year, he can measure the board
on any given day and assess the
seasonal humidity of the shop.
For tasks such as fitting a draw-
er, Hack consults the moisture
board to predict how much the
drawer front will expand and/
or contract and to decide the
amount of gap to leave along
the drawer opening (bottom).boards drier inside than on the surface. If I have time, I cut
parts to rough dimension first and let them acclimate further
for a few days. I do the same when I’m milling parts to their
finished thickness. When planing, work both sides evenly and
let the parts acclimate again. Planing only one side can cause
moisture-induced warp.Gauge and plan for seasonal movement
Even after careful seasoning and milling, wood’s moisture
content will continue to balance itself with the relative humiditygetting startedcontinued
FWSIP08BF_GS.indd 16 6/8/07 4:12:01 PM