Wood movement is one of the most perplexing situations for woodworkers. Increases or decreases in moisture can warp panels, crack tabletops, delaminate glue-ups, loosen or split joints, and generally wreak havoc.
Knowing how much moisture is trapped in a board helps you during the milling process, when fitting parts, and even when making repairs. It’s essential to know when the moisture content (MC) is low enough in a pile of rough lumber to start milling it to size (below 12%, depending on the region and season). If the wood continues to move after milling, you’ll have finished parts that warp and cup. You also need to know that all the boards for one project have the same MC, which helps ensure that movement occurs at the same rate in all the parts.
You can determine the MC of lumber using a mathematical formula, but it’s not easy. You need to cut a section of the board, weigh it, dry it in an oven for a period, weigh it again, then put it in the oven and repeat until the board stops losing weight. Finally, you have to dig out a calculator and punch some numbers. The process can take a couple of days—not very convenient.
A much quicker way to monitor MC is to use a moisture meter. According to our surveys, most FWW readers don’t own one. That’s a shame, because these tools can help any home-shop woodworker avoid the damaging effects of wood movement in a project. And today’s moisture meters are more affordable than ever.
When it comes to measuring the MC of lumber, you have two options: pinless and pin-type meters. In general, pinless meters are more appropriate for home shop woodworkers. They’re accurate and easy to use (see FWW #210 for a review of pinless meters for under $200). But pin-type meters are ultimately more accurate than pinless meters for determining the exact moisture content of a specific area on a board. A pin-type meter may be suitable if you dry your own lumber or consistently work with thick wood and are willing to do a bit of destructive testing in the board to find the MC with pinpoint accuracy.
Here’s a look at a selection of pin-type meters for under $200. Among this group the Best Overall is the mini-Ligno E/D. It features a bright, easy-to-read LCD screen, programmable species correction, onboard storage for different-length pins, and an ergonomic shape that makes it comfortable to push the pins deep into hard wood.
For Best Value, I chose the Electrophysics MT90. At $66, it pretty much puts to rest any cost reason for not having a moisture meter in the shop. The meter is simple to operate, has a bright moisture level indicator light, and is compact.