I also see July is the most extreme difference from November, with an EMC of 15.3%. Looking at the chart, I can see the EMC of wood in Santa Barbara in November is 12.1%. Let’s say I’m building my table in November. That’s your change in moisture, the third variable in our wood movement equation.įor example, my shop’s in Santa Barbara. Then, calculate the difference between these two numbers. Next, find the month with an EMC that’s the furthest away from your current month. ![]() That number is your starting moisture content. Then find the month during which you’re building your project. If it’s not on there, look for a place close by with a similar climate. To find your board’s coefficient, find your species of wood on the Change Coefficient Chart, and use the number in the corresponding column (CR or CT)Īll you need to know for this chart is where you live and what month it is.įind your city or country.In plain sawn lumber, grain lines run horizontally along width of board in rift or quarter sawn lumber, grain lines run vertically to width of board.For plain sawn lumber, use the tangential coefficient for rift or quarter sawn lumber, use the radial coefficient.This chart is based on 30 years worth of data that the Forest Products Lab got by literally watching wood move - let's be grateful we didn’t have to do it. If the species of wood you’re using isn’t on this list, find a wood with a similar janka rating and use those coefficients. ![]() That’s because rift or quarter sawn lumber is more stable and subject to less movement over seasons. ![]() You’ll notice for each species, the coefficients in the flat sawn column are higher than in the rift/quarter sawn column. That’s the second variable in our formula for calculating wood movement. Find the species of wood you're using, determine how it’s sawn, look at the corresponding column - and done.įor example, say you’re making a tabletop out of quarter sawn walnut.įind walnut in the list of species, look at the radial coefficient column, and you’ll see 0.0019.
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