Good Connections Magazine

UNDERSTANDING LUMBER VARIATIONS This arŸcle will document the effects of lumber variaŸon on the finished length of webs and cords. Here are some important definiŸons: · is lumber from nominal 2- Dimensional lumber inch to, but not including, nominal 5-inch thickness, and of nominal 2-inch or greater width. · is wood lumber that is cut to a Dressed lumber pre-defined size. It is sawn, planed, and sanded to prepare it for use. Dressed lumber has a very consistent size, although it will vary slightly due to moisture content. · exists in name only, for Nominal lumber example 2 x4. · Wood is considered if it has less than 19% dry moisture content and is considered if it has wet greater than 19% moisture content. Variance in moisture will lead to a dimensional tolerance. In this arŸcle, examples are based on a nominal 2x4 board. According to the NaŸonal InsŸtute of Standards and Technology (NIST), American SoLwood Lumber Standard (PS 20-10), the dressed size of this board is a minimum of 1 ½" X 3 ½" in dry condiŸons. Dressed sizes equal or exceed this minimum at the Ÿme of manufacture but will change over Ÿme due to variances in the moisture content. The NIST allows for an eased edge, or slightly rounded surfacing on pieces of lumber to remove sharp corners, on boards that are a nominal 4 inches thick or less. This arŸcle examines the changes to a manufactured web or chord when the dressed size varied by 1/16 of th an inch. Eased edges will also make a difference on the final cut piece and those changes are explained. This arŸcle does not consider the effects of wet/icy, warped lumber or machinery that needs repair. There are many Ÿmes when mulŸple effects are combined creaŸng a larger deviaŸon. When cu« ng with a linear saw any variaŸons in dimensions and shape will affect the sizes of the final cut piece. A small variaŸon in lumber can yield a large difference in a cut piece. While the maŸng surfaces will be in the correct locaŸons, the parts will vary dimensionally. We have prepared some specific examples to illustrate this phenomenon. All examples below are based on the programming of the Alpine ALS 4.0 Linear Saw. Alpine's ALS 4.0 Linear Saw orients the lumber to the back, against the fence and down on the L1/L2 belts. It bases all its mathemaŸcal cut calculaŸons on the data from the TRS files it receives. Lumber Width: When cu« ng an angled part and the long point is up against the fence, the width will have no effect on the overall length or the top length of the piece. (Table 1) Lumber width will affect the bo© om length of a part with the short side against the fence. In the example, the bo© om length varies by ±3/16" when the width varies only ±1/16". Wood characterisŸcs and good cu« ng: by Daniel Carlsen, Colleen Frederick and Jeff Gee Colleen Frederick, Designer DraLer Based in Grand Prairie, Texas, she creates equipment drawings and bills of materials. 4 GOOD CONNECTIONS | Summer 2019 Example 1 Table 1 Daniel Carlsen, Engineering Manager, Equipment Based in Grand Prairie, Texas, he oversees R&D & sustaining engineering.

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