Draw Manga. Tom Carpenter
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Название: Draw Manga

Автор: Tom Carpenter

Издательство: Ingram

Жанр: Кулинария

Серия:

isbn: 9781607657590

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СКАЧАТЬ of case-hardening are checks (small cracks), shakes (large cracks, most often radiating out from the center across the grain), and a problem referred to as honeycombing: when the board is ripped, the inside looks just like the inside of a beehive, full of tiny honeycombs. To safeguard against case-hardening, check boards along their edges and ends, paying close attention to honey-combing, the worst kind of case-hardening. If one board in a pile is affected, chances are several more from the same batch will have the same defect.

      COMMON LUMBER DEFECTS

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      Spalling is a gray to green permanent discoloration of the wood caused by fungal growth. Be sure to keep spalled lumber dry, or the discoloration will continue and spread.

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      Knots are easy to cut out of clear sections of lumber. The lower the lumber grade, the higher will be the percentage of allowable knots.

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      Case-hardened boards should be avoided when purchasing woodworking lumber. Case-hardening results from insufficient and hasty kiln-drying at high temperatures. The board dries too rapidly on the outside but stays wet within, creating stresses that literally cause it to pull itself apart until it reaches equilibrium.

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      All construction lumber sold in the U.S. bears an industry grading stamp such as the Western Wood Products Association (WWP) stamp shown above. Nominal softwood lumber is graded similarly, but usually the stamp doesn’t show. Here’s how to decipher grade stamps:

12 Identifies the mill. This can be letters or numbers.
1&BTR This is the grade of lumber, in this case #1 Common and better, an excellent furniture grade.
WWP The grading association that graded the board, in this case the Western Wood Products Association.
S-DRY The condition of seasoning at the time of surfacing, in this case dry, or seasoned lumber below 19% moisture content. If the stamp read KD-15, it would denote kiln-dried lumber with a maximum of 15% moisture content. Product stamped S-GRN stands for unseasoned (green) lumber containing more than 19% moisture content.
DOUG FIR-L Indicates the wood species, in this case, Douglas fir.

      Slide your measuring tape across a 2 x 4 and you’ll discover that it doesn’t actually measure two inches by four inches. In fact, it will be ½-in. shy in both directions. In its rough state, when the lumber was originally ripped into studs, this same piece was in fact a true 2 x 4. But after drying, it shrank a little. Then it was surfaced (planed) on all four faces, and it shrank a little more.

      When you buy standard softwood lumber at your home center, surfaced and jointed on all faces and edges, the industry sells it to you in finished dimensions, but still describes it in nominal dimensions—the size it was before milling.

      A piece of softwood lumber with a nominal 1-in. thickness is generally referred to as a board, while nominal 2-in.-thick softwood is called framing stock (as in studs, joists and rafters), or dimension lumber. The chart below lists nominal and dimension lumber sizes for the stock you’ll find in home centers.

      Softwood lumber is graded by strength and appearance as well as moisture content. For woodworking applications, the three common grades to know are Select, Finish and Common (See the chart, below). While boards in the Common grade categories may contain some blemishes and knots, Select and Finish grades are clear or nearly clear of defects. Be aware, however, that boards within any grade may exhibit some degree of natural distortion (cupping, bowing, twisting), so it’s important to examine each board carefully by sighting along its length and width before you buy.

SOFTWOOD LUMBER GRADES
GRADE GRADING CRITERIA
B Select and BTR Highest quality lumber with little or no defects or blemishes. Nominal sizes may be limited.
C Select Some small defects or blemishes permissible, but still largely clear and of high quality.
D Select One board face usually defect-free.
Superior Finish Highest grade finish lumber with only minor defects.
Prime Finish High quality with some defects and blemishes.
No. 1 Common Highest grade of knotty lumber; usually available by special-order.
No. 2 Common Pronounced knots and larger blemishes permissible.

       Nominal vs. dimension softwood lumber sizes

NOMINAL FINISHED
1 x 2 ¾ x 1½
1 x 3 ¾ x 2½
1 x 4 ¾ x 3½
1 x 6 ¾ x 5½
1 x 8 ¾ x 7¼
1 x 10 ¾ x 9¼
1 x 12 ¾ x 11¼
DIMENSION LUMBER SIZES
2 x 2 1½ x 1½
2 x 3 1½ x 2½
2 x 4 1½ x 3½
2 x 6 СКАЧАТЬ