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Re: WOOD: Visually Graded Lumber - "Ripping"

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IIRC allowable knot size is also related to the board size. Dennis has previously suggested that simply designing one grade higher makes ripping acceptable, but I don't think that's correct (unless your specifying clear lumber).
Comments?
C. Utzman, P.E.

Roger Turk wrote:

Bill,

Basically, if you rip a piece lengthwise, you are repositioning the knots with respect to the edges on the piece. Knots which may have been center knots could now be edge or spike knots; loose knots permitted in the center could now be prohibited loose knots at the edges. ASTM D245 describes where in the piece knot provisions change.

PS20-2002(? My copy of PS20 is in the office and I'm not) basically says very little about detailed grading of lumber, but specifies the agencies responsible for writing the grading rules for various species. For example, WCLIB writes the grading rules only for Douglas Fir (Coast Region), WWPA writes grading rules for other western species, SPIB writes the grading rules for Southern Pine, etc.

I doubt if AWS has anything to do with it (AWC maybe, but not AWS <G>).

HTH

A. Roger Turk, P.E.(Structural)
Tucson, Arizona

Bill Polhemus wrote:

. > Someone mentioned here awhile back that if you take a dimension lumber
. > "board" such as a 2x8 and rip it lengthwise, the piece is no longer . > "graded" per the visual (or I presume, machine) grading standards, since
. > imperfections in the wood that go into the grading of it are not uniform
. > across the section. You could have one piece with a bunch of knots in it,
. > for example, while the other is relatively free of them.

. > I am trying to find "chapter and verse" where this occurs in the . > literature. I assume it is a "PS" standard or similar put out by AWS.

. > Can anyone help me?

. > William L. Polhemus, Jr. P.E.

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