One of the things to remember when changing from one system of measurement to
SI is construction convention. The typical spacing of studs and rafters is
16-inches, center to center, which is close to 400mm. Therefore, a piece of
plywood needs to be a multiple of 16-inches in the U.S. system, or a multiple
of 400mm in SI. 1000mm is not a multiple of 400mm.
When Australia converted to SI, they "standardized" a piece of plywood as
1200mm X 2400mm. One of the reasons for doing this is so a 4-ft X 8-ft piece
of plywood manufactured before the changeover took place could be trimmed to
1200mm X 2400mm. As such, only 19mm (~3/4") in one direction would be waste
and only 38mm (~1.5") in the other direction would be waste.
BTW, two preferred length units in SI are millimetres and metres. While
there is no "centimetre cop," centimetres are a non-preferred unit. One
rationale for using mm and m as two preferred units is that the units do not
need to be shown on drawings; a dimension with no digits after the decimal
point is in millimetres, and a dimension with three digits after the decimal
point is in metres. (Note: these comments apply basically to construction.
Machining may be completely different.)
Roger Turk
Tucson, Arizona USA
Glenn McCorkle wrote:
. > On Tue, 08 May 2001 16:52:17 -0500, Sam Ewalt wrote:
. > <snip>
. > > But here's a question: In those countries that use the metric
. > > system, what is the size of a standard sheet of plywood?
. > > Perhaps there is no "standard" maybe I should say what is the most
. > > common size of a sheet of plywood? In the United States it's
. > > 4 feet x 8 feet.
. > 48*2.54=121.92
. > 96*2.54=243.84
. > Therfore, the "logical" size *should* be 120cm x 240cm
. > Or perhaps it's even "more logical" and is simply 100x200 <vbg>
. > Clarence,
. > What say you?
. > --
. > Glenn
