If I want to divide a piece of material into three equal strips, I measure
at an angle, rather than perpendicular to the side. I adjust the angle so
that the apparent width is an integral multiple of 3, and mark the
one-third and two-third points accordingly.
That way, it doesn't matter what units are on the tape or the ruler.
I'd always assumed that most people were aware of that simple approach.
Apparently not, though.
Obviously, the same approach works for any number of strips.
Bill Potts, CMS
San Jose, CA
http://metric1.org [SI Navigator]
> -----Original Message-----
> From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On
> Behalf Of Karl G. Ruling
> Sent: 2000, October 26 13:01
> To: U.S. Metric Association
> Subject: [USMA:8792] Re: building in metric
>
>
> I've been building things around my house using SI, and it's not that
> tough. Yes, it would be better if all the lumber were in rational metric
> sizes, but it doesn't really matter much. No piece of lumber is exactly
> what it's supposed to be, so I've never been able to assume that
> a piece of
> nominal 1x3 would actually be 2 1/2" wide. I've always had to
> measure it.
> If I measure it as 2 7/16" or 62mm, it's the same width, except
> that "62mm"
> is easier for me to scribble on my construction notes.
>
> As for the difficulties of dividing a 4' x 8' panel into three for the
> placement of studs (nominal 16" centers) using SI, this is also
> largely an
> illusory problem. A nominally 4' panel -- if it is truly 4' wide
> -- would
> be 1219.2mm wide. The 0.2mm is completely inconsequential; if I
> drag the
> panel across the garage floor I'm likely to rub off that much on the
> concrete, so it's not worth worrying about. So that leaves the
> panel width
> as 1219mm, which looks like a pretty ugly number to divide by 3,
> but it's
> not. Dividing it by 3 gives 46mm with a remainder of 1mm. I can
> ignore the
> remainder because it's only about the thickness of a US dime.
> There's not
> much house construction that is built to the precision of the
> thickness of
> a dime! I'm very lucky if I can achieve millimeter-precision in
> my woodworking.
>
> I find that a lot of the problems of working with building
> products made to
> hard-inch dimensions while using SI vanish when I keep in mind
> the level of
> precision required or possible. A millimeter here or there
> simply doesn't
> matter in most cases.
>
> I do appreciate it that having inch-sized building products does make
> building in SI a mental challenge (you have to get over worrying about a
> millimeter here and there), but I'm puzzled that this was an
> insurmountable
> problem for the Michigan road construction industry. What's the level of
> precision used in pouring concrete slabs or laying asphalt? What's the
> level of precision involved in bending reinforcing bar, binding
> it together
> with rebar tie-wire, and imbedding it inconcrete? Who's using telescopic
> rifle sights to lob water balloons?
>
>
