RE: [CAD_CAM_EDM_DRO] Re: Conversion

Hi,

Sounds like they used 1/25.4*1000 to convert meters to inches
(which gives 39.3700787402 on my HP48SX), but when you take that
and punch the digits back into your own calc, the rounding errors
might give you something other than 25.4. Currently, the
international standard is 1"=25.4mm exactly, no matter what
somebody's conversion program may tell you. This hasn't always
been true. Moore's "Foundations of Mechanical Accuracy" has an
interesting history of this standard (pg 104). For example,
(paraphrasing, credit to Moore): the Mendenhall Order of April 5,
1893, of the USGS, stated that the value of the inch would be
derived from 1 inch = 25.4000508mm. In 1922 the relationship of
the British yard to the meter was set so that 1 inch = 25.399956.
In 1959 Canadians re-defined their inch so that 1 inch = 25.4mm
EXACTLY. In 1959, English-speaking nations compromised on the
Canadian inch. The length of the meter that the inch is based on
is another story, also described in the book. Great book, by the
way, even just for the pictures.

HTH,

Carlos Guillermo
VERVE Engineering & Design

-----Original Message-----
From: mariss92705 [mailto:mariss92705@...]
Sent: Friday, June 21, 2002 1:39 PM
To: CAD_CAM_EDM_DRO@yahoogroups.com
Subject: [CAD_CAM_EDM_DRO] Re: Conversion

Hi,

Loaded Google with "inch mm convert", looked thru the first dozen
or
so returns until I found
http://galaxies.com/Info/Math/Conversion.htm

I got 39.3700787401575" per meter, took the 1/x of that using
Windows
calculator because of its nearly unlimited digit resolution.

Took all of 5 minutes.

Mariss

--- In CAD_CAM_EDM_DRO@y..., Dave Lantz <dlantz@a...> wrote:
> where did you look it up? sounds like a good resource!---Dave
L.
>
> -----Original Message-----
> From: mariss92705 [mailto:mariss92705@y...]
> Sent: Friday, June 21, 2002 1:26 PM
> To: CAD_CAM_EDM_DRO@y...
> Subject: [CAD_CAM_EDM_DRO] Re: Conversion
>
>
> Hi,
>
> I looked it up and I got 25.399999999999987300000000000006 mm
equals
> 1". Seems 2.54 is accurate to 16 places.
>
> Mariss
>
> --- In CAD_CAM_EDM_DRO@y..., "James Owens" <wotisname@l...>
wrote:
> > Hi,
> >
> > I'm working on a DRO and am having some confusion over the
> conversion of
> > metric units to inches and back again. The device should be
able
to
> read
> > glass scales down to 0.001mm or 1 micron so it is important to
get
> this
> > right.
> >
> > I have always used 1" = 25.4 mm but on trying to work it out
with
a
> little
> > more accuracy I find that an English mile = 1.609 kilometres
or
1" =
> > 25.39457071 mm. but this figure changes depending on who it is
> coming from.
> >
> > Does the list have any opinions on this.
> >
> > Regards,
> >
> > Terry
>
>
> Addresses:
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Addresses:
FAQ: http://www.ktmarketing.com/faq.html
FILES: http://groups.yahoo.com/group/CAD_CAM_EDM_DRO/files/

OFF Topic POSTS: General Machining
If you wish to post on unlimited OT subjects goto:
aol://5863:126/rec.crafts.metalworking or go thru Google.com to
reach it if you have trouble.
http://www.metalworking.com/news_servers.html

http://groups.yahoo.com/group/jobshophomeshop I consider this as
a sister site to the CCED group, as many of the same members are
there, for OT subjects, that are not allowed on the CCED list.



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