can you explain the us metric unit?

Discussion in 'Education' started by yaasaay, Jun 5, 2011.

  1. yaasaay
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    yaasaay Junior Member

    hi guys

    can you explain the us metric unit?


    I don't understand this unit

    here examples if you can explain it and change it to cm Centimeter or mm Millimeter

    and please identify which is the length and width and the thick

    to be more clear

    4-1/4 x 4-1/4 x 5-1/4" cedar (leg)

    1 x 4-1/2 x 13-1/2" cedar (arm post)

    1 x 2-3/8 x 11" cedar (bracket)

    thanks
     
  2. thedutchtouch
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    thedutchtouch Junior Member

    the US uses a measurement system of feet and inches, it is NOT the same as europe/the rest of the world's metric system. when written a single ' means feet and a double " means inches, for example i'm 6'2" tall, or 6 feet, 2 inches the conversion from inches to cm can be done online, here: http://tinyurl.com/3o773ao
     
  3. troy2000
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    troy2000 Senior Member

    Those measurements are apparently all in inches, judging by the way they include fractions. Grab your calculator, or google 'metric conversion'; an inch equals 2.54 cm.

    Now here's where it can get confusing. If a piece of wood is described with a couple of small whole numbers that aren't identified, then with one that is, someone is probably describing a standard piece of store-bought lumber cut to a particular length. For example, '2x4 x 94 1/4"' and '2x4 x 7' 8 1/4"' are two ways of describing a board that's a nominal two inches thick and four inches wide. And a nominal 2x4 is really 1 1/2" thick and 3 1/2" wide....
     
  4. yaasaay
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    yaasaay Junior Member

    thanks

    what about this 5-1/4"

    what does (5 dash) mean?

    is it same to 6'
     
  5. Olav
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    Olav naval architect

    5-1/4" means "five and a quarter inch". So:

    5" = 5 * 25.4 mm = 127 mm
    1/4" = 0.25" = 0.25 * 25.4 mm = 6.35 mm

    TOTAL: 127 mm + 6.35 mm = 133.35 mm
     
  6. troy2000
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    troy2000 Senior Member

    As Olav pointed out, a dash usually just connects a fraction to a whole number, to make it clear that they're part of the same measurement. Some people use them; some don't.

    Interesting. You're asking questions about things I've taken for granted my entire life. I know our measurement system confuses people who are aren't used to it. But until now, it hadn't really occurred to me that even the way it's notated has to be learned, rather than just automatically making sense.

    It's like using a hammer. I grew up with a father who was a carpenter, and I honestly don't remember learning to drive nails; it came to me as naturally as walking did. So as a contractor I was shocked when I hired young men with no experience, and realized that people aren't born knowing how to properly hold and swing a hammer...
     
  7. yaasaay
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    yaasaay Junior Member

    Thank you all
    I have really benefited from your responses

    and Mr, troy2000

    as you said, many people confuse when he use this unit not because it is complicated
    but because we accustomed with our measurement

    like me *_^
     
  8. Aharon
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    Aharon Junior Member

    Troy, here's another funny thing about our minds: if you were raised and schooled in a country and then move to another, with a different language, you will revert to your mother's tongue every time you make calculations in your mind, count money, etc. Perhaps because when we make aritmetic operations, our brains "see" the words associated to the numbers not as "names" (nouns), but as quantities.
    Now, if every normal human being has 10 fingers, isn't it a bit arrogant to stick to a measuring system based on some old guy's thumb size? Don't get mad at me, I'm just asking... :)
    way to go, yaasaay! Share your project with us!
     
    Last edited: Jun 5, 2011
  9. troy2000
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    troy2000 Senior Member

    You have to remember that unlike the metric system, ours wasn't established deliberately, arbitrarily and logically, then presented to the world. It's just a handful of conveniently-sized weights and measures that slowly became standardized and accepted over time.

    And we haven't kept them because of arrogance, but because of habit -- and later, from a reluctance to pay the costs of conversion in one fell swoop.

    'Arrogant' might better describe those people who created a completely new system out of whole cloth, and set out to convince the entire world to use it...;)

    Although I'll admit their arrogance seems to have been justified, because they eventually succeeded. Even the US is a dual-system country, and slowly but surely the metric system is superseding our customary one.
     
  10. Sand crab
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    Sand crab Junior Member

    calculator

    Yaasaay, If you are using a computer with windows 7 then it probably comes with a calculator that converts any unit of measurement to any other including angstroms, hectares, etc. It will do feet and inches to metric or the other way around. We aren't totally arrogant. We do use those systems that make sense. I beleive our numbers are based on arabic systems. Roman numerals were getting really to be a pain. :p
     
  11. hoytedow
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    hoytedow Fly on the Wall - Miss ddt yet?

    Most 2x4's sold are not 94 and a quarter", but more like a rough 96", unless the store caters to Hobbits. :p

    That is why they are calle 2(")x4(")x8(').
     
  12. hoytedow
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    hoytedow Fly on the Wall - Miss ddt yet?

    So-called Arabic numeral system actually originated in Hindu India. The Arabs brought it to the western world. Thanks.
     
  13. yaasaay
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    yaasaay Junior Member

    In fact I don't know why we take or use a Indian numeral system rather arabic numbers

    I have started to use arabic numbers when I was in high school when I knew the number 0123456789 are arabic numbers


    but this is what I don't know

    why when I was in elementary and middle school they have teached us a other system not our system

    I am not arrogant however I see the 0123456789 is more Efficient than other numbers
     
  14. hoytedow
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    hoytedow Fly on the Wall - Miss ddt yet?

    Wow! I didn't know you used another system. What is it?
     

  15. troy2000
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    troy2000 Senior Member

    You forgot to allow for the bottom and top plates, Hoyt.:)

    Actually, standard 2x4 wall studs in California are exactly 92-1/4" (7' 8-1/4"). Why? Simple: when you use them to build a wall, nailing them between a single 2x4 floor plate and double 2x4 top plates, you wind up with a wall that's 3/4" taller than eight feet, (keeping in mind that each nominal 2x4 plate is actually 1-1/2" thick). After you sheath the ceiling with 1/2" drywall, you're left with a space to drywall that's 1/4" more than eight feet.

    Strangely enough, standard drywall sheets are exactly 4 feet wide and eight feet long. So why do you want that extra 1/4", regardless of whether you lay your drywall vertically or horizontally? Two reasons. The first is that it gives you a little fudge factor. You don't have to stuff the drywall into a tight spot or trim it, if the ceiling or floor is a little wavy or if something isn't quite square, or if the ceiling drywall isn't quite tight near the wall.

    The second reason is that once nailed in place with its upper edge pressed tight against the ceiling, drywall doesn't normally touch the floor. So it's less likely to get damaged from wicking up water or other liquids, if the floor gets wet for any reason. Of course, the gap is hidden behind baseboards.

    Obviously lumber stores also sell boards that are 2x4 x 8'-0". But around here, people don't normally use them for studs in standard house construction.

    All the above also applies if you decide you want thicker walls, and some places sell 2x6 x 92-1/4" studs.
     
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