problem with drawing units

Discussion in 'AutoCAD' started by MJ, Nov 29, 2004.

  1. MJ

    MJ Guest

    Hi everyone,
    I'm using Autocad with my drawing units set to architectural and in
    inches.
    When I changed the units settings from architecture to millimetres on the
    same drawing they don't match and I suppose theres a scale difference.
    Is there a way I can do my drawings in mm and feets/inches together without
    constantly calculating the scale differences? Thanks in advance.

    Mike J
     
    MJ, Nov 29, 2004
    #1
  2. AutoCAD isn't smart enough to know the difference between units. It uses
    it's own abstract units and dresses them up according to your specification.
    If you want to convert a drawing drawn in inches to one drawn in metric, you
    will have to scale the entire drawing accordingly.

    I come up against this problem myself quite a bit since the legislation here
    is metric, but wood products are in inches, so I have a little lisp routine
    on my site which will convert units for you "on the fly". IOW you type
    inches and acad gets the metric equivalent, or vise versa.
     
    Michael Bulatovich, Nov 29, 2004
    #2
  3. MJ

    Pete Guest

    You could try this: Create a new drawing from scratch and select mm as
    units or you can choose from a number of dwt template files that are in
    metric format. Save it as a metric master drawing. Now open your drawing
    file that is in inch format. Use WBLOCK, select objects or entire drawing,
    base point 0,0,0, and check "retain". Acad will not let you use the same
    name as the dwg so you can accept the default, new block.dwg. Close the
    drawing and in the metric dwg, insert the new block.dwg (check explode) and
    insert it at 0,0,0. Now you'll have to do what Michael mentioned; scale the
    entire drawing so that one unit equals one mm. Scale factor 25.4. You'll
    have to do a dimupdate to apply the ISO-25 dimstyle to your existing dims.
    You'll most likely have some issues with this; with dimstyles and blocks
    that you used in the original dwg and you'll now have two drawings that are
    essentially the same. But it's worth experimenting with.

    Pete
     
    Pete, Nov 29, 2004
    #3
  4. MJ

    B. W. Salt. Guest

    I use a metric dimstyle and create an architectural style from that and
    scale the units by 0.03837.

    For example, if you draw a line and dimension it as metric, then create an
    architectural dimstyle from the metric one and set the units scale as
    above, then dimension the line again - you will get the feet/inches
    dimension.

    Just switch between styles as you wish.

    Or, set up the alternative units in your dimstyle as architectural
    (with the scale factor as above) and then have both in the same dimension.
     
    B. W. Salt., Nov 29, 2004
    #4
  5. MJ

    uNkulunkulu Guest

    : Hi everyone,
    : I'm using Autocad with my drawing units set to architectural and in
    : inches.
    : When I changed the units settings from architecture to millimetres on the
    : same drawing they don't match and I suppose theres a scale difference.
    : Is there a way I can do my drawings in mm and feets/inches together without
    : constantly calculating the scale differences? Thanks in advance.
    :
    : Mike J
    :
    :


    You could of course just use alternate units in the dimensions style and
    AutoCAD will give you both units just draw in metric and use alternate units
    scaled to 25.4 and you well get the imperial equivalent.


    --
    VOTE FOR AN INDEPENDENT ENGLAND
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    uNkulunkulu
    uMvelinqangi
    Mina bona wena
    mina bona lo mombi yena lo shatini
    Skat lo Boss yena fika, nika yena iwhisky

     
    uNkulunkulu, Nov 29, 2004
    #5
  6. 3>>>>>>>>>>8<<<<<<<<<37?????!!!!!

    BTW, the question was about drawing not dimensioning, per se.
    The OP wants to input metric AND imperial dimensions when drawing.
     
    Michael Bulatovich, Nov 30, 2004
    #6
  7. MJ

    B. W. Salt. Guest

    I thought you had answered that in saying that Acad knows no difference -
    which it doesn't.

    The drawing 'units' can only be defined within the dimensioning, surely,
    when everything is drawn 1:1? Then the dimensions show the correct values
    and the conversion factor depends on whether you draw (dimension) in
    metric or imperial as your major dimension. I thought that is what the
    question referred to.
     
    B. W. Salt., Nov 30, 2004
    #7
  8. MJ

    Pete Guest

    If he drew in metric units, alternate units would need to be 1/25.4
     
    Pete, Nov 30, 2004
    #8
  9. The question was a bit sloppy, so it's easy to
    misinterpret. I could be wrong. The best I could come up with for
    these situations was a transparent unit converting
    LISP as mentioned. You aren't using 3837 for conversions
    though, are you? It's 3937.

    I thought you Brits gave up inches, along with the Empire, long ago.
    When do you use them at all? In North America, we have the US
    market for Canadian wood, and our Imperial traditions, forcing us
    to use inches while our laws are written in Metric. Steel and
    concrete are generally done in metric. What a mess.

    We convert all the time, (all carry calculators for this)
    and have stacks of conversions committed to memory. The Codes
    are sloppy about "hard" and "soft" conversions (accurate and
    not-so-accurate),
    so sometimes you end up with 24" converted to 600mm, and sometimes to 610mm.

    When you get a snot-nosed idiot for a plans examiner or site inspector,
    it can get pretty funny unless you are trying to make a living at this....
     
    Michael Bulatovich, Nov 30, 2004
    #9
  10. MJ

    B. W. Salt. Guest

    Yes. Finger trouble :) I think the spacing on keyboards should be
    increased...
    Yes again, but I have been redrawing some World War II airfield drawings,
    and they are in Imperial. Not for present-day use, just to produce a
    decent copy of the original (reproduced from microfiche).

    When we 'went metric' <laugh>, all our wood and steel stayed Imperial for
    many a long year; in fact, the metric dimensions of some are just straight
    conversions of the Imperial, even today. Been like that since 1972. Only
    in the last 5 years or so has sheet steel been available in true metric!
    Well, mechanical engineering is a bit different; you can't put a 1" shaft
    into a 25mm bearing, no matter how hard you hit it!
     
    B. W. Salt., Nov 30, 2004
    #10
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