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Scaling drawings


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Guest Natalie Graham

Divide the dimensions by 7 and multiply by 4? ;)

 

 

 

Not as facetious as it sounds. I use a slide rule (who remembers them?) set to do just that and then it is simply a matter of taking the dimension and reading its equivalent form the slide rule.

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i have several scale drawings at 7mm/ft that i would like to scale down to 4mm/ft. does anybody know of a easy way to do this?

 

 

DJ,

 

divide the 7mm size by 1.75. eg 14 divided by 1.75 = 8. Or do you mean on a photocopier?

 

OzzyO.

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Hiya

 

Seriously? You cant work out what the relationship of 4mm scale to 7mm scale is as a percentage? I am hoping you just asked the question without trying to think of an answer yourself first. (hey - we have all been there wink.gif ) but you are a 21 yr old Mechanical engineer - what do they teach people these days? tongue.gif (where is the head banging smiley thing?)

 

(divide 100 by 7 - times by 4)

 

Cheers

 

Jim

 

 

Hi Jim,

 

I dont think that you can do it in one hit (one hit gives you 57.142856 on my calc), I seem to remember that you have to do in two gos some thing like 40% then 3%. You also have to watch that it has reduced by the same amount in the vertical and horizontal plains.

 

OzzyO.

 

But hey he should know that.

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On a photocopier or computer reduce the size to 67% - simples CHITCK!

 

Did you mean 57%? wink.gif

 

Assuming photoreduction, you need to be sure that the scale reduction is correct in both x and y directions.

 

Draw two scale bars on the drawings of a known dimension, say 10ft, at right angles to each other. In 7mm scale these will be 70mm long. Make them as long as practicable for better accuracy.

 

Take drawings to good copy shop where they have a photocopier with infinitely variable scaling, at least to the nearest 1%. Get them to demonstrate that they can photoreduce so that the lines you have drawn are now 40mm long (for the above example). If they can, to your satisfaction, pay them to do the others. If they can't, go somewhere else.

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