Quick drafting scaling question

I am trying to convert scales of drawings and photocopies. I wonder if anyone can help.

 

I'd like to transfer a 2200mm line which is on an A3 sheet at 1:100 to an A4 sheet which is a photocopy of a drawing that was originally A3 at 1:100.

 

What scale rule should I use to draw the representation of the original 2200mm line on the A4 photocopy?

The line should scale to 22 mm with a normal metric 1:1 rule, 2200 mm with a 1:100 rule. How do you see anything smaller than a meter at 1:100 anyway?

 

Wait. Is the photocopy reduced? If so, it is nearly impossible without knowing exactly what the reduction percentage is.

Wait. Is the photocopy reduced? If so, it is nearly impossible without knowing exactly what the reduction percentage is.

Yeah, it has to be a reduction. You need to measure a known line on the photocopy and compare with the original A3 to make sure you use the right scale reduction. Hopefully, it will be a standard scale in both cases.

Yes it is a photocopied reduction which is annoying. I tried to measure a sample line on the A3 sheet and to compare it with its copy at the reduced size on A4.

 

On a 1:1 scale rule, the sample line on the A3 is 39.5mm (3950mm with the 1:100 scale);

 

On the reduced A4 sheet this line at 1:1 becomes 26mm

 

I am guessing that the new scale will be around 1:150 but I don't have this scale on my rules.

It's a simple conversion. Multiply the measurement on the A4 (26) by 1.52 to get the original A3 value (39.5).

Yeah, it sounds like there will be no useful scale rule for this purpose. The 1.52 comes from dividing 39.5 by 26 and rounding. 1.5192308 is a bit closer, but you won't be measuring to that precision. Since you are going from the A3 to the A4, you should divide your original 22mm (2200 @ 1:100 on the A3) by this number, which will give you 14.48mm, or about 14.5mm on the A4.

Actually, with the numbers you provided, the intended reduction was probably 2/3 (reciprocal of 1.5). So, just multiply the length of any line on the A3 by 2/3 to get the new length for the A4. At least you're working with an original scale of 1:100.

By now you might have scanned it to a bmp, inserted it in AutoCAD, traced it and scaled up the results. It's done all the time, if great precision is not required.

Thanks for the tips.

 

It is not something I will be doing on AutoCAD. My employer wanted me to draw a new boundary line in red pen on the A4 sheet. I wanted it to be fairly accurate as a lawyer or two will probably look at it at some stage!

Thanks for the tips.

 

It is not something I will be doing on AutoCAD. My employer wanted me to draw a new boundary line in red pen on the A4 sheet. I wanted it to be fairly accurate as a lawyer or two will probably look at it at some stage!

 

You're welcome. Are you going to be ready when the lawyers ask you on oath how you know the line is accurate? Have fun!

Thanks for the tips.

 

It is not something I will be doing on AutoCAD. My employer wanted me to draw a new boundary line in red pen on the A4 sheet. I wanted it to be fairly accurate as a lawyer or two will probably look at it at some stage!

 

Yes welcome again, of course. Oh, my. Real estate lawyers, my blood runs cold. Seriously though, I doubt if even one of those guys would give much credence to a line drawn on a photocopy of anything. I'd say, "Go ahead dude, lay that in front of a judge." ? But then, better safe.....

Yes welcome again, of course. Oh, my. Real estate lawyers, my blood runs cold. Seriously though, I doubt if even one of those guys would give much credence to a line drawn on a photocopy of anything. I'd say, "Go ahead dude, lay that in front of a judge." ? But then, better safe.....

Yeah; not sure a drawn line has to mean much by itself anyway--that's why they say "Do NOT scale drawing!";) BTW, Dana, I love that Yogi-ism. So many applications. What's really funny is when someone tells me, "I don't get it." Boy, have they lived a sheltered life! Or do they just obliviously keep repeating history?

I tried to delete a duplicate post, didn't work, overtyped it instead.

Yeah; not sure a drawn line has to mean much by itself anyway--that's why they say "Do NOT scale drawing!";) BTW, Dana, I love that Yogi-ism. So many applications. What's really funny is when someone tells me, "I don't get it." Boy, have they lived a sheltered life! Or do they just obliviously keep repeating history?

Yup, Yogi was the original Hipster. He could create accidentally Ironic misinterpretations at the drop of a hat.

couple things. standard reduction from A3 > A4 is a scale of 0.707. If you want to work on scanned images then you might like to look at raster editing software (either inside AutoCAD or standalone). I've been using WiseImage from CSoft (www.csoft.com) for 15+yrs. Really this is the best.

standard reduction from A3 > A4 is a scale of 0.707.

Really!? I suppose that might work for document purposes, but using half of the square root of 2 for a drawing scale conversion does not sound too appealing to me. Better not complain though, or they might stick you with a natural log conversion!