Scale confusion ... again

[ReMark]

Contractors should NOT be scaling off a drawing. In your case the contractor should refer to the cable schedule. It is in his best interest to do so. If there is an error he can always point to the schedule and say that he used the information that was provided by the design firm. If he decides to scale a drawing and there is an error then the fault lies with him. Or is that what your firm is counting on? The blame game lives on.

[Tiger]

Yes, contractors SHOULD take their measurements from the correct place, a list, a dimension, what have you. But if weknow that they do not always do that (I have seen my contractors whip out the carpenters ruler and measure on my half-scale A3...*shudders*) isn't it in our best interest to make sure that the drawings are plotted at the correct scale?

[SLW210]

Contractors should NOT be scaling off a drawing. In your case the contractor should refer to the cable schedule. It is in his best interest to do so. If there is an error he can always point to the schedule and say that he used the information that was provided by the design firm. If he decides to scale a drawing and there is an error then the fault lies with him. Or is that what your firm is counting on? The blame game lives on.

 

1.) This warrants repeating, as another insurance, you should set up for any PDFs a Watermark or similar stating "Do Not Scale Drawing" or words to that effect.

 

2.) Your problem most likely stems from a double border situation. You plot from AutoCAD to PDF and a border is created around the actual drawing area, then you plot the PDF which also creates a border around what it perceives as the printable area, which includes the previous border. Sometimes, if the borders are the same, "fit to page" will eliminate the second border or if the plotter allows, maybe set the borders to 0. That is why your scale is off an even amount, the borders are even amounts.

[SLW210]

Yes, contractors SHOULD take their measurements from the correct place, a list, a dimension, what have you. But if weknow that they do not always do that (I have seen my contractors whip out the carpenters ruler and measure on my half-scale A3...*shudders*) isn't it in our best interest to make sure that the drawings are plotted at the correct scale?

 

No, it is in the contractors best interest to use correct dimensions. If the contractor desires to scale a drawing to find a dimension, it is in his best interest to determine the actual scale, not what is noted on the drawing.

[ReMark]

Anything scaled off of a drawing should be assumed to be a ballpark figure and not an 100% accurate dimension. Caveat emptor.

[Tiger]

No, it is in the contractors best interest to use correct dimensions. If the contractor desires to scale a drawing to find a dimension, it is in his best interest to determine the actual scale, not what is noted on the drawing.

 

And its not in our as in designer/drafters best interest to present a correct drawing?

[ReMark]

I'm not advocating that the drawing shouldn't be correct. One should build off a correctly dimensioned drawing; one shouldn't be scaling off a drawing to build.

[Tiger]

I'm not advocating that the drawing shouldn't be correct. One should build off a correctly dimensioned drawing; one shouldn't be scaling off a drawing to build.

 

And that is something we as designers can't do a damn thing about.

[ReMark]

I entirely agree with your last statement. Unless of course rulers and scales are banned! LOL

 

I wonder if the Egyptians built the pyramids off of drawings done to scale or scaled off the drawings?

[SLW210]

And its not in our as in designer/drafters best interest to present a correct DRAWING?

 

Keyword DRAWING not PDFs or plots.

 

What if in the above situation a properly scaled DWG file was sent and the contractor was plotting it to PDF or to the plotter? Do you feel that the draftsman is responsible for the accuracy? What if it was set to plot A size, but the contractor plots it at D size?

[SLW210]

I entirely agree with your last statement. Unless of course rulers and scales are banned! LOL

 

I wonder if the Egyptians built the pyramids off of drawings done to scale or scaled off the drawings?

 

Everyone knows that aliens and machines from the future built the pyramids.

 

So you tell us.

[ReMark]

We used modern methods. A hologram of the pyramid was constructed over the site and the Egyptians filled it in with blocks of stone. Who needs CAD? That's really ancient by our standards.

[Tiger]

Keyword DRAWING not PDFs or plots.

 

What if in the above situation a properly scaled DWG file was sent and the contractor was plotting it to PDF or to the plotter? Do you feel that the draftsman is responsible for the accuracy? What if it was set to plot A size, but the contractor plots it at D size?

 

I believe the draughtsman is responsible for what he delivers, when he delivers it - not what others do with that material without his consent.

 

Not that the contracters care, they will blame the draughtsman either way. C'est la vie.

[Jack_O'neill]

When it boils right down to it, the missing dimensions should be found long before it gets to a contractor's hands. I understand that checking drawings takes up valuable time, and a lot of companies have gotten away from doing it because of that. You've got to wonder though what the logic is behind that, when a missing dimension can cause thousands of dollars in back charges for lost labor and materials. Nobody is perfect, and errors and omissions happen, but a second or even third set of eyes on a drawing might find when these critical dimensions aren't there before you have a crew that costs $10,000 an hour sitting idle while someone starts the chain of phone calls to get it, or a contractor pulls out a tape measure and tries to figure it out for himself.

 

It really doesn't matter what scale it's originally plotted at, chances are the guy in the field that finds the missing dimension is working off a set that was not plotted as intended, and most likely has been reduced and been passed through 3 or 4 different copiers before it got to him. Depending on the quality of the copier and the individual settings of those copiers, the numbers in the SCALE: box are meaningless and probably shouldn't be there unless qualified that they apply only if printed on a particular size paper. Even then, the method of reproduction may skew the actual size of the drawing. Your brand x plotter may be perfect, but the GC's brand y copier may have wider margins and "shrink to fit" as the default. Let a speck or a coffee ring show up near the edge and it just gets worse. And heaven help you if someone runs a "reference" set off on the printer/copier in the trailer at the jobsite. Original was 36 x 48, but the biggest paper it uses is 11 x 17. I know, they are not supposed to do that, and they know it too, but it happens anyway.

[MisterJingles]

Ok I really have opened a can of worms here haven't I?

 

I feel contractors need a correctly scaled drawing because whether they should or not, someone WILL use a plotted drawing to take a measurement at some point, even if to aid a discussion.

And as mentioned, if they do and there is a discrepancy, it will be my head they come for.

 

I need to know what the best way to do about distributing soft copy drawings is in future.

If I send a PDF around is it not perhaps best to include a note or watermark as mentioned, stating something along the lines of "PDF drawing may not be scaled correctly. Please double check measurements"?

Seems to me that unless I am the one plotting the drawing this is the only way to go.

[Organic]

The design drawings should have critical dimensions shown and be plotted (and pdfed) to scale for the contractor in my opinion. It is unrealistic to provide dimensions for all parts of a plan and some interpretation is often required by the site engineer or contractor.

[ReMark]

The design drawings should have critical dimensions shown and be plotted (and pdfed) to scale for the contractor in my opinion. It is unrealistic to provide dimensions for all parts of a plan and some interpretation is often required by the site engineer or contractor.

Some interpretation? That's like a license to screw up and blame someone else. LOL

 

Thomas E. French, in his book "Engineering Drawing", writes, "...he (the engineering draftsman) may not depend on suggested meanings but must give precise and positive information regarding every detail of the machine or structure..."

 

I agree with you Dink re: critical dimensions. But there should be no doubt what our intentions are. If there is it is incumbent upon the contractor to pick up the phone, fax, email, or use whatever means is at his disposal to obtain any missing information. There is no excuse to do otherwise in my opinion.

Edited March 3, 2011 by ReMark

[Jack_O'neill]

Ok I really have opened a can of worms here haven't I?

 

Not at all. This is good healthy discussion. It is a positive thing when many points of view are presented. It opens everyone's mind to new possibilities and experiences beyond thier own. We all have a piece of this pie and need to work towards solutions that we can all take and adapt to our respective applications.

 

One thing that hasn't been addressed in this discussion however, is the question of how much precision is actually needed? For instance, the guys pouring the "stones" as the are called for the Hoover Dam Bridge were required to work concrete to a few thousandths of an inch. This is venturing into machine shop tolerances. At the opposite end, I've worked with contractors that thought if they poured in the right town it was close enough. Can't tell you how many times I've had to revise curtain wall drawings because the openings just didn't come out the right size for some reason. This is a real problem if you've fabricated the frames and bought glass already. Sometimes you can rework the frames, sometimes you can't. If the glass is wrong, it's scrap. Laminated, insulated glass can not be cut down once its been produced. If the opening in the building is off by more than the tolerances in the curtainwall will make up for, you've just thrown many thousands of dollars in the recycle bin. So how close do we really need to work?

[ReMark]

The only time one should be scaling off a print to build something is when they are constructing a horseshoe pit. For as we all know "close enough" counts in horseshoes!

[Jack_O'neill]

The only time one should be scaling off a print to build something is when they are constructing a horseshoe pit. For as we all know "close enough" counts in horseshoes!

 

You got that right. Many years ago I picked up a few extra bucks helping my brother-in-law build chicken houses. Yes, I said chicken houses...this is Arkansas, after all. At any rate, we were at a site that had 4 new ones going up, and were standing steel trusses. As we worked our way down the length of the footing, it began to get difficult to get them over the bolts in the concrete. Application of a few pry bars and a big hammer corrected for some of it as we cussed the guy that put the bolts in. Three of the four had gone without a hitch, so comments were made about the guy having got tired or drunk or whatever. We finally hit a point where we could not correct for it. Measured the truss, it was in tolerance, so I finally went to the truck and got a 100 ft. tape and checked the footing. It was supposed to be 50' x 500'. It was 50' at the end we started on, but only about 46' at the opposite end. After several angry phone calls, many trips to the site with the concrete guys, one fist fight and many hours of listening to a jack hammer bust up the footing, a week or so later we resumed standing trusses.