Both DO NOT SCALE and SCALE in title block 3

[bxbzq]

I recently going through some drawings that in title block it has a cell stating DO NOT SCALE, while another cell in the title block showing scale number under the SCALE subtitle. Does it make sense?

 

[MikeHalloran]

It used to be dangerous to scale drawings because a contact print (like a diazo) could grow or shrink by a couple of percent that you might not notice until the parts didn't fit.

Nowadays it's even more dangerous because of uncalibrated noncontact printers, and because of the number of electronic shrink/stretch cycles an image may have undergone to fit various virtual pages before it ever reaches you.

The SCALE number tells you how a linear dimension on the image you've got corresponds to the linear dimension on the real drawing. ... but you may have to guess what size the real drawing is, or use other dimensions in order to evaluate the real transfer function.

IOW:
You assume some risk by scaling from a drawing, and more so in recent decades. A general scale factor is provided as a courtesy. DO NOT SCALE makes it clear that the risk is yours alone.






Mike Halloran
Pembroke Pines, FL, USA

 

[drawoh]

MikeHalloran,

In SolidWorks, you can select the appropriate paper size, and forget to de-select scale-to-fit.

When I want people to scale my drawings, I attach a reference scale on my titleblock. Someone can take a ruler, and check my drawing's scale.

--
JHG

 

[MikeHalloran]

A while back, I was making paper templates for cutting intersections in large tubes, and for cutting the actual blanks for things like cones.

We had a few instances of plots being scaled wrong along the way, and the mistakes were expensive because we were using nickel alloys that cost $1000 or more per sheet.

So I got in the habit of putting a prominent line on each template image, with an equally prominent dimension. Whoever did the plot and cut the template also measured that line to verify that it was the correct size, and initialed the dimension line on the template to say so.



Mike Halloran
Pembroke Pines, FL, USA

 

[TheTick]

NEVER scale a drawing.

If you must scale a drawing, check a measurement against a known dimension in the drawing. Better if you check both horizontal and vertical scaling.

90+% of drafting nowadays is careless slopsmanship. Always verify.

 

[Belanger]

The Scale thing by itself just tells the proportion of the picture you're looking at relative to the real part. So that cell might say "2:1" which means that the picture is twice the size of the real part.

I think it's OK that the print also says Do Not Scale, because as mentioned above that just instructs you not to rely on actual measurements from the print. Yes, in the "old days" people would sometimes literally put a ruler up to the print and try to determine the real build size from that!

John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems

 

[berkshire]

Mike said,
So I got in the habit of putting a prominent line on each template image, with an equally prominent dimension. Whoever did the plot and cut the template also measured that line to verify that it was the correct size, and initialed the dimension line on the template to say so.

I have fallen into that booby trap of not having parts cut at the correct scale when sending water-jet patterns. So now we always put a rule, or a 1" square on the plot to be checked before the actual cut.
B.E.

You are judged not by what you know, but by what you can do.

 

[MikeHalloran]

>>>So now we always put a rule, or a 1" square on the plot to be checked before the actual cut.<<<

Great idea; include an image of a simple 6" rule or other useful object, with a simplified logo, in a scrap area next to the part. Easy scale check, and you can pass them out at trade shows.




Mike Halloran
Pembroke Pines, FL, USA

 

[ewh]

"DO NOT SCALE" is a directive to not actually measure from the print. Other than full size mylar or silk drawings, paper drawings do not hold their accuracy - shrinking or growing depending on environmental variables and therefore not always accurate.
The drawing scale simply states the size of the views relative to each other and to the format size.
Different animals.

“Know the rules well, so you can break them effectively.”
-Dalai Lama XIV

 

[dgallup]

While I agree with all the above about paper not being dimensionally stable and printers not being calibrated, I think those errors pale in comparison to the drawing practices of past decades before solid modeling.

Back in the days of hand drawings and even a lot of sloppy AutoMAD drafting, dimensions were changed without redrawing the geometry. This was doubly true for assembly drawings. So many of the views were not drawn correctly and if you tried to measure directly off the drawing you could get a LARGE error. Our pre-printed mylar drawing sheets in those days would always have a note of DO NOT SCALE.

We no longer have that note in our drawing blocks for Pro/ENGINEER and SolidWorks generated drawings. Not saying that a draftsperson still can't fake something but they have to do extra work rather than just being lazy.

Our drawing blocks still have the microfilming center tick marks and a 100 mm linear scale. Does anyone else still remember the Gerber variable scales we used to use to scale things off drawings despite the DO NOT SCALE note? I guess those are relegated to the museums along with the slide rules.

----------------------------------------

The Help for this program was created in Windows Help format, which depends on a feature that isn't included in this version of Windows.

 

[ewh]

No, but I still have a pair of proportional dividers that I used for that purpose.

“Know the rules well, so you can break them effectively.”
-Dalai Lama XIV

 

[MintJulep]

Considering the ease that a drawing can be printed on the "wrong" size paper now, listing "Scale" in the title block seems pretty pointless.

A graphic scale makes more sense.

 

[CheckerHater]

Standard title block normally contains (amongst others) two fields: Scale and Sheet Size. Two of them together define CORRECT printer settings. “It was easy to print on business card stock” is not an excuse.
So the complete message delivered by title block is: IF your drawing is created to scale, and IF you set your printer correctly, the item will be shown scaled as noted, BUT don’t scale it anyway, just in case.

 

[KENAT]

So to the OP yes having both makes perfect sense.

The "SCALE" is telling you what scale the drawing was made at.

"DO NOT SCALE" is an instruction to users not to measure from the print.

At a former employer out template did have a reference scale on it showing 100mm or whatever like on a map but really you need something for both X & Y due to the potential different scale on the 2 axis from printing etc.

Posting guidelines faq731-376

http://eng-tips.com/market.cfm?

(probably not aimed specifically at you)
What is Engineering anyway: faq1088-1484​