Offline question - on engineering standard scale

[jnanesh.sajjan]

Hi all,



This is not related to Pro-E though....but has some relation!



We have the standard engineering scales (1:1, 1:2....etc). I believe
these scales were made standard and were in practice when our previous
generation used to do manual drafting using those standard scales
(physical scales made with scaled fractions)



Now, question is: When we are using CAD drafting, is it really necessary
to go only with standard scales?









Thanks & Regards,



Jnanesha KS



T 91-80-4119 0900 Ext: 466

F 91-80-41190901
M 994 500 4179
-



www.quest-global.com

[jnanesh.sajjan]

Ok...it creates problems some time. Anyways, thanks for the reply.



Ben - I replied to you but it bounced back.





Thanks & Regards,



Jnanesha KS



T 91-80-4119 0900 Ext: 466

F 91-80-41190901
M 994 500 4179
-



www.quest-global.com

[dgallup]

ISO 5455 specifies the standard scales of 1, 2, 5, 10, etc. but qualifies them with the note:

"In exceptional cases where for functional reasons the recommended scales cannot be applied, intermediate scales may be chosen."

Because everyone here views & prints drawing on A or B size paper, we try to avoid using large drawing sheet sizes. An E size drawing printed out on B size paper is nearly illegible. In my quest to use the largest scale on the smallest sheet size I have taken to using 4 & 8 as well as the standards sizes. In addition, on detail views I have occasionally used 25 (we make some really small parts). My rationalization is that those scales are still multiples of 2, 5 & 10.

I would never use any scale whose reciprocal is an irrational number like 3 or 7.

[NEALROSENBLUM]

Jnanesha,



I am no standards guru. Over the years though, I have almost always seen
drawings with nice numbers like 2x, 4x, 8x, etc. I haven't seen many
drawings with 2.5x, 3x, 6x, etc.



That being said, I think that one rule should supersede another rule and
that is to provide the most legible drawing possible in order to avoid
confusion and/or misinterpretation. Therefore, I say go ahead and use
"off-scale" numbers. Don't go too far out like 3.5x, but I say provide a
legible drawing as a first priority and then worry about the scale.



By the way, I place a note (part of my format) in the title block of every
drawing that states, "DO NOT SCALE." This basically means that anybody
reading the drawing should not try to take measurements from the drawing
(even though my drawings are created from the models and I have used "shown"
dimensions). I think that this is a good practice, especially when the
scale is not easily divisible by 2. In fact, "divisibility by 2" was
probably a big deal when designers used to create drawings with a pencil and
paper. Finally, most of my customers use the 3D data to fabricate the parts
and they use the drawings to check the parts.





Sincerely,

Neal Rosenblum

Geometrix Engineering, Inc.

201 N. 13th Avenue

Hollywood, FL 33019

[ptc-936529]

Being that companies are actually making a drawing and printing it out means that people have to use and read the drawing without the aid of a computer or pdf file.  Not that I endorse scaling drawings but engineers scales and architects scales are still out there and being used.    I see little point in scaling a view to 37/100 scale, if you need calipers, dividers and a calculator to check a dim on a drawing.....I suggest putting in the title block "Not to Scale".

Just my $.02


----------

[dgschaefer]

I'm of the mind that fractional scales should be logical. Don't use 1/3
or 3/8. Larger scales, I think anything is OK 2x, 3x, 4x, 5x, etc.

All of our drawings, as any mechanical drawing should, say 'Do not
scale', however I want it to be scalable, which is why I use what I call
logical fractional scales (1/2 or 1/4 mostly)

The reason being, if a molder has an IGES file on screen and he takes a
measurement that doesn't seem to make sense, he can print the drawing
PDF and measure it to verify that the IGES is telling him. If there's a
conflict, the IGES should win (or better yet, he should call me), but it
helps him perform a sanity check (Is that really 3"?!? Huh, look at
that, 3" on the print too.)

The reality is that, as someone mentioned, none of our prints get
plotted full scale anymore. The vendor gets sent a PDF and the biggest
printer he has is likely 11 x 17 (B size). So, we try to do all of our
drawings on C size formats, if needed we'll go to D size. We don't use
A or B size because they're just too small to get much information in.

Doug Schaefer

[jflores-3]

Hey Jnanesha,

I believe that today the scale of your drawings is dependent on your
drafting room manual, not the drafting standards. Today the standards
are more in line with Neal's comments. The following is what is in the
2004 version of ASMEY14.100 (engineering drawing practices).







Para 4.23.3 refers to views not drawing not to scale.



I believe the old practice also specified that if your drawing was in
inches the scale note should be expressed in fractions and if in
millimeter it should be expressed as a ratio. This 2004 version allows
fractions, ratio or decimal regardless of the drawing units.



Being old school I tend to go along with Doug's practice and for the
most part stick to what he refers to as logical fractions except for
large exploded views when I use what ever scale get me to the edges of
the drawing border. Although my drawings say DO NOT SCALE, I still
create full size PDF's so that if needed, the supplier has the option of
printing a full size hard copy or printing it at a B size.



Thank you, Jim Flores

Mech. designer/CAD admin.

Clinical Care Systems

Philips Healthcare

2271 Cosmos Court

Carlsbad, CA. 92011

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[SteveFowler]

Back in a previous life in a tool design shop I scaled drawings now and again. Slap a scale on a known dimension and pull out the calculator. Nothing I ever received was printed to any scale anyway, that's what dimensions are for. We also put everything on a C sheet so it prints readable on a B printer. I believe prints are more scalable now than ever before. I however pay absolutely NO attention to what the drawing scale says, Just make the views as large as possible for clarity.

Just my opinion

Thanks

Steve

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