standard drawing scales 8

[KENAT]

Quick and easy one (I hope) which ASME standard says to only use 1:2, 1:1, 2:1 etc. I'm sure I've found it before but can't recal where.

I have a couple of prints with scales like 3:2 and one that seems to be about 1.25:1. I think they've done this in part to cram it onto a B size sheet rather than use something larger. At least one of the engineers in question is difficult to deal with so I want to make sure I'm on firm ground.

I'm not (I hope) just being pedantic but the drawings are pretty cramped and I want to use this as another factor to persuade them to use a larger sheet size.

Thanks,

Ken

KENAT, probably the least qualified checker you'll ever meet...

 

[btrueblood]

Camelot!
(It's only a model)
ssh!

 

[CheckerRon]

btrueblood and ctopher:

Who cares about your 1/1 model? It doesn't do much for a crammed up (or maybe I should use 2p's) B size draft file.

This is KENAT's problem and I know where he's coming from.

 

[weavedreamer]

The fun can really begin when they reduce those roll size drawings to 8.5" X 11" or 11" X Roll Length / Scale Factor. It makes reading Fun-duh-mental.

 

[btrueblood]

"My main concern isn't so much that they are using weird scales, though I think it's bad practice, but that they are doing this to cram information onto a B size sheet rather than use a larger drawing."

Fine, so tell them so. A cluttered print is a cluttered print, and adding sheets is not a no-no in your system, is it? I tend to avoid huge sheet sizes, because many shops will print them or photocopy them to reduced sizes (A or B), and everything then becomes un-readable, regardless of how artistically I placed my views and callouts.

"Who cares about your 1/1 model? It doesn't do much for a crammed up (or maybe I should use 2p's) B size draft file."

See above. A whacked-out scale may be just what is needed to make certain features stand out. And if not, I put detail views on sheet #2, in whatever scale the CAD system says they are in, but re-lable the scale as "2X" or whatever. Then I put a note on the drawing "DO NOT SCALE FROM PRINT". And put "NONE" in the scale block. Who cares, as long as the scale relationships between views is maintained. I agree, a crapped-up drawing is a crapped up drawing, but the scale doesn't matter for that. And if I ever catch some old fossil using a scale on my paper CAD drawing, with those notes above added, he and I will have a discussion.

 

[KENAT]

btrue, we have some parts that are fairly complex. To draw them on B or even C is virtually impractical. They have so many dimensions that it becomes an incoherent mess.

If you try to do it on a B you end up with 2 or more of the same view, each on different sheets, to fit all the dimensions. While occasionally unavoidable I think having the same view several times doesn't seem like good practice and going by some of the drawings I've seen it on it's almost always difficult to understand. I've seen I think it was 5 or 6 sheet B size drawing that looked like a bowl of spaggeti or a spiders web, so many lines. A colleague & I redrew it on E as I recall on a single sheet, that was a lot clearer.

I believe, and was taught, that fewer large sheets are preferabl to lots of small sheets. If the machine shop can't handle the larger prints then they shouldn't accept the job. However, to mitigate this we have our font size set to .15" rather than the minimum 3mm so it's pretty clear when reduced.

Anyway btrue, seems you'd side with them on this one, always useful to have the opposite view point. They will talk about machine shops not having large plotters etc.

The reason I wanted the scale to back me up is that they don't care how bad their drawings look and will argue any changes I request so I like to have as much amunition and make sure I'm correct before I approach them.

KENAT, probably the least qualified checker you'll ever meet...

 

[WHITMIREGT]

I agree with btrueblood. The scale is not important, the data is. I require the lettering to be large enough when reduced to a "B" size, and change all colors to black when the drawing is released so that it is easy to read when reduced. Having more than one sheet to convey the engineering information is OK.

 

[ctopher]

I always use standard scales. I will start thinking about a B size dwg, if the views will not fit, I go to C size and so on. I will not use multiple sheets until I get to D size. This limits the amount of sheets to work with.

Chris
SolidWorks 07 4.0/PDMWorks 07
AutoCAD 06
ctopher's home (updated 10-07-07)
ctopher's blog

 

[KENAT]

So I accept that I was recalling incorrectly and none of the standards we explicitly invoke give scale preferences.

I have no arguement that more than one sheet is OK, however I think that one large sheet is better than multiple small sheets.

Glad I'm not the only one Ctopher, I was seriously starting to doubt myself.

When I said "how bad their drawings look" I meant as in regard to being difficult to read/incoherent/ambiguous. I did not mean that every drawing should be so beautiful you can frame it and put it on your wall!

KENAT, probably the least qualified checker you'll ever meet...

 

[ewh]

We tend to use larger format sizes for our drawings to keep them uncluttered and easy to understand. That said, when they are released, they are printed to a B size (no facilities for drawing storage). This is the official released document. We send our vendors cgm's of the drawings, which can be plotted full size if they wish. Since most of our products involve lofted bodies, the vendors are required to also reference the solid model. The biggest problem we have come across with this system is signing off the drawings in those tiny boxes

As far as the scales we use, I have a very difficult time letting go of those that used to be "preferred", even though I realize that I don't really have a legimate reason for correcting drawings that use a "non-preferred" scale.

 

[fcsuper]

As far as cramming parts onto inappropriately small drawings goes (in CAD), I simply never made an A size or B size drawing template at my company. If some new-comer asks for those sizes, I simply say "C prints to A and D prints to B". That usually settles it. If more explanation is required, I say, "Since most printouts are to A size and B size, all the smaller size formats give you is less space on the drawing because more of it is occupied by the title block." The advantage being that they have more room to detail their parts on a single sheet. If part scale is an issue, it takes no more effort to set the drawing scale appropriately in one size over another since the CAD package we use sets the ideal scale automatically (and usually it's right) regardless of sheet size.

Matt
CAD Engineer/ECN Analyst
Silicon Valley, CA
sw.fcsuper.com
Co-moderator of Solidworks Yahoo! Group

 

[btrueblood]

Kenat,

A drawing that is ambiguous, difficult to read, or incoherent doesn't need any other argument from you. I spend way too much time cleaning up older prints around here, and know what you mean. I say again, there is nothing wrong with multipe representations of the same view, as long as you are careful not to "double dimension". We have a lot of small parts with lots of goofy details, and getting all of the details called out from one view would crowd the drawing with arrow heads and leader lines. When I do put details or aux. views on seperate sheets, I reference the new sheet on the view callout, and add a note such as "(FROM SHT. X)" on the view label. Not a requirement, but helps the reader.