DescentBB

I am hoping some of you are machinists or have experience working off of production drawings.

We are having a bit of a discussion regarding whether or not to put the scale into a production drawing. Myself and others are opposed to it, while are director of engineering is in favor of it.

I always felt that scale didnâ??t belong on a fully dimensioned drawing because that was what the dimensions are for. Including a scale on the drawing may encourage the end user of the drawing to take measurements right off of the drawing. The problem with that is you donâ??t know what the reproductive quality of the rendering device (printer, plotter, etc) is. It may be sloppy, and what is marked at 1:1 on the drawing may in fact be anywhere from .95:1 to 1.05:1 compared to the real part.

In the days when parts were all hand drawn to a specified scale and measurements were taken right off of the drawing, scale was very important. Now that things are drawn on the computer I just donâ??t see the necessity of including the scale on the drawing, primarily because of the rendering issues. I believe that it adds confusion not clarity.

What are your thoughts?

Reminds me to an incident a couple years back. We needed a special date stamp. Since the local stamp maker would take a technical drawing we had our drawing department one made and sent it to the stamp maker. A few days later me and a coworker went to pick the stamp up at lunch break. the stamp was perfect, exactly like the drawing w/ one exception -- it was about a foot long "Oh, I thought that values were centimeters.." According to DIN you don't need to include units to the dimensions, it's all in mm unless otherwise marked. Interpreting mm as cm scales the thing up by a factor of 10

AFAIK the stamp still is in the office of my friend as a warning to think twice.

Moral: always include as many cues as possible to a drawing because the world is full of halfwits

LOL @ Gren. Man, that would make an awesome souvenir.

I never scale off a drawing. Only a fool would do that.

Hahahaha great one Grendel!

woodchip wrote:I never scale off a drawing. Only a fool would do that.

I agree. The question is should the scale be called out on the drawing or not?

My vote : Yes it should

You can scale the drawing, but put a symbol on it that says not to take measurements directly from the drawing but look at the dimensions instead. Ill show you later on today what I mean.

Dedman wrote:

woodchip wrote:I never scale off a drawing. Only a fool would do that.

I agree. The question is should the scale be called out on the drawing or not?

Typically on architectural drawings a scale is given which may be used for approximations. Dimensions are what one is held accountable to though. Even then I have a habit of adding up sub-dimensions to see that they equal what the over all dimension indicates. Sometimes measuring to scale will find what sub-dimension is not correct.

Well, I'm still just in school, but everything I print from AutoCad has the drawing scale on it.

scale = yes.

If people don't read the info on the drawing,
that's their problem when it turns out poorly.

I think things should be drawn to scale. It gives the machinist/assembler/welder an idea of how it should look at the end. 1:1 scale shouldn't be a problem either... I assume that your company has a QA dept... and only an idiot would think that they could get a hand measured part past QA inspection. Plus, if it's any sort of critical measurements, it will be in the thousandths, and will have a specified tolerance associated with it... considering that fact that your printed line is what... at least 10 thou wide only an idiot would try to machine something to within tolerance by eyeballing the drawing. Of course then, I'm sure it's been done... but that's the difference between a machinist with a job and one who is looking for one.

dissent wrote:If people don't read the info on the drawing,that's their problem when it turns out poorly.

If my company invests $60,000 in tooling and the tooling company builds it wrong because the drawing they used conflicted itself (which can easily happen when you specify scale on a fully dimensioned production drawing) then it very well could be my company's problem. We may end up paying $60,000 twice.

What purpose does specifying the scale on a fully dimensioned production drawing serve?

If the scaling is done true, and the CAD drawings are fed into a CAD CAM machine then everything is fine. You are assuming that the machine maker is going to take your paper drawings and essentially redraw the machine part into their cad program by hand using the listed dimensions?

This has nothing to do with entering the dimensional data of the part into a CAD CAM machine. If we needed to do that, we would input the CATIA model directly and the production drawing would primarily be for first article inspection.

What information (other than the scale itself) does calling out the scale of the drawing give the end user of the drawing that wouldn't be there if the scale weren't called out.

from what you've said dedman, it seems that a scale should only be included if accompanied by a disclaimer. otherwise it shouldn't be included.
your arguments make a lot of sense.

Dedman wrote:What information (other than the scale itself) does calling out the scale of the drawing give the end user of the drawing that wouldn't be there if the scale weren't called out.

the obvious? it may help in quickly visualising the actual size of the object at a glance.

roid wrote:the obvious? it may help in quickly visualising the actual size of the object at a glance.

Can't that be done by looking at the actual dimensions?

I think the use of a scale call out on a production drawing is a hold over from when drawings were done by hand onto velum and many dimensions were actually taken right off of the drawing. A few esoteric applications aside, that is an antiquated system that isn't used any longer.

just put "not to scale" on the drawing. In large letters. that should cover your buts enough.

Dedman wrote:

roid wrote:the obvious? it may help in quickly visualising the actual size of the object at a glance.

Can't that be done by looking at the actual dimensions?

at a glance, to the layman, a scale would be quicker.

actually something quicker again would be a small diagram showing the object next-to some other common object - for scale comparison.

Dedman wrote:
Can't that be done by looking at the actual dimensions?

Not unless the dimensions are drawn to some sort of scale.

Dimensions are dimensions. A 3inch diameter is a three inch diameter. If it appears to only be half an inch on the drawing, the dimension call out of 3 inches should tell you about how big it is. Don't you think?

Look at it this way. If it were hand drawn and if all the different components were on the same sheet of paper, the "Porportions" may not give a accurate idea of what you were building. Thus you could hav a 3" and a 6" diameter pipe as components but if they were just drawn as pipes that looked like they were the same size (even though they were labeled correctly) what you saw would not be a accurate rendition of how the two pipes were in relation to each other. Tough to visualise the end product, no?

woodchip wrote:Tough to visualise the end product, no?

Not really. And I am not talking about hand drawn drawings here.

Dedman wrote:

woodchip wrote:Tough to visualise the end product, no?

Not really. And I am not talking about hand drawn drawings here.

I was giving a worse case example. If you are using CAD then drawing to scale and dimensioning the drawing at the same time is pretty simple.