Datums To Show Orientation
Datums To Show Orientation
(OP)
Is there any precedence for using Datums on a drawing simply to show the orientation of a part?
First off, know that the man in charge where I work has deemed it appropriate to only use A size sheets on all drawings. Because of this, some additional sheets are often necessary to fully describe our parts. In some cases, a sheet will show only one view. For the part in question, this fact could cause confusion because it is nearly symmetrical.
My initial thought is that showing section view arrows on another sheet that reference the sheet and view in question is a simple way to describe the orientation of the part.
I also thought that showing hidden lines could clear the confusion, as I've stated before, the part is nearly symmetrical and doing this doesn't really solve anything.
Another idea would be to use Datums on every sheet (even though they're not needed functionally) to show orientation. Would this even be allowed under Y14.5?
Opinions?
Thanks,
Mod
First off, know that the man in charge where I work has deemed it appropriate to only use A size sheets on all drawings. Because of this, some additional sheets are often necessary to fully describe our parts. In some cases, a sheet will show only one view. For the part in question, this fact could cause confusion because it is nearly symmetrical.
My initial thought is that showing section view arrows on another sheet that reference the sheet and view in question is a simple way to describe the orientation of the part.
I also thought that showing hidden lines could clear the confusion, as I've stated before, the part is nearly symmetrical and doing this doesn't really solve anything.
Another idea would be to use Datums on every sheet (even though they're not needed functionally) to show orientation. Would this even be allowed under Y14.5?
Opinions?
Thanks,
Mod





RE: Datums To Show Orientation
This is the letter-of-the-law interpretation. But let's see what the other folks have to say...
John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems
http://www.gdtseminars.com
RE: Datums To Show Orientation
Repeating datum identifiers (obviously to the same feature but you hopefully get my point) on different views is acceptable. I wouldn't normally do it unless they are actually being used in that view though.
Trouble is by mandating use of A sheets only, a lot of the standard practices on drawing layout issues will be difficult to apply since one of the fundamental rules is where possible you draw at 1:1 and only scale when necessary. Minimum text sizes are 3mm etc, and with a marginally standard title & rev block there isn't going to be much real estate.
What is Engineering anyway: FAQ1088-1484: In layman terms, what is "engineering"?
RE: Datums To Show Orientation
Matt Lorono
CAD Engineer/ECN Analyst
Silicon Valley, CA
Lorono's SolidWorks Resources
Co-moderator of Solidworks Yahoo! Group
and Mechnical.Engineering Yahoo! Group
RE: Datums To Show Orientation
This is a simple example of how I'd probably do it, based on Figure 9 of 14.3 and text in section 1.7. I've been taught that when the removed view isn't on the same sheet add the sheet number next to the view label as I've shown. It's not explicitly in the standard that I see but is probably good practice.
What is Engineering anyway: FAQ1088-1484: In layman terms, what is "engineering"?
RE: Datums To Show Orientation
I don't like seeing datum identifiers on a drawing unless they're being used in a FCF somewhere.
RE: Datums To Show Orientation
Thanks.
RE: Datums To Show Orientation
RE: Datums To Show Orientation
Better to reduce the scale on the overall drawing showing adjacent views sufficient to establish the orientation, and show enlarged detail views to show the part detail. Othewise show sectioned or explicit views with cutting planes.
Drawings on multiple sheets is established practice many places. And a 1:1 scale may sound like a good idea, but not very workable if you make tiny fasteners or are in the ship building business.
Though repeating datum callouts on removed views and the original view is allowable, it's bad practice when you're trying to control configurations. If a change is needed, and you don't make the same change twice, your drawing is no longer subject to one interpretation.
RE: Datums To Show Orientation
RE: Datums To Show Orientation
As to your comments about boats, obviously you aren't familiar with where the term lofting came from
What is Engineering anyway: FAQ1088-1484: In layman terms, what is "engineering"?
RE: Datums To Show Orientation
The GD&T Standards, if I'm not mistaken, simply require that it be to scale with a few exceptions. I've often dealt with the machining of 80-inch ball valves and 120 inch diameter pump covers. 1:1 doesn't work. Of course if I had to do that on A sheets it would be quite a lot of them, and would be very difficult to do given the requirement for text readability.
At my work, we used almost exclusively B sheets. Given my 'druthers I would have liked to use something like an E sheet. We did it -- and the drawings were clear.
You are, however, prone to "page-switch-related" errors when manufacturing the parts. In the example described above, it seems that Mod is worried about this type of error.