Simple Question about Centerlines
Simple Question about Centerlines
(OP)
A little embarrassed that I don't know this by now, but is there a section in the standard (2009) that explains when and when not to use a centerline on a detail drawing? Specifically, one that passes through the entire part? I know you would do this anytime you would be detailing a round part, but what about a square part with angles and bosses and such. If the part is symmetrical, is it common to always place a centerline along the length of it when looking at it from a view that shows that symmetry? Even if you're not using a CL symbol or invoking any symmetry controls?
I ask because I've got a jumbled mess of a part with all of it's cuts and angles in plan view, but from above, it is indeed the same on both sides. Is this a standard thing to place a CL on those views? Or is it perhaps just tribal knowledge for some?
Thanks. I want to sit for the GDTP in 9-12 months and I need to figure all of this minutiae out.
Mike
I ask because I've got a jumbled mess of a part with all of it's cuts and angles in plan view, but from above, it is indeed the same on both sides. Is this a standard thing to place a CL on those views? Or is it perhaps just tribal knowledge for some?
Thanks. I want to sit for the GDTP in 9-12 months and I need to figure all of this minutiae out.
Mike
I'm not a vegetarian because I dislike meat... I'm a vegetarian because I HATE plants!!





RE: Simple Question about Centerlines
It looks more like domain of Y14.2 Lines and Lettering and Y14.3 Views and Sections.
I've never seen standard explicitly stating when to use centerline and when not to.
Also most of the people will agree that CL is not a standard symbol, so don’t worry about that as well.
Centerlines sometimes perform specific functions, like for example in Symmetrical outlines (see Para. 1.8.9 / Fig. 1.35 in Y14.5-2009) obviously; centerline has to be shown in such cases.
Nobody opposes using centerline on round holes / shafts, etc.
Now to your case of part which is “symmetrical, but not exactly”. To me it appears as a matter of personal preference and should be judged on case-by-case basis.
For example, as a matter of my personal preference, when I use datum symbol aligned with FOS dimension (which we both know means that datum is actually center plane / axis) I draw the center line to indicate where said plane / axis actually is.
Just ask yourself if centerline will make things more clear or obscure.
Naturally I am very much interested to see other opinions.
PS. And good luck on your exam!
RE: Simple Question about Centerlines
Please enumerate on the section of the standard you are refereing to!
Frank
RE: Simple Question about Centerlines
One could argue that if not helping define/detail the part it's just extra clutter that doesn't need to be on the drawing.
What is Engineering anyway: FAQ1088-1484: In layman terms, what is "engineering"?
RE: Simple Question about Centerlines
RE: Simple Question about Centerlines
Tunalover
RE: Simple Question about Centerlines
RE: Simple Question about Centerlines
John Acosta, GDTP S-0731
Engineering Technician
Inventor 2013
Mastercam X6
Smartcam 11.1
SSG, U.S. Army
Taji, Iraq OIF II
RE: Simple Question about Centerlines
What is Engineering anyway: FAQ1088-1484: In layman terms, what is "engineering"?
RE: Simple Question about Centerlines
RE: Simple Question about Centerlines
Tunalover
RE: Simple Question about Centerlines
John Acosta, GDTP S-0731
Engineering Technician
Inventor 2013
Mastercam X6
Smartcam 11.1
SSG, U.S. Army
Taji, Iraq OIF II