Quantity callouts
Quantity callouts
(OP)
Hello, I was wondering if some of you all might be able to clairify or perhaps share some "best practices" with respect to calling out quantities on engineering drawings when it comes to features (lets say holes) in a pattern.
Here is the confusion: In the GD+T standard, sections 1.9.5 and 1.9.5.1, a numeric callout of quantity "May" be used to indicate the number of features to which that dimension is applied. My interpretation of that is if, for example, I had a square 4-hole pattern (lets say 100 mm spacing in both the horizontal and vertical, I could either dimension it as 100 x 100 (basic of course) or 2x 100 x 2x 100 (again, basic), and either is technically correct.
But suppose I had multiple patterns with holes of various sizes laying on the same line? What then? What should I do if I have a number of holes of differing sizes which I'd still like to control as a pattern?
(See attached crude and hastily drawn sketch for clarification of what I'm asking)
Here is the confusion: In the GD+T standard, sections 1.9.5 and 1.9.5.1, a numeric callout of quantity "May" be used to indicate the number of features to which that dimension is applied. My interpretation of that is if, for example, I had a square 4-hole pattern (lets say 100 mm spacing in both the horizontal and vertical, I could either dimension it as 100 x 100 (basic of course) or 2x 100 x 2x 100 (again, basic), and either is technically correct.
But suppose I had multiple patterns with holes of various sizes laying on the same line? What then? What should I do if I have a number of holes of differing sizes which I'd still like to control as a pattern?
(See attached crude and hastily drawn sketch for clarification of what I'm asking)





RE: Quantity callouts
Good questions here! I will be really interested on what other people do in these situations.
I think what should be considered is not how many patterns you have but how many times the dimension is repeated.
Also when I have a serie of holes linked through centerlines as in you sketch, I do not usually add a multiplier.
2JL
RE: Quantity callouts
"Know the rules well, so you can break them effectively."
-Dalai Lama XIV
RE: Quantity callouts
2x 100 x 2x 100 works if you don't show common center-lines (but it's obvious the features are inline and hence what the '100' applies to)
It doesn't matter if the holes or other features are not identical so long as it's clear they are inline and so the '2X' dimension applies to them.
Likewise if using center-lines you can just put '100' and it applies to every feature on that common center-line regardless of individual feature size.
What is Engineering anyway: FAQ1088-1484: In layman terms, what is "engineering"?
RE: Quantity callouts
See, thats part of our confusion. Our design drafting department has been told numerous times from at least 2 different GD+T trainers/traning organizations that centerlines "Don't mean anything" - yet the standard itself does exactly what you propose. So do we trust the trainers, both of which are or have been on the GD+T committee, or do we trust the standard, understanding that the callout is optional? Are there times when it really shouldn't be optional?
RE: Quantity callouts
Center-lines in association with a position (or maybe surface profile) tolerance on the features of size that share that center-line (hence saying how far you can deviate from that center-line) does have meaning*.
I would say combining 2X with center-lines is confusing and shouldn't' be done at all - pick one or the other. Most illustrations in ASME Y14.5M-1994(for what they are worth) show center-lines but no '2X'. Quick flick & I didn't notice any that had 2X + center-lines.
[*There is also an option of a general note covering feature alignment but I don't want to muddy the waters here.]
What is Engineering anyway: FAQ1088-1484: In layman terms, what is "engineering"?
RE: Quantity callouts
I tend to think a bit more about it and pick either center-lines or '2X' depending on which will give a clearer less cluttered drawing.
What is Engineering anyway: FAQ1088-1484: In layman terms, what is "engineering"?
RE: Quantity callouts
"Know the rules well, so you can break them effectively."
-Dalai Lama XIV
RE: Quantity callouts
What is Engineering anyway: FAQ1088-1484: In layman terms, what is "engineering"?
RE: Quantity callouts
The only way to deal with the experts like that is to ask them to show, where exactly ASME Y14.5 book says that cenerlines don't mean anything
"For every expert there is an equal and opposite expert"
Arthur C. Clarke Profiles of the future
RE: Quantity callouts
John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems
RE: Quantity callouts
I have said it here before that, do to the simplified examples in the standard, things like this get missed and it is a headache for those of us out in the real world doing real parts if they do not.
Frank
RE: Quantity callouts
RE: Quantity callouts
And I'm not sure what you mean by "solid dimension extension lines." There are dimension lines and extension lines. (I think you mean the latter?)
John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems
RE: Quantity callouts
"Know the rules well, so you can break them effectively."
-Dalai Lama XIV
RE: Quantity callouts
At my work, however, I've been unable to get people to follow that because default dimensions in ProE always use solid extension lines, so it would require extra work.