×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

Quantity callouts

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)

RE: Quantity callouts

Hello

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

If your holes are in line and connected by a centerline, no quantity is needed. As in your example, you are dimensioning the distance between centerlines and to add a quantity would "muddy" the drawing. Even if there were one hundred holes on that centerline, no quantity is required to locate the centerline.

"Know the rules well, so you can break them effectively."
-Dalai Lama XIV

RE: Quantity callouts

100 x 100 works if you are showing common center-lines

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.

Posting guidelines FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm? (probably not aimed specifically at you)
What is Engineering anyway: FAQ1088-1484: In layman terms, what is "engineering"?

RE: Quantity callouts

(OP)

Quote (ewh)

If your holes are in line and connected by a centerline, no quantity is needed. As in your example, you are dimensioning the distance between centerlines and to add a quantity would "muddy" the drawing. Even if there were one hundred holes on that centerline, no quantity is required to locate the centerline.

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 by them selves do nothing (2.7.3 of ASME Y14.5M-1994).

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.]

Posting guidelines FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm? (probably not aimed specifically at you)
What is Engineering anyway: FAQ1088-1484: In layman terms, what is "engineering"?

RE: Quantity callouts

By the way, many folks religiously show center-lines in the type of pattern you're talking about - even if it leads to a messy drawing with lots of crossing center-lines etc.

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.

Posting guidelines FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm? (probably not aimed specifically at you)
What is Engineering anyway: FAQ1088-1484: In layman terms, what is "engineering"?

RE: Quantity callouts

I have never heard that centerlines "don't mean anything" and would tend to trust the actual standard more than interpretations that seem to defer from it.

"Know the rules well, so you can break them effectively."
-Dalai Lama XIV

RE: Quantity callouts

Quote (AMontembeault)

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"

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

Yes, I'll bet the point was that center lines don't imply any tolerance among the shared axes. But center lines do at least imply that the the axes are designed to be aligned.

John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems

RE: Quantity callouts

It would be helpful if they did clarify what to do for complex parts where the "inline" may not be as obvious.
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

I might argue that it would be more correct to use solid dimension extension lines rather than dashed center lines to indicate alignment between the hole centers as shown. A center line implies an axis of rotational symmetry, while a dimension extension line implies location of a surface or point relative to some other surface or point. And if extended implies location of a coincident surface or point along that extension line or curve. The use of center lines between the axes of hole features as shown does not define an axis of symmetry. The straight/parallel dimension extension lines shown imply that adjacent hole centers should be located in relation to those lines. Using center lines between the other hole axes would not necessarily imply they must be located along those straight lines. Just that the center lines must pass thru the axes of the holes, regardless of whatever shape they might take.

RE: Quantity callouts

tbuelna -- a center line doesn't necessarily imply an axis of rotational geometry. It could also be a center plane. See the attached snapshot from the Y14.5 standard, showing a planar block type of part.
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

I have to disagree with using a solid extension line through the center of a hole. The purpose of a centerline is to denote an item(s) center with a dash... to use a solid line defeats that purpose, and you may as well not use a centerline at all using that logic.

"Know the rules well, so you can break them effectively."
-Dalai Lama XIV

RE: Quantity callouts

Not only should the 'extension' lines between the holes be center lines, but also the extension lines outside the part to the actual dimension should also be center lines. This is consistently shown in Y14.5-2009 in, for example, Figures 1-6, 1-8, 1-14, 1-23, 1-32, 1-49, 1-50, et al.

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.

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources