Center marks where feature is dimensioned 3

[lmdrafting]

An engineer is challenging me on what I have always considered basic dimensioning rules. He puts center marks on every single hole in every view. I typically only place center marks in views where the feature is dimensioned. The engineer wants me to give him an ASME requirement that mandates this or he won't change it. Is there such a thing? Ahh the joys of being a checker.

 

[powerhound]

Ask him to show you a requirement that mandates the application of centerlines on every single hole in every view. He won't find it. In my opinion, centerlines should only be used where the dimensioning would not be clear otherwise, or to invoke the fundamentals rules regarding implied 90's, but there are others here within this forum that cut their teeth on showing every centerline on every cylindrical feature regardless of whether they are useful or not.
If you are the checker, then it seems that you would be the authority and the burden of proof would be on the engineer to prove his case to you.

Powerhound, GDTP T-0419
Production Supervisor
Inventor 2008
Mastercam X2
Smartcam 11.1
SSG, U.S. Army
Taji, Iraq OIF II

 

[ringman]

They say there are no dumb questions. But, what is a 'center mark'?

 

[lmdrafting]

I could be using the incorrect terminology. I'm defining center mark as the center of a hole.

 

[lmdrafting]

Thx powerhound for your input. I'll have to try that approach

 

[fcsuper]

The ASME standards are a set of rules that are to be followed. Anything not in the standard is not a requirement.

Matt Lorono
CAD Engineer/ECN Analyst
Silicon Valley, CA
Lorono's SolidWorks Resources
Co-moderator of Solidworks Yahoo! Group
and Mechnical.Engineering Yahoo! Group

 

[Xplicator]

This is not necessarily a dimension rule but an Engineering Drawing Requirement. My interpretation is fueled by ASME Y14.24, 3 DETAIL DRAWING. 3.1.3 Requirements - A monodetail drawing delineates all features of the part...

DELINEATE - de•lin•eate
1 a: to indicate or represent by drawn or painted lines b: to mark the outline of
2: to describe, portray, or set forth with accuracy or in detail
(Merriam-Webster's online)

You can look next to line conventions in ASME Y14.2M, 3.5.1 Center Lines - "These are used to represent axes of symmetrical parts and features..."

This in my opinion indicates the use of centerlines on the cylindrical/radial features of a part. Not to mention nearly all figures in the Y14 standards use this same approach to depict there examples. By the way center marks are center lines that intersect @ 90°.

I would also like to add that there is of course more direction when applying dimensions and tolerances in ASME Y14.5M.

Additionally, I realize that there is the ASME Y14.100, Engineering Drawing Practices. Now this may say something different however my copy seems to have grown legs, so I cannot cite it at this time. Perhaps others can provide what is stated by this standard to support or disprove what I am saying.

The only place I find where one of the standards actually states to omit the center line/center mark is for example when a scenario such as a tangent to tangent relationship is required and the location is unimportant. (ASME Y14.5M, 1.8.2.1)

I guess my final thoughts are more questions - is an axis not an attribute or characteristic of all cylindrical/radial features? Does it not locate the feature? The graphical representation of this attribute in an engineering drawing communicates complete unambiguous representation of the feature?

This all of course is just my opinion and my practice, so take what you can use and discard the rest.

Last but not least I ask not why, but why not include this on your drawings? Does it not make your drawing more complete and in the end, at what real effort?

 

[ctopher]

Cneter-lines or center-marks only add clutter to a dwg. Sometimes they are needed to clarify where the dim is pinting to. Other than using dims, leave them off.

Chris
SolidWorks/PDMWorks 08 3.1
AutoCAD 06/08
ctopher's home (updated 10-07-07)

 

[ewh]

I cut my "teeth on showing every centerline on every cylindrical feature regardless of whether they are useful or not." When my drawings started to get too cluttered, I balked, and won.
For simpler parts this is not really an issue. For complex parts with many such features, it only crowds and confuses the drawing. Of course they should always be present where the feature is being dimensioned. There should also be some present in other views to aid in part visualization. To carry it to the extreme and mandate that ALL such centerlines be shown is folly. For example, a round plate with a hole pattern of 50 holes should not have every centerline shown in a side view. If the part is crowded with other features, carrying those centerlines into other views will only confuse the intent of those views. It can get to the point where they will obscure any other information the view is trying to present.
I don't have a standard at hand which directly addresses this issue to verify which is the correct practice, but common sense tells me that it is silly to insist on every such feature having a centerline every place that feature is shown, unless it is being referred to directly.

"ASME Y14.24, 3 DETAIL DRAWING. 3.1.3 Requirements - A monodetail drawing delineates all features of the part..."
Filling up a drawing with clutter that only confuses the purpose is not a requirement of the standard. The examples provided in the standard show many occurances of holes without any centerlines if those holes are not being referred to in the view. The standard examples are also a poor guide to follow for anything other than which the examples are addressing.


Believe it if you need it or leave it if you dare. - [small]Robert Hunter[/small]

 

[fcsuper]

The spirit of ASME Y14.100 is to provide clear and meaningful specifications. It seems to me that in holding to that spirit, centermarks are required where they are used to delineate. Otherwise, of what good are they? They potentially reduce clarity on the drawing by creating clutter. As stated, not a big deal for simple drawings, but a very big deal for complex ones.

Does this mean to only use them when there is a dimension to them? No. Does this mean to use them in every hole on every view regardless of delineation? Also no.

In my case, I used centermarks where they provide additional information in conjunction with an actual specification. This helps identify them, even if I don't have dimensions to each one specifically. However, in massive patterns, I will only use centermarks on the initial feature of the pattern.

Matt Lorono
CAD Engineer/ECN Analyst
Silicon Valley, CA
Lorono's SolidWorks Resources
Co-moderator of Solidworks Yahoo! Group
and Mechnical.Engineering Yahoo! Group

 

[Xplicator]

Of course common sense must prevail. The range of drawings from simple to complex does exist although the majority fall somewhere in between. I have had on occasion found that some drawings got to "busy" thus I added a note that simply states

SOME HIDDEN LINES AND CENTER LINES HAVE BEEN OMITTED FOR CLARITY.

This method has been well received by vendors/suppliers, not so much by those having to make a few extra mouse clicks.

Again this is my suggested best practice, I would start with use of all line conventions where applicable and hide/delete them whenever clutter and clarity becomes an issue to the intended "audience", then add this simple note.

The level of clutter is deemed by the specifiers perspective. This of course is a gray area because the quality of an object is found only in the eye of the beholder. So my level of clutter or clarity might not be someone else's level and vice-versa.

So having said this, it is really up to you and your organization to determine what works best for you and the intended "audience". I just know what I have done and will continue to suggest in hopes of achieving drawings with the level of details that qualify them as drawings of high quality and workmanship.

Hope this was helpful.

 

[lmdrafting]

This has been very helpful. Thank you all for your input. And yes, I agree...the ultimate goal in the end is consistent, high quality drawings.

Thanks again!

 

[KENAT]

Well I think others summarized my view, including the last post from Ithurner.

If it adds clarity/makes the drawings easier to understand or is explicitly required then put the CL/Centermark.

If not, and it's only adding clutter, leave it off.

KENAT, probably the least qualified checker you'll ever meet...

 

[ewh]

... and unless he started as a drafter, don't rely on an engineer for drafting advice. Even then, documented standards are invaluable.

Believe it if you need it or leave it if you dare. - [small]Robert Hunter[/small]

 

[KENAT]

ewh, you just hit one of my limitations. I'm going to go off and pout now!

However, it's a good point that my current employer constantly proves.

KENAT, probably the least qualified checker you'll ever meet...

 

[ewh]

KENAT,
You are an exception which proves the rule. The vast majority of engineers that I have worked with never consider the finer points of a well done drawing (and wouldn't recognize one if they saw it), as long as the info is there. They never had to bother with correcting "silly" mistakes time and time again.
You are a vanishing breed, since most drawings are only checked by co-workers anymore. The dreaded checker with all of the colored pencils is only a myth to most of the younger engineers today. You are appreciated.

Believe it if you need it or leave it if you dare. - [small]Robert Hunter[/small]

 

[pierdesign]

from ewh post above regarding centermarks:Of course they should always be present where the feature is being dimensioned.

Is this true of ASME / ISO, etc., or just personal style?

 

[ewh]

It is less personal style than it is a lesson learned (from drawings repeatedly bled on for one omission or another). There are situations where dimensioning to the hole and omitting the centerline can be ambigious, such as reduced scale drawings. Per ASME Y14.2 "Center lines are used to represent the center of holes...", thus when dimensioning to the center of a hole, a centerline should be used. I admit that this is my interpretation of the standard, but it is not "only" my interpretation, as EVERYWHERE I have worked to create engineering drawings followed this practice. Of course, some industries do not follow these standards, and I cannot address those.

Believe it if you need it or leave it if you dare. - [small]Robert Hunter[/small]

 

[ringman]

Does 'center mark' imply 'centerline'?

Or is is just a small x to indicate the center of a radius?

 

[ewh]

I implied center mark to mean centerline. The OP may have a different meaning.
To expound on my previous post, I have often seen circles dimensioned to tangencies, so dimensioning to a circle without a centerline leaves ambiguity, especially on small circles. Granted, this is just my rationalization, but judicious use of centerlines can be an aid to the ease of reading a drawing.

Believe it if you need it or leave it if you dare. - [small]Robert Hunter[/small]