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.

 

[Xplicator]

For those who don't have access to this standard. My copy is ANSI and dated 1979, the latest is ASME 1992. I can't imagine that the definition has changed but welcome any corrections if so.


[blue]ANSI Y14.2M-1979
3.5.1 Center lines. These are used to represent axes of symmetrical parts and features, bolt circles and paths of motion. See Figures 2 and 3. The long dashes of the center lines may very in length, depending upon the size of the drawing. Center lines should start and end with long dashes and should intersect by crossing the long or short dashes. Center lines should extend uniformly and distinctly a short distance beyond the object or feature of the drawing unless a longer extension is required for dimensioning or for some other purpose. they should not terminate at other lines of the drawing nor should they extend through the space between the views Very short center lines may be unbroken if no confusion results with other lines.[/blue]


The last sentence, in my opinion refers to the delineation of the center of a radial/cylindrical feature. This has been referred to here as the "center mark". The line convention used for center lines is thin. Thin line approximate width: 0.35mm/0.016" as opposed to the thick (visible line)which is approximately twice that of thin. These values are not for control of acceptance or cause for rejection of a drawing. They are for differentiation of line conventions.

This differentiation is witnessed when a hard copy of the spec is generated. Of course, compliant prints or plots are so rarely used correctly anymore that you don't necessarily see this. Most CAD packages do have this capability and others, but they are buried and unless this is something that you care about it is rarely set from the default correctly. There are those of you that do care, so I applaud you for employing this as a best practice, adhering to the standards as dictated.

In short the line convention of a center line is used to generate the termed "center mark" and it is a thin line.

Hope this post is beneficial.

 

[ringman]

I have made some searches in ASME standards and not yet found a definition for center marks. Anyone found a definition?.

 

[ewh]

I've looked thru what AMSE standards I have on hand as well as two industry acccepted DRMs based on ANSI/ASME, and I have found no mention of "center marks". I'm also curious as to where this term originated.

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

 

[KENAT]

Could it be a CAD thing?

They are called center mark on my current CAD system (the other Siemans offering).

Centerlines are a separate button/command.

So I propose it was a way to differentiate using CL to show the axis along the shaft and showing it in end view, if that makes sense.

What do ya reckon.

(Oops, bad Kenat checking Eng-Tips out side of approved breaks, better run.)

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

 

[fcsuper]

I learned about centermarks when I was in school learning on the manual drafting board.

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

 

[ringman]

What was the book that you used that provided a definition of Center Mark when you were learning on the drafting board?