Center marks where feature is dimensioned
Center marks where feature is dimensioned
(OP)
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.





RE: Center marks where feature is dimensioned
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.
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RE: Center marks where feature is dimensioned
RE: Center marks where feature is dimensioned
RE: Center marks where feature is dimensioned
RE: Center marks where feature is dimensioned
Matt Lorono
CAD Engineer/ECN Analyst
Silicon Valley, CA
Lorono's SolidWorks Resources
Co-moderator of Solidworks Yahoo! Group
and Mechnical.Engineering Yahoo! Group
RE: Center marks where feature is dimensioned
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?
RE: Center marks where feature is dimensioned
Chris
SolidWorks/PDMWorks 08 3.1
AutoCAD 06/08
ctopher's home (updated 10-07-07)
RE: Center marks where feature is dimensioned
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. - Robert Hunter
RE: Center marks where feature is dimensioned
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
RE: Center marks where feature is dimensioned
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.
RE: Center marks where feature is dimensioned
Thanks again!
RE: Center marks where feature is dimensioned
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...
RE: Center marks where feature is dimensioned
Believe it if you need it or leave it if you dare. - Robert Hunter
RE: Center marks where feature is dimensioned
However, it's a good point that my current employer constantly proves.
KENAT, probably the least qualified checker you'll ever meet...
RE: Center marks where feature is dimensioned
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. - Robert Hunter
RE: Center marks where feature is dimensioned
Is this true of ASME / ISO, etc., or just personal style?
RE: Center marks where feature is dimensioned
Believe it if you need it or leave it if you dare. - Robert Hunter
RE: Center marks where feature is dimensioned
Or is is just a small x to indicate the center of a radius?
RE: Center marks where feature is dimensioned
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. - Robert Hunter
RE: Center marks where feature is dimensioned
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.
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.
RE: Center marks where feature is dimensioned
RE: Center marks where feature is dimensioned
Believe it if you need it or leave it if you dare. - Robert Hunter
RE: Center marks where feature is dimensioned
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...
RE: Center marks where feature is dimensioned
Matt Lorono
CAD Engineer/ECN Analyst
Silicon Valley, CA
Lorono's SolidWorks Resources
Co-moderator of Solidworks Yahoo! Group
and Mechnical.Engineering Yahoo! Group
RE: Center marks where feature is dimensioned