What has priority, notes or title block?

[James7443]

I have a number of drawings that have a note that states the tolerance is +/-.010, +/-.025, etc.. The standard title block on all the drawings have a hard written tolerance block with +/-.005. This is not a variable field, just +/-.005 on all formats.

I now have one vendor that is questioning it. I don't want to manually update the format on individual drawings out of fear that someday down the road someone will change the format to a different size or when there is a new company logo and then the tolerance would change back to the standard title block tolerance. I suppose I could change the title block tolerance to a variable but then there is a chance that other may forget to set the variable on new drawings.

I have looked thru the ASME specs but haven't found anything that states that notes take precedence over the title block. Does anyone know if there is anything called out stating what has precedence? How is everyone else handling this situation?

Thanks,

Ron

 

[3DDave]

Neither has precedence. All elements of a drawing are coordinated, and if there is a mismatch then it needs to be repaired.

Normally only a title block general tolerance will be on the drawing, with a note that it applies unless otherwise specified. Then individual dimensions will have individual exceptional tolerances applied.

If the format is badly formed and does not include exception handling, then overriding it is accomplished by crossing it out. One should be able to use a note 'ignore format tolerance and use this ...' but crossing out it much more obvious.

As to the last part, about being variable, some companies do not allow any general tolerances and require each dimension to have one, either directly applied or via Feature Control Frame. TACOM, for example, specifically prohibits title-block tolerances on angles. An incomplete drawing is incomplete, no matter what it is that is overlooked.

 

[MintJulep]

Just about every drawing title block tolerance box has "Unless otherwise specified" or "Unless otherwise noted" right there at the top.

But why don't you change the numbers in the title block rather than adding a note?

 

[James7443]

Thank you both for your responses.

Let me explain a little more. These are legacy drawings, that I have inherited, that have these general notes added. Although they are in CAD format now, their origins may have started in the days of drafting tables with velum and pencil. In those days, and I am dating myself, the format was printed on the velum (paper)by an outside printer. If you wanted to change something in the format you either had to use an electric eraser and grind away at the format or line it out and note it somewhere else. The electric eraser method sometimes didn't leave the drawing very pretty looking.

Before I go through the process of updating all of these documents I thought I would ask if there are any drawing standards the indicate I can leave the notes as is. I would think anyone reading the drawing that has a title block calling +/-.005 and a note calling for +/-.010, would use the +/-.010 since it is called out. It should be noted that the title block does have the "Unless otherwise specified" line.

If anyone else has comments I would be glad to hear them.

I think I know what I am going to do, but I just don't want to create more work for myself if I don't have too.

Ron

 

[pmarc]

So if there is the "Unless otherwise specified" line in the title block, the tolerance from the note overrides the one from the title block.

 

[James7443]

True. I the drawing that this vendor is currently questioning, the title block has +/-.005 and "unless otherwise specified", the note calls out xxx=+/-.010, and three dimensions on the drawing have +/-.015. The other 12 or so dimensions do not call out any tolerance modification.

I should also state that I have found some drawings that have "unless otherwise specified" in both the title block and the note. I don't believe this particular vendor has seen these prints.

To be thorough and cover all of my bases I wanted to post this message and gather as much information as available, and determine if there is any specification that states notes supersede or have priority of general title block information. As I am sure the vendor will continue to question it, I will need to address this subject within my company. For the most part I don't anticipate any problems internally with changing the method of tolerance callouts, but then again I have seen big resistance at times to the simplest of changes.

Ron

 

[Belanger]

Even though the "unless otherwise specified" clause does give an answer to the question (the other note is "otherwise specified"), it's still a bad practice in my thinking, simply because of the potential for confusion.
We should be not be making prints that can merely be understood, but we should be making prints that cannot be misunderstood.

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

 

[James7443]

John-Paul,

I completely agree. My current plan is to update all of the drawing formats to have the tolerance field in the title block be a variable that need to added on each drawing. That way if the drawing has the format updated in the future for size, company logo, etc.. the tolerance will not get modified.

I just need to completely research the subject and have evidence as to why I want to change potentially hundreds of drawings.

Ron

 

[powerhound]

I'm with those who say the prints have to be fixed. The prints that have "UNLESS OTHERWISE SPECIFIED" in both areas are especially bad. You should just bite the bullet and get started right away. If you've been getting working parts in spite of the bad prints, it's probably on account of tribal knowledge already communicated in the past to the vendors.

John Acosta, GDTP S-0731
Engineering Technician
Inventor 2013
Mastercam X6
Smartcam 11.1
SSG, U.S. Army
Taji, Iraq OIF II

 

[Tunalover]

John Acosta-
I thought we pulled out of Iraq. Are you still there?


Tunalover

 

[CheckerHater]

Ron,

Even if you cannot change tolerance section of your title block for some reason, you can always draw the line or two to cross it out.

This will remove the confusion for the time until you put all of your drawings/tile blocks in order.

 

[TheTick]

Since the revised tolerance is in the notes, would it be too much trouble to also note that this supersedes the TB tolerance?

I've always held that notes supersede TB, and that specific dimension tolerances supersede notes. I'll bet that most standards have chapter-and-verse for this, but I don't know. Then again, the drawing in question is likely not compliant with a specific standard anyhow.

When in doubt, make a phone call.

 

[HGMorgan]

There is no need to change anything.
Title block tol is already noted "Unless otherwise specified".
So, if title block says .xxx = +/-.010, then all .xxx dim's on the drawing have a tol of +/-.010, UNLESS OTHERWISE SPECIFIED.
A dim of 10.000 +/-.005, or 20.000(NOTE3): is otherwise specified with the tol that applies to that dim only.
This was done to simplify the drawing and remove the need to put a tol on each and every dim.
The Title Block tol, specific dim tol, and note tol are not in conflict with each other, they support each other.
This format is on hundreds of thousands of drawings (if not millions), it a standard for all the major aerospace companies I have worked for, it is still in use today, and most importantly, it just makes sense. We would not spend the time and money to go "fix" this, because it ain't broke.




Harold G. Morgan
CATIA, QA, CNC & CMM Programmer

 

[Belanger]

But if I understand it, the original question involved two general tolerances -- not even considering a specific tolerance applied to a specific dimension on the field of the drawing.
The two were: one within the company standard title block (which would have the caveat "unless otherwise specified") but then another verbal note on the drawing giving different default ± tolerances.
Am I reading the question right?

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

 

[HGMorgan]

I think it might be best if we were given a view of the items in question, however, I still don't see what difference it would make:
"unless otherwise specified" has been "otherwise specified" by a note on the drawing...
I'm not trying to start a fire debate: I just have seen this for many decades, and I think it make sense.
Design Engineer wants all dim tol's per Title Block: done with that aspect of drawing.
Design Engineer wants dim tol's different than Title Block: specify. A note is a specification.

Harold G. Morgan
CATIA, QA, CNC & CMM Programmer

 

[James7443]

We have had a lot of good comments on this subject. I think the majority of my drawings are OK since there is the "Unless otherwise specified" in the format title block. Not saying this is the best way, just it is what it is. There are some that throw a little more verbiage that may cause a problem.

Remember what I am looking for is if there is a paragraph or sentence hidden somewhere in the ASME Y14 series that says if there is a conflict, then one take precedence over the other. I have browsed through the ASME Y14 series and didn't find anything but them I didn't read the entire set. I know that I have see documents before, for purchase orders, that state PO have priority over drawings when there is a conflict, although that might just be a purchasing thing that most companies do.

The only reason for asking is so I can prioritize this as a low level project if there is a spec that covers this subject. I can then work on more important projects and correct these print one at a time as they arise.

Ron

 

[dgallup]

We have an engineering standard that explicitly states all our drawing practices. Since we use ISO & ISO is a jumble of sometimes conflicting standards it's a very useful and necessary document. One of the things it has is an order of precedence in case of conflicts. It does not cover your situation where there might be conflicts within the drawing itself but it's a place where something like that could be addressed. However, it would be better to clear up your drawings directly rather than rely on another document that may not be available when needed on the shop floor or at a supplier.

----------------------------------------

The Help for this program was created in Windows Help format, which depends on a feature that isn't included in this version of Windows.

 

[JNieman]

I've had this mental hierarchy that may have simply been an industry-taught thing. However, I'm curious if there /is/ a standard to "order of precedence".

I have this mental flow chart in mind that goes (dimension tolerance) > (view notes) > (sheet notes) > (general notes for entire tool/part/assembly) > (title block text)

And that's been true every time so far in my career. The times we /do/ ask for clarification, such as a general note for the drawing package conflicting with a separate document in the package, it's had a consistent response, from various customers.

Is this any standard by ASME or any else?

_________________________________________
NX8.0, Solidworks 2014, AutoCAD, Enovia V5

 

[3DDave]

"Remember what I am looking for is if there is a paragraph or sentence hidden somewhere in the ASME Y14 series that says if there is a conflict, then one take precedence over the other."

It seems as if you have a lot of reading to do to locate text that would certainly stick in the minds of those who have read 14.100 and 14.5 and others, but that no one here can recall.

Adding a note to the P.O.s to clarify what should be done with this particular drawing error would save fixing the drawings.

 

[HGMorgan]

OK, here is my last shot at this...(do I hear applause?) There isn't any conflict. There isn't anything in the ASME Y14 series specically about this.
Here is an example from one of the largest aerospace companies in the world. The following tolerances are in the General Notes (Excel File) of a Tool Design.
"Tolerances as shown:
X=+/-.1______XX=+/-.03______XXX=+/-.010______XXXX=+/-.0050
Angular Tolerance = 1/2 degree x 10 in. unless otherwise noted in the 3D dataset.
Tolerances per ASME-Y14.41-2003, Dimensions are in inches and views in third angle projection-USA.
~ Material Stock Size is Net in Bill of Material, unless otherwise noted."
These tolerances are General Notes tolerances (used to be Title Block tolerances). Notice that they don't even say "unless otherwise specified".
These tolerances are for any dimension that doesn't have a specific tolerance called out.
This Tool Design has several sheets.
On Sheet 7, there some dim's as follows: 3.13 MAX & 1.13 +.03/-.00 (if the note or tol wasn't there, these dim's would have +/-.03 tol per GN)
On Sheet 8, there is a close tolerance pin dia: .250 +.0000/-.0002 (if the tol wasn't there, this dim would have +/-.010 tol per GN)

Harold G. Morgan
CATIA, QA, CNC & CMM Programmer