Specification of tolerances 1

[powerhound]

Hello all,
I'm having a minor debate about whether or not to specify ASME Y14.5M-1994 on a print or not. There are no GD&T symbols on the print, but I have a default note that specifies the standard on all prints because I apply GD&T every time I can. It scares our manufacturing department though so occasionally, I'll spare myself the headache of protest and leave the symbols off if the part isn't critical. Our manufacturing supervisor wants the note deleted on this one print in particular, probably because he feels like it will allow him more tolerance. My contention is that all prints should specify a standard to be checked by. If I leave the note out, does that means general rule #1 will not apply? Is it illegal not to specify a standard or is it just bad practice...or does it really even matter when there are no symbols?

Powerhound
Production Supervisor
Inventor 11
Mastercam X
Smartcam 11.1
SSG, U.S. Army
Taji, Iraq OIF II

 

[ewh]

Even if it contains no GD&T, it should state to which standard it is to be interpreted. ASME Y14.5 covers dimensioning and tolerancing in which GD&T does not have to be used.

 

[CheckerRon]

INDEED, It still relates to the first thiry pages of the standard that shows dimension practices and non-GDT tolerancing methods and interpretations.

 

[ctopher]

I agree.
IMO, people that do not want it on the dwgs, or used at all, are either lazy or ignorant.
I suggest having someone come in and give a demo on GD&T and setup some training.

Chris
Systems Analyst, I.S.
SolidWorks 06 4.1/PDMWorks 06
AutoCAD 06
ctopher's home (updated 10-27-06)

 

[powerhound]

ewh,
Thanks for the input. I understand that GD&T still applies even in the absence of symbols, but our manufacturing department doesn't. This is why I want to leave the note on the print if for no other reason than to maintain consistency. I'm afraid if I remove the note from this print, then they'll want it removed from all prints.

Powerhound
Production Supervisor
Inventor 11
Mastercam X
Smartcam 11.1
SSG, U.S. Army
Taji, Iraq OIF II

 

[ewh]

And once that happens, future drawings can be released no matter how poorly the parts are defined, and that will only cause more confusion. I don't know your full situation, but I would tend to stand my ground.

 

[dingy2]

Keep it on and make sure that it states "this drawing complies with ASME Y14.5M -94 rather than referencing the standard.

Dave D

 

[powerhound]

Well, it all started with an old print that the supervisor wanted re-drawn. It had a note that required a certain length of tubing to be straight enough to accept a rod along the entire length of the ID of the tube. The rod is exactly 1mm smaller than the ID of the tube so I added the callout of "straight within a diameter of 1mm" to the ID, using GD&T symbology of course, and eliminated the note. He flipped out accusing me of adding stuff to the print that wasn't there. When I tried to explain to him that it WAS there, albeit in antiquated terms, he went into total denial and wanted any reference to GD&T removed from the print.
So there you have it. On one hand, the print is pretty basic and it's probably not worth the fight for this print, but on the other hand, I don't want someone to get his foot in the door and start requesting all sorts of other stuff modified on a whim, just because he doesn't understand it.

Powerhound
Production Supervisor
Inventor 11
Mastercam X
Smartcam 11.1
SSG, U.S. Army
Taji, Iraq OIF II

 

[ctopher]

I had the same situation once.
I created a part dwg without and without GD&T. I asked purchasing to send them out separately for quotes. Then 2 weaks later send them out again, but swap the prints to each vendor.
I asked for the prices. Most of the parts that came back with the lesser $$ quotes had GD&T on the dwgs. (Of course not all of them did, but most).
Per ewh, stand your ground. I did and eventually won.

Chris
Systems Analyst, I.S.
SolidWorks 06 4.1/PDMWorks 06
AutoCAD 06
ctopher's home (updated 10-27-06)

 

[aardvarkdw]

The fact of the matter is that ASME Y14.5M-1994 is not a "GD&T" standard. It is a "Dimensioning" standard that defines how to use feature control frames and datums. If you don't specify a standard the drawing can be interpreted anyway the fab shop wants. ALLWAYS reference a standard if you intend to place dimensions on a drawing.

David

 

[powerhound]

My next question is this: Is there a standard that requires, or even recommends that a dimensioning standard be specified on a print? I know that will be the question when I approach our engineering manager with this.

Powerhound
Production Supervisor
Inventor 11
Mastercam X
Smartcam 11.1
SSG, U.S. Army
Taji, Iraq OIF II

 

[aardvarkdw]

No, unless your company has it as part of it's own internal drafting practices and standards. However, if you don't have a document telling someone how to interpret your drawing, there is no way for you to guarentee that your fab shop is building to match the drawing. Specifying a standard is the only way that you can ensure that your drawing is interpreted properly. Not spec'ing and standard is like sending someone a coded message but not telling them how to decode it, they may get it right the first time, on the other hand they may not, chances are good they will get most of it but what about the really important parts?

 

[KENAT]

Just to support what pretty much everyone else has already said.

There is a lot of other stuff in Y14.5 other than GD&T so just because you don't have any feature control frames etc doesn't mean 14.5 doesn't apply.

Also as Aardvarkdw says you should really say to what standard your drawing is to allow interpretation.

Firstly because there are differences between the various international standards.

Secondly because if you don't specify any standard then you'd have to add hordes of notes about things like 'edges drawn at 90 degrees are assumed to be 90 within general drawing tol' etc and all the other 'standard conventions' we take as read, even so far as probably defining what angle of projection is used and what it means etc for it to be 'unambiguous'.

This doesn't just go for 14.5. For instance while not compulsory and not apparently standard practice the asme thread standard does recommend that it be referenced on drawings calling out threads.

In my opinion, and training, if you’re using a standard to help define something you should reference that standard (directly or sometimes indirectly as applicable), even if it seems obvious to you.

 

[MechNorth]

Another point to raise in your argument with the boss is that without datums, you aren't specifying how to verify the part. Even a simple part needs to be verified in some way, and we all know that setup (orientation) is important. Without putting FCFs all over the place, you can still specify a general setup; e.g. VERIFICATION PER DATUM SEQUENCE X/A/J. To do that, you need to specify a standard to which it conforms.

Jim Sykes, P.Eng, GDTP-S
Profile Services
CAD-Documentation-GD&T-Product Development

http://www.profileservices.ca

 

[jakfishjak]

Can you perhaps put the drawing back the way it was without the gd&t, clean up the print, leave in the standard and move on to the next thing? Do you think he would sign it then? It seams like he might be intimidated by the gdt on the face of the drawing.