ASME Y14.100-2000 versus ASME Y14.5M-1994 and ANSI 1982

[cadtemp2]

Is PTC going to add optional toggles for wearing the appropriate hat for this newest GD&T spec?



I just became aware of this newest drafting spec.

Actually the company I contract at presently (mis-)uses an approach to only the ANSI Y14.5M-1982 standard. Their twist is to NOT use any positional tolerance callouts as they have had too much mis-intrepretings from it's initial use.



I am loading some manual drawings from 1947-1965 era, into Pro/E as models and drawings. Therefore, we are considering using the newest spec that our vendors can read and work to. I am going to now investigate what significant changes were incorporated in this 2000 standard - and I just got used to the 1994 standard! Sort of like Pro/E, and Windchill.

Old dogs learning new tricks...

 

[Tunalover]

Take a look at the available configuration settings (e.g. for config.sup, config.pro, and/or *.dtl files). I believe there is a way to change the GD&T convention from 1982 to 1994 and vice versa. I don't think that there is a toggle to accomplish this.

Tunalover

 

[Tunalover]

You do understand that Y14.100 is NOT a dimensioning and tolerancing standard? It is a general drafting standard. Be advised that it probably INVOKES Y14.5M-1994, but it doesn't replace it.



As far as I know, ASME 14.5M-1994 is still the defacto dimensioning and tolerancing standard. If something has changed, then please let all of us know!



Tunalover

 

[cadtemp2]

My mistake. Indeed ASME Y14.5M-1994 is the current standard. I feel silly for not doing my homework before asking the question. The lead designer for the department took me to task after I corrected their older drawings for errantly defined feature control symbols. He said If you want use to use the newest standard then teach use this 2000 spec (i.e Y14.100-2000) not the out-of-date Y14.5M-1994 standard, and he caught me off guard. It is a BIG book too!



They are inclined to continue using the ANSI Y14.5M-1982 spec on the few drawings that do callout GD&T even to its limited use without changing any conventions. They are afraid that changes to drawings might give the opportunity to have vendors re-quote prices for the same parts because the drawing now calls out GD&T. Many of these parts have been manufactured, delivered, inspected, and used based on these non-GD&T drawings for decades, and they don't want to mess it up now. As tight of tolerances that these designs require - optics design - I wonder how it could have been done RIGHT all these years without consistent datum references.

 

[cadtemp2]

I should have said in my attempted humorous analogy...

Sort of like Pro/E and Wildfire. Old dogs learning new tricks.

 

[Tunalover]

I've found that 100% of fab vendors SAY they understand Y14.5 while 15% DO understand Y14.5. The latter give reasonable pricing. The former normally react as follows:



1. They guy sees a feature control frame and promptly chastises the designer (in absentia) for overkill. This is normally done in front of the machinists who don't understand the method either but they just like to bond this way. Of course, none of them understand that the tolerance is probably looser than the bilateral tolerances they're used to but that really doesn't matter to them because of their ignorance.

2. The vendor then tacks on 40%-75% to cover the obsessive, time-consuming behavior taken by the machinist to hit the feature dead nuts. The machinists do this whenever they see the funny symbols. After all, the fancy symbols mean tight tolerances, don't they?



I've been carrying the torch with GD&T since 1984 and the ignorance by so many of such a superior method never ceases to amaze me!



Tunalover