Help Interpreting Drawing

[Chaldaean]

I'm looking for an explanation of the feature control frame outlined in red within the attached.

I'll take a stab at the meaning: The position of the axis of the shaft (along the entire length of the shaft) must be within a 1.1 diameter circle after the part is first fixtured relative to datum A and then to datum B.

Is this accurate?

Also, what does the "L" (least material condition) mean as applied to datum B? Does that mean when the inspection fixture is produced, the fixture should be at max material condition (4.52 as drawn)?

Thanks for taking the time!

 

[pmarc]

J-P,
Answering shortly to your question, I would say that for clarity such note should be put somewhere on a print.

I know your previous response was directly based on the letter of Y14.5, however in my opinion the standard itself was ('94)/is ('09) not clear enough on this topic and this is why I said there was something not OK with this.

Let me just cite how the newest edition of ISO 8015, dated 2011, is dealing with the subject: "By default, a workpiece shall be considered as having infinite stiffness and all GPS specifications apply in the free state, undeformed by any external forces including the force of gravity. Any additional or other conditions that apply to the workpiece shall be defined in the drawing." Doesn't this sound much more reasonable?

Let's imagine for a moment that OP's print is according to ISO GD&T. If the shaft/needle was subjected to a form variation in free-state condition, the print would have to say that. Since there is no info about such variation, the feature would have to be assumed infinitely stiff. Now, if this was ASME's rule too, there would be no other choice than unanimous conclusion that for this particular print Rule #1 applies to the shaft and that the straighness callout is illegal.

Apologies if I formulated my thoughts not clear enough.

 

[Belanger]

Certainly, the position of 8015 is much more clear, I agree.

If the OP's print is ISO, then we'd assume a rigid part. However, that's irrelevant to the idea of "perfect form" since ISO does not observe the envelope principle / Rule #1. (I know you know that, but I'm just musing as I type ... if there's no Rule #1, who cares if it's rigid or non-rigid to begin with?)

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

http://www.gdtseminars.com

 

[fcsuper]

Belanger,

ISO does have a couple of conceptional "differences" ::cough::issues::cough:: They do have have rule one when circled E is applied. Also, up until very recently, the BSI varient of ISO did apply Rule 1 by default, but now uses the Delta D to signify when a drawing is using Rule 1.

Matt Lorono, CSWP
Product Definition Specialist, DS SolidWorks Corp
Personal sites:
Lorono's SolidWorks Resources & SolidWorks Legion

 

[powerhound]

Delta D, not to be confused with the indicator of what changed on drawing revision D.

Powerhound, GDTP T-0419
Engineering Technician
Inventor 2010
Mastercam X5
Smartcam 11.1
SSG, U.S. Army
Taji, Iraq OIF II

 

[fsincox]

I actually suspect it is just this kind of issue the ISO is tackling by forcing an engineer to "state it if they want it" so to speak, don't just assume that it will happen. It is tougher on us, but I respect the intent and feel it is our job in the end.
I think it is issues like this that show the standards have been too oriented to describing machined solid parts, just like it seems to be too focused on using gages to check things. I understand it is helpful to explain concepts but some seem to think it is the only way to check parts, "because the book shows it that way", how do we little short run shops, ever get by without them? Or should we all just close up shop?
Frank