Positional Tolerance

[asmeY145Manswer]

The positional tolerance of this hole can never be gauged. There is no reference to any datums, and secondly, there are no basic dimensions, which would give me a theoretical true position for the axis of that hole. And consequently, I cannot calculate a bonus tolerance, because I dont know how much the tolerance of size is allowed to vary from its Maximum Material Condition (MMC). The guage you are proposing will only measure tolerance of size. And the question you must ask then is, do you want that guage to measure the LMC or MMC of the hole, and do you want it to be a Go, or NOGO guage. There are plus guages, and minus guages, that do just that. You have to determine which one should be go/nogo. And that depends on whether you are controlling an ID or and OD. So you figure that much out! But then, you will only be guaging tolerance of size. You cannot guage a positional tolerance here for the reasons given above.

So I suggest that You, as the Guage Design Engineer, refer this back to your Special Design Group (SDG), or whatever they call themselves, and recommend a design change. And I would further suggest, that you suggest, that SDG, be thoroughly familiar with ASME Y14.5M 2009, and be certified, before they send drawings like this to manufacturing.

And I am pretty sure that you are probably working for a worthless medical device company that does stuff like this all the time. Right?

 

[fsincox]

Looks like we are missing alot of information here!

 

[asmeY145Manswer]

Sorry, fsincox,

This was a drawing I found on another post. I meant to reply to the post but it didn't let me for some reason. I will find out who sent it so you can see the thread.

Here is the drawing. I have seen too many drawings like this in my time. And then have to listen to crap like - oh SDG can't change this drawing. Our special design process is far too regulated. We have to comply with 510K medical device requirements! And this has already been approved. So now live with it! But make it work, and we don't care how you do it!

That is the reality now in lots of medical device companies in our brave new world!

Should make anyone shudder, next time you go to see your doctor!

But beyond any of that, I cannot elaborate!

 

[fsincox]

I too see lots of this in aerospace and feel the same way!
Frank