A reference dimension is a dimension that is non-critical to the making of the part. As an example; Very often a casting may shrink and somebody did not calculate the shrink factor correctly. Perhaps we wanted it to be 8 inches and it comes out somewhat smaller. Still, the part is machined...
That is a very good point, Frank. I forgot to mention that.
I have such a bad time getting my students to look down into the title block for general notes and tolerances.
One could say that a basic dimension is a dimension to override any general tolerances.
This is a good point I will have...
Hey ewh, we were all punks at one time.
I would just encourage you to look into the use of basic dimensions more.
The most important thing, to me, is that you not get into it some day with some guy that can make your life miserable.
I once had an old soul lecture me about drawing asking me if...
KENAT,
I am sorry.
However, if you go back through this blog and look at all the posts, I think I was not the one to take us down this road of disrespect.
I have a passion for what I do and a passion for doing things correctly. I am sorry if this offended anybody here.
I had a very strict...
Not as bad as you Powerhound. I have been in this since 1975 and my professor was on the ANSI board. He helped Caterpillar go metric and go GD&T.
Try again.
As my good ole professor used to say, "There are a lot of bad GD&T drawings out there done by people who think they know what they are...
Dean,
How do you think they inspect parts in industry?
The example of the wheel hub and studs with two similar but different wheels is a great way to understand basic dimensions and positional tolerancing.
The studs, center marks of the holes located by basic dimensions, are assumed to be...
Well, you are a smart ass who thinks he knows it all so I will admit I was wrong in trying to offer your something to keep you from making an ass out of yourself one day.
It is pretty plain to me you have yet to work in the field.
The drawing submitted with every dimension made basic is in...
That must be why I have the 2009 standards and have pitched the other two you alude to.
I will try to figure out if those figures you mention are still in there and what you are talking about.
All I am trying to do here is have a teaching moment where you do not go out of here and get railed...
Okay... I tried to educate some people here who pretty much think they know it all but show they have yet to truly see the world.
Many times have I gotten my butt chewed by my elders for coming off as you are to me now.
You think you know it all but you do not. Offer some proof rather than...
"You clearly have your own set of standards that are independent of any established and documented national standards."
Find me one drawing in a text or ASME manual dimensioned like the one that began this blog. You won't! It is done wrong.
"Unneeded basic dimensions should be deleted from a...
So when you buy something like 1 inch round bar stock, you do not expect it to be 1 inch?
I have trouble getting this through to my students all the time...
I use two other examples to help them understand... one is mechanical and the other architectural:
When you go to the hardware store to...
Okay, I am not sure what the example Tec-Ease has to do with this...
Basic dimensions in the problem of this post should only be used off of the flange edges that would have presumably been ground flat to locate the patterns of holes in true position.
My point is you do not just randomly throw...
While I admire your service to our country as well as your title, I stand by what I have stated and you are wrong.
I hold two degrees and was taught GD&T by one of its masters who also taught it to Caterpillar Tractor.
If you are making basic dimensions off of surfaces that are truly reference...
True, but it is typically used for position and surely not used as is done in this drawing. It would be impossible to make this part.
In the first place, the part is a casting of unfinished edges. In the second place BASIC implies theoretically perfect, such as stock materials.
Making every...
You only use Basic dimensions for positional tolerancing. Because this is a cast part, you could not basic off of the edges of it. Your idea of datum selection is solid but you would really need to know the application of the part before picking them. One of the 4 holes in the base could have...
