Confusing/Odd looking datums 1

[KENAT]

Take a look at the attached sketch, it's a MUCH SIMPLIFIED & INCOMPLETE (so invoke 1.1.4 of ASME Y14.5M-1994 etc.) sketch of an actual case our contract checker came across on one of our parts today.

As far as we can tell looking at the standard B & D are valid, D is basically just used to locate the top radius centrally on the width of the item.

However, it just don't quite look right.

Anyone care to opine?


KENAT, probably the least qualified checker you'll ever meet...

 

[KENAT]

CheckerRon, I get that all the time, I'll show the 'plunger' in line with the dimension line on my redline and then the print comes back with it all over the place.

Especially frustrating when it's people that have supposedly had (or had access to) some level of GD&T training.

I'm not saying I'm going to use the "OK?" one but per the text of the standard I think it's possibly legit.

KENAT, probably the least qualified checker you'll ever meet...

 

[ctopher]

Per my earlier post.
A lot of people don't know what it means anyway.
I have had engineers, purchasing, machinists, checkers and inspectors come to me with a drawing and ask "What does this little triangle with a letter mean?".
With more designs going electronic, paperless, and pushed through quicker...people are not getting the sufficient training for GD&T.
So, IMO...follow Y14.5 to the best of your ability and hope the recipient can read and understand the drawing.

Chris
SolidWorks/PDMWorks 08 3.1
AutoCAD 06/08
ctopher's home (updated Jul 13, 2008)

 

[CheckerRon]

"What does this little triangle with a letter mean?"

You can blame ISO for that one.

 

[ctopher]

Chris
SolidWorks/PDMWorks 08 3.1
AutoCAD 06/08
ctopher's home (updated Jul 13, 2008)

 

[kanga147]

I believe that datums "C" & "D" are irrelevant. The position of the hole is covered by using basic dimensions from 2 edges a and positional tolerance.

 

[ewh]

D is used to control the position of R2.000.
C is required if you are going to use a vertical basic dimension to locate the hole (same as B & horizontal). If the dimension is basic, it has to connected to the related datum in some manner.
Therefore, datums C & D are NOT irrelevant. It just seems to be an unusual useage, thus the OP.

When the people fear their government, there is tyranny; when the government fears the people, there is liberty. - [small]Thomas Jefferson [/small]

 

[CheckerRon]

kanga147: I'm a bit surprised. As ewh just said, basic locating dimensions off datum surfaces is pretty basic stuff. How could C & D not be relavant?

 

[powerhound]

Yes, I too am curious as to why C and D are not relevant. I'll wait here with ewh and CheckerRon.

Powerhound, GDTP T-0419
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Inventor 2008
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[drawoh]

kanga147,

If you do not use datums[ ]C and/or[ ]D, you have a base and one edge as your reference. This is inadequate.

JHG

 

[KENAT]

Kanga, how much experience do you have with GD&T? Based on what I know I'd have to side with ewh, ron, powerhound & drawoh.

KENAT, probably the least qualified checker you'll ever meet...

 

[powerhound]

I hear crickets...

Powerhound, GDTP T-0419
Production Supervisor
Inventor 2008
Mastercam X2
Smartcam 11.1
SSG, U.S. Army
Taji, Iraq OIF II

 

[kanga147]

sorry I am mistaken, I stand corrected.