Help determining proper symbol
Help determining proper symbol
(OP)
We are having a bit of trouble with a valve housing coming in from an outsourse machine shop. As you can see, I have the 9.000 diameter circled. This is our trouble area. What is happening is that the valve is measuring 9.002 in the "north/south" direction. However, in the east/west direction we get a measurment of 8.998. We would like to add a control frame to this dimension to help hold it's circularity. What would be the most appropriate symbol?
Thanks,
Pal
Thanks,
Pal





RE: Help determining proper symbol
"Good to know you got shoes to wear when you find the floor." - Robert Hunter
RE: Help determining proper symbol
As ewh says the control you want is probably circularity. The symbol for this in a Feature Control Frame is a circle.
What standard are your drawings to? Looks like an older version of ANSI/ASME Y14.5 but I didn't see it stated. I don't think this makes a difference but can't be sure as I've only worked the 94 version. Section 6.4.3 in the 94 standard explains its use.
KENAT,
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RE: Help determining proper symbol
So your measured value of 9.002 is outside the existing tolerance anyway, isn't it?
Just adding a control wont necessarily fix things if the manufacturing process fundamentally can't meet the tolerance regardless of how it's specified.
KENAT,
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RE: Help determining proper symbol
But if do wish to control it more, yes circularity should do it. Phrased from the book - "A form tolerance is considered when the size tolerance (only) of the concerned feature does not adequately provide the needed control"
Are you sending this peace back to be rebuilt or fixed? I know i would.
Solid Edge V20
RE: Help determining proper symbol
Circularity is the appropriate geometric characteristic to refine the circularity (sometimes described as roundness) of a hole. The elliptical hole that was described would have a Circularity value of 0.002.
However, there might be other options. One of them would be to enforce the size tolerance that was specified! If the diameter is measuring 9.002 in one direction, it's out of tolerance. Am I missing something here?
The dimensioning and tolerancing on the drawing looks like it was generally done to the ANSI Y14.5-1982 standard, although no standard is referenced in the title block. There are certain rules in that standard that apply to size tolerances. An important one is Rule #1, in which a size tolerance indirectly controls the form of the feature. Your may want to consider referencing a specific standard.
Evan Janeshewski
Axymetrix Quality Engineering Inc.
www.axymetrix.ca
RE: Help determining proper symbol
On a side note, you should remove the RFS modifier from your parallelism callout. It does not apply. You should also remove it from the positional FCF's on both places where they reference datums A and C. Datum shift modifiers are only valid on datum features of size.
Powerhound, GDTP T-0419
Production Manager
Inventor 2009
Mastercam X3
Smartcam 11.1
SSG, U.S. Army
Taji, Iraq OIF II
RE: Help determining proper symbol
RE: Help determining proper symbol
KENAT,
Have you reminded yourself of FAQ731-376: Eng-Tips.com Forum Policies recently, or taken a look at posting policies: http://eng-tips.com/market.cfm?
What is Engineering anyway: FAQ1088-1484: In layman terms, what is "engineering"?
RE: Help determining proper symbol
As Powerhound says, your GD&T feature control frames show that no real standard is being followed, and your datum B, if it had a circularity, callout, might still be wrong, since the part would most likely violate perfect form at MMC, as it now violates Rule 1.