Free State with Average Diameter
Free State with Average Diameter
(OP)
Since all geometric tolerances apply in free state condition by default what is the purpose of the circle F in Fig. 6-53? I have always been under the impression that a circle F modifier is only used when there is a restraint note on the print and the specified feature is to be check unrestrained. This is why I'm okay with Fig. 6-54. There is a restraint note. Fig. 6-53 has no such note though.
My guess is that the circle F frees it from the rule that says a form tolerance must be a refinement of size tolerance but can someone confirm or deny that? In the case of 6-53 it's not a stretch for me to imagine that the high and low limit of an average is not a feature of size.
My guess is that the circle F frees it from the rule that says a form tolerance must be a refinement of size tolerance but can someone confirm or deny that? In the case of 6-53 it's not a stretch for me to imagine that the high and low limit of an average is not a feature of size.
Powerhound, GDTP S-0731
Engineering Technician
Inventor 2010
Mastercam X6
Smartcam 11.1
SSG, U.S. Army
Taji, Iraq OIF II





RE: Free State with Average Diameter
I take it you are using ASME Y14.5M-1994. I cannot find the figure in ASME Y14.5-2009.
The figure looks okay to me. It controls free state circularity, and it controls size, independent of circularity.
--
JHG
RE: Free State with Average Diameter
John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems
http://www.gdtseminars.com
RE: Free State with Average Diameter
Powerhound, GDTP S-0731
Engineering Technician
Inventor 2010
Mastercam X6
Smartcam 11.1
SSG, U.S. Army
Taji, Iraq OIF II
RE: Free State with Average Diameter
So could one safely infer that the opposite applies to non-rigid parts - that dimensions and tolerances apply in the restrained state? I never thought of it that way but I guess it does make sense.
Powerhound, GDTP S-0731
Engineering Technician
Inventor 2010
Mastercam X6
Smartcam 11.1
SSG, U.S. Army
Taji, Iraq OIF II
RE: Free State with Average Diameter
John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems
http://www.gdtseminars.com
RE: Free State with Average Diameter
RE: Free State with Average Diameter
I'm specifically referring to figure 6-53 to which there is no restraint called out but the free state modifier is in the FCF.
The reason the question was asked was because I had a print come across my desk with the AVG diameter with a circularity callout in the free state. The problem was that it was a rigid part so I thought maybe there was something I was missing. It turns out the guy was trying to allow more circularity error than the size tolerance. I wound up telling him to add the note "PERFECT FORM AT MMC NOT REQUIRED" to that feature.
Powerhound, GDTP S-0731
Engineering Technician
Inventor 2010
Mastercam X6
Smartcam 11.1
SSG, U.S. Army
Taji, Iraq OIF II
RE: Free State with Average Diameter
Keep in mind that "PERFECT FORM AT MMC NOT REQUIRED" unties form of the feature (pin) along its axis too. So you it will not only loosen up circularity but also axis straightness (unless there is additional callout on the print limiting the straightness).
RE: Free State with Average Diameter
Powerhound, GDTP S-0731
Engineering Technician
Inventor 2010
Mastercam X6
Smartcam 11.1
SSG, U.S. Army
Taji, Iraq OIF II