I have a dimension on a print with the diameter symbol as a prefix. The dimension is 9.8 +.05/-.15 mm. I have always been told with this dimensional callout, that at any cross-section on this feature, the part is not allow to vilolate LMC or MMC. I am now being told that with this callout only (not using circularity or cylindricity) that the part must be within the tolerance callout only at it max size. In other words, there can be areas on the feature that are below LMC. Is there anything within the Y14.5 standard that states that a diametrical callout without circularity or cylindricity still cannot vilolate LMC and MMC?
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Diameter callout on drawing 1
- Thread starter FullerMTU
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PaulJackson
Automotive
NO! The minimum size may not be below the limit.
Furthermore if the drawing references ASME standards, the MMC size (maximum diameter in this case) must not exceed "perfect form at MMC".
If the drawing references ISO standards then the max size is a cross-sectional value unless the specification has a (E) circled "E" which then invokes the "Envelope Principle" same as ASME "perfect form at MMC".
In either case ASME or ISO the cross-sectional value of the LMC size may not exceed its limit.
Furthermore if the drawing references ASME standards, the MMC size (maximum diameter in this case) must not exceed "perfect form at MMC".
If the drawing references ISO standards then the max size is a cross-sectional value unless the specification has a (E) circled "E" which then invokes the "Envelope Principle" same as ASME "perfect form at MMC".
In either case ASME or ISO the cross-sectional value of the LMC size may not exceed its limit.
PaulJackson
Automotive
Dave, I knew that you would agree with me sooner or later.![[pipe]](/data/assets/smilies/pipe.gif "[pipe] [pipe]")
If this is the intent, perhaps use a profile. Dimension the hole at LMC or nominal and attach a profile with a bilateral zone (more tolerance on one side than the other). Make the inside tolerance large enough to accomodate large deviations.
![[bat]](/data/assets/smilies/bat.gif "[bat] [bat]")
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Centerline of the part must be within cylidrical zone; If MMC is aplied, you get some Bonus tolerance as diameter is deviating of it's smallest value( HOLE getting larger).
LMC is used when holes are near critical edges( very low material left to prevent the hole to get into outside world)
LMC is used when holes are near critical edges( very low material left to prevent the hole to get into outside world)
powerhound
Mechanical
RobNOK,
I don't know if I understood what you wrote but...bonus tolerance never applies to the size of a feature which is what were talking about here. It's the other way around. Bonus tolerance can be derived from the size of a feature when the appropriate callout is specified at MMC.
As far as the cylindrical tolerance zone goes; where are you getting that from? We are talking about the size of a feature here.
Powerhound, GDTP T-0419
Production Supervisor
Inventor 2008
Mastercam X2
Smartcam 11.1
SSG, U.S. Army
Taji, Iraq OIF II
I don't know if I understood what you wrote but...bonus tolerance never applies to the size of a feature which is what were talking about here. It's the other way around. Bonus tolerance can be derived from the size of a feature when the appropriate callout is specified at MMC.
As far as the cylindrical tolerance zone goes; where are you getting that from? We are talking about the size of a feature here.
Powerhound, GDTP T-0419
Production Supervisor
Inventor 2008
Mastercam X2
Smartcam 11.1
SSG, U.S. Army
Taji, Iraq OIF II
ImnotfromMars
Mechanical
The upper limit has to be held unless a note is added "MMC not reqd". This is Rule #1. But the lower limit does not have to be respected in certain cases. Imagine a very long banana shaped hole.
Robert
Robert
powerhound
Mechanical
ImnotfromMars,
I'm sorry but what you wrote is not correct. The upper and lower limit always have to be respected. Whatever your interpretation of Rule #1 is, it's not correct. The note that you are referring to is one of the two ways that rule #1 can be overridden and the note is: "Perfect form at MMC not required". That's a far cry from "MMC not required". MMC is not a requirement, it's a condition that all features of size have.
Powerhound, GDTP T-0419
Production Supervisor
Inventor 2008
Mastercam X2
Smartcam 11.1
SSG, U.S. Army
Taji, Iraq OIF II
I'm sorry but what you wrote is not correct. The upper and lower limit always have to be respected. Whatever your interpretation of Rule #1 is, it's not correct. The note that you are referring to is one of the two ways that rule #1 can be overridden and the note is: "Perfect form at MMC not required". That's a far cry from "MMC not required". MMC is not a requirement, it's a condition that all features of size have.
Powerhound, GDTP T-0419
Production Supervisor
Inventor 2008
Mastercam X2
Smartcam 11.1
SSG, U.S. Army
Taji, Iraq OIF II
ImnotfromMars
Mechanical
In light of what is being asked in this posting the limits are not absolute. Rule #1 is prefect from at max material condition. But in least material condition the hole is measured at different locations. In the case of a banana shaped hole (ASME fig 2.6 ) it can be seen that the way the hole is measured it can extend into least material condition area and exceed the boundaries. I believe this is what is being asked for in this post.
I appologize for my shortening of notes.
Robert
I appologize for my shortening of notes.
Robert
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1
- #14
weavedreamer
Automotive
'I have a dimension on a print with the diameter symbol as a prefix. The dimension is 9.8 +.05/-.15 mm. I have always been told with this dimensional callout, that at any cross-section on this feature, the part is not allow to vilolate LMC or MMC.'
'I am now being told that with this callout only (not using circularity or cylindricity) that the part must be within the tolerance callout only at it max size.'
The feature should measure between 9.85 and 9.65
'In other words, there can be areas on the feature that are below LMC.'
In the case of a hole, LMC would be 9.85, any larger and it should fail inspection.
In the case of a peg, LMC would be 9.65, any smaller and it should fail inspection.
'Is there anything within the Y14.5 standard that states that a diametrical callout without circularity or cylindricity still cannot vilolate LMC and MMC?'
See ASME Y14.5M - 1994 Section 2.7, 2.7.1, & 2.7.1.1
'I am now being told that with this callout only (not using circularity or cylindricity) that the part must be within the tolerance callout only at it max size.'
The feature should measure between 9.85 and 9.65
'In other words, there can be areas on the feature that are below LMC.'
In the case of a hole, LMC would be 9.85, any larger and it should fail inspection.
In the case of a peg, LMC would be 9.65, any smaller and it should fail inspection.
'Is there anything within the Y14.5 standard that states that a diametrical callout without circularity or cylindricity still cannot vilolate LMC and MMC?'
See ASME Y14.5M - 1994 Section 2.7, 2.7.1, & 2.7.1.1
- Thread starter
- #16
ImnotfromMars
Mechanical
"I am now being told that with this callout only (not using circularity or cylindricity) that the part must be within the tolerance callout only at it max size. In other words, there can be areas on the feature that are below LMC".
I believe what is meant here is if the tolerance is viewed as two absolute concentric cylinders which the profile of the part must fall between, then the statement is correct and "there can be areas on the feature that are below LMC".
"In the case of a hole, LMC would be 9.85, any larger and it should fail inspection". The calipered measurement would not exceed 9.85 yet the profile of the hole could exceed the 9.85 cylinder in some areas. Fig 2.6 illustrates this.
The above postings should have referenced ASME Y14.5M-1994 section 2.7.1.2 especially subsection "C" and Fig 2.6.
Robert
I believe what is meant here is if the tolerance is viewed as two absolute concentric cylinders which the profile of the part must fall between, then the statement is correct and "there can be areas on the feature that are below LMC".
"In the case of a hole, LMC would be 9.85, any larger and it should fail inspection". The calipered measurement would not exceed 9.85 yet the profile of the hole could exceed the 9.85 cylinder in some areas. Fig 2.6 illustrates this.
The above postings should have referenced ASME Y14.5M-1994 section 2.7.1.2 especially subsection "C" and Fig 2.6.
Robert
weavedreamer
Automotive
2.7.1.2
(c) There is no requirement for a boundary of perfect
form at LMC. Thus, a feature produced at its
LMC limit of size is permitted to vary from true
form to the maximum variation allowed by the
boundary of perfect form at MMC.
Key word appears to be boundry. The 9.85 LMC size is desling with the feature size. The difference is being below the LMC; and being outside of the LMC boundry, for which there is no requirement.
(c) There is no requirement for a boundary of perfect
form at LMC. Thus, a feature produced at its
LMC limit of size is permitted to vary from true
form to the maximum variation allowed by the
boundary of perfect form at MMC.
Key word appears to be boundry. The 9.85 LMC size is desling with the feature size. The difference is being below the LMC; and being outside of the LMC boundry, for which there is no requirement.
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