yang686526

diameter callout on drawing
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?
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.

paul:
can you believe but i absolutely agree with you in your statement.
dave d.
dave, i knew that you would agree with me sooner or later.
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.
honesty may be the best policy, but insanity is a better defense.
if the part must be within the tolerance callout only at it max size, what is the purpose of the lower limit?
i agree with the others that limits are just that.
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)
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
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powerhound,
yes, i've been a bit off here, mixing tp with issue, viewing thread too fast. sorry for that
the more i think on it, the sillier it seems. if you have no min limit, why even bother to put a hole in? cheaper and faster!
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