Dimension Inspection
Dimension Inspection
(OP)
Using standard ASME Y14.5M.
So I have a drawing callout for dimension inspection 2.000". This part is, let say, its round.
How should I measure this part?
--X is having the part sitting on a surface plate, then using the height gage or CMM to measure the value. Origin value is reference to the surface plate.
--Y is using either caliper or CMM to measure its thickness value,
Which is correct?
Thanks in advance!
So I have a drawing callout for dimension inspection 2.000". This part is, let say, its round.
How should I measure this part?
--X is having the part sitting on a surface plate, then using the height gage or CMM to measure the value. Origin value is reference to the surface plate.
--Y is using either caliper or CMM to measure its thickness value,
Which is correct?
Thanks in advance!





RE: Dimension Inspection
-- actual local size (at various places)
-- actual mating envelope
From what I can see, neither X nor Y is doing either of those.
John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems
RE: Dimension Inspection
It is a requested inspection dimension, no actual mating envelop is given.
RE: Dimension Inspection
And under ASME Y14.5 "size" dimension is an "envelope" dimension - it controls both form and size. See Para 2.7 in 2009 edition.
"For every expert there is an equal and opposite expert"
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RE: Dimension Inspection
Refer back to the standard and comments, to my understanding, it seems "X" measurement is the correct approach, because it covers the form and size.
But according to Belanger, it is not right. What had I interpret wrong? Please help.
RE: Dimension Inspection
But I'm assuming it's just a regular size dimension (height, for instance). In that case, the inspector needs to measure the two categories of size mentioned in my first post:
-- The "actual local size" can be measured with calipers, a micrometer, even a CMM. This should be done at various stations along the length of the part (the number of places to measure this is somewhat subjective). Each of these measurements must be within the size range allowed by the given tolerance.
-- Then the "actual mating envelope" must be measured; this is the overall size of the part throughout its full span, and thus it controls form, as CheckerHater mentioned. This can be measured with a CMM, with some sort of customized "go" gage, or another manual method. This "actual mating envelope" must be within the size range allowed by the given tolerance.
Once these two qualities are verified, we can say that the part passes the size tolerance. But in either of the things that I've described, there is (usually) no concern about wiggling the part up and down at different angles, which seems to be what your picture is asking.
John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems
RE: Dimension Inspection
I am having problem of expressing.
RE: Dimension Inspection
I notice you never actually mentioned a tolerance. It's certainly what I would first assume when you talk about inspecting a dimension, but I suppose sometimes a tolerance is not involved. If that's the case here, then ASME Y14.5 may not be terribly relevant.
Otherwise, if a size tolerance is involved, then I think the previous answers are what you need.
- pylfrm
RE: Dimension Inspection
The print callout to inspect and report this dimension.
RE: Dimension Inspection
Thanks!
RE: Dimension Inspection
John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems