Number of inspection places for width callout
Number of inspection places for width callout
(OP)
I have a fairly simple callout for the width of a glass sheet (319.173 +/- 0.5 mm, one edge parallel to opposite edge within 0.3 mm). I am wondering if there is a minimum number of locations that the width needs to be measured. Are they required to run a probe down the whole edge and report the max and min? Is there a minimum number of locations to measure parallelism? If the edge is curved (i.e. the corners are even, but it bows in at the middle), would it still be called parallel? Is the parallelism "best fit edge" created by finding the high points on the edge (taking a plate and resting it on the edge, essentially) or is it created by some kind of weighted average of a bunch of points?
Whew, lots of questions. Thanks in advance for any responses.
Laura
Whew, lots of questions. Thanks in advance for any responses.
Laura





RE: Number of inspection places for width callout
thread1103-217299: Flatness/Parallelism Question was most recent, there was one a few months ago where I put more from the standard but I haven't been able to relocate it recently, may have got wiped for copyright reasons.
KENAT, probably the least qualified checker you'll ever meet...
RE: Number of inspection places for width callout
This should apply to any/most drawing standards.
RE: Number of inspection places for width callout
I have a fairly simple callout for the width of a glass sheet (319.173 +/- 0.5 mm, one edge parallel to opposite edge within 0.3 mm).
I am wondering if there is a minimum number of locations that the width needs to be measured. No
Are they required to run a probe down the whole edge and report the max and min? No
Is there a minimum number of locations to measure parallelism? No
If the edge is curved (i.e. the corners are even, but it bows in at the middle), would it still be called parallel? Possibly
Is the parallelism "best fit edge" created by finding the high points on the edge (taking a plate and resting it on the edge, essentially) or is it created by some kind of weighted average of a bunch of points? Neither
The parallelism requirement is that all points on the toleranced edge must lie within a zone 0.3 mm thick. That zone is defined to be parallel to the "true geometric counterpart" of the datum edge, physically represented by a surface plate resting on the datum edge.
Strictly speaking, the requirement is that all points lie within the tolerance zone. The method used to verify this, and the number of points sampled, is up to the inspector.
Evan Janeshewski
Axymetrix Quality Engineering Inc.
www.axymetrix.ca
RE: Number of inspection places for width callout
Thanks a lot for the quick answers, it helps.
RE: Number of inspection places for width callout
This is normally part of the quality plan or something, which may contain an annotated/marked up drawing.
KENAT, probably the least qualified checker you'll ever meet...
RE: Number of inspection places for width callout
Matt Lorono
CAD Engineer/ECN Analyst
Silicon Valley, CA
Lorono's SolidWorks Resources
Co-moderator of Solidworks Yahoo! Group
and Mechnical.Engineering Yahoo! Group
RE: Number of inspection places for width callout
There's always inspection fixtures...
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RE: Number of inspection places for width callout
RE: Number of inspection places for width callout
RE: Number of inspection places for width callout
KENAT, probably the least qualified checker you'll ever meet...
RE: Number of inspection places for width callout
V
RE: Number of inspection places for width callout
The reason for that is that a 'narrow edge' as in your case does not lend itsself well to a datum feature. I realize you did nost specify the thickness, but my assumption is 1/8 - 1/4 in. or so.
RE: Number of inspection places for width callout
I'm curious. How does the use of profile of a surface imply that they would measure at more than one place? Or that the original size and parallelism callouts would only be measured at one place?
Evan Janeshewski
Axymetrix Quality Engineering Inc.
www.axymetrix.ca
RE: Number of inspection places for width callout
It doesn't--directly. But any inspection of profile of surface that I've ever seen has the inspector running an indicator down the surface in question more than once to get a reliable reading. This is common sense--not necessarily standard, however. Parallelism seems to be more of a lax requirement than profile of surface in the eyes of the inspection department, from my experience.
I should've prefaced my initial comment with, "Assuming a flatness callout on the primary datum, and a competent inspector, one may opt for a profile of surface on the parallel surface..."
V
RE: Number of inspection places for width callout
The edge controlled can't vary more than 0.3, and it's the inspectors job to verify that, assuming your inspection is competent.
If your worried about abrupt changes within the 0.3 boundary or (say) a convex bow in the middle, then you need to control the form (straightness) tighter than 0.3 or modified per unit length
RE: Number of inspection places for width callout