Proper Callout for Hole Centered on Internal Bore?
Proper Callout for Hole Centered on Internal Bore?
(OP)
I have a part that has an internal bore with a small hole at the bottom of the bore. I want the hole at the bottom to be geometrically concentric with the diameter of the bore, because the mating part locates off the bore and slides into the smaller hole. If the hole is too far off of the centerline, the mating part won't fit correctly.
What is the correct GD&T callout to locate the small hole? Common sense says concentricity, but everything I've read says to not confuse GD&T concentricity with actual geometric concentricity (or co-axialarity) and to avoid it like the plague. Runout doesn't seem correct because I (within reason) don't care about the shape of the bore, just the centerline location. Should the hole be true position relative to a datum set by the bore?
What is the correct GD&T callout to locate the small hole? Common sense says concentricity, but everything I've read says to not confuse GD&T concentricity with actual geometric concentricity (or co-axialarity) and to avoid it like the plague. Runout doesn't seem correct because I (within reason) don't care about the shape of the bore, just the centerline location. Should the hole be true position relative to a datum set by the bore?





RE: Proper Callout for Hole Centered on Internal Bore?
Is the mating part intended to have a clearance fit with both the larger bore and the smaller hole? If so, then you should probably be concerned with the actual surfaces of the features, not imaginary centerlines.
One way to accomplish this is to apply a position tolerance at MMC to the small hole, referencing the larger bore as primary (and only) datum feature at MMB. Both features would have diameter tolerances set based on the fit requirements and the tolerances of the mating part.
pylfrm
RE: Proper Callout for Hole Centered on Internal Bore?
RE: Proper Callout for Hole Centered on Internal Bore?
An alternate would be profile tolerance since you are concerned with a fixed boundary to avoid eclipsing the view port.
RE: Proper Callout for Hole Centered on Internal Bore?
John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems