drawings with dimensions to theoretical intersections and metrology
drawings with dimensions to theoretical intersections and metrology
(OP)
When I get a print from a customer with obtuse or acute bends I immediately look to see how they dimension the bend locations. If they are dimensioning the intersection points I request them to change to the center of the bend radius. The intersection points are not a physical location, they are in space and cannot be controlled. In order to get these measurements accurately you need to use a CMM. With a gage pin and a height gage I can measure where the center of the bend is. Does anyone know of an ANSI spec, or something from ASQ that agrees with this? I know dimensioning to intersection points is a commonly accepted practice, but it makes it difficult when trying to actually make parts. I believe this is a point where what is easy on paper isn't so easy to reproduce in the real world. Any insight will be appreciated.





RE: drawings with dimensions to theoretical intersections and metrology
RE: drawings with dimensions to theoretical intersections and metrology
Tolerancing to virtual sharps is supported in section 1.7.2 of the 1994 version of ASME Y14.5M.
If you asked me to change my dimension scheme from intersection points I'd probably say no but might vary depending on the exact tolerance scheme.
What is Engineering anyway: FAQ1088-1484: In layman terms, what is "engineering"?
RE: drawings with dimensions to theoretical intersections and metrology
I have dealt with customers that didn't want to change the drawing. When that happens I send them a price for making the parts to their drawing, or a no quote. I also send them a price if they change the drawing to the scheme I am asking for. If they want the cheaper price they change the drawing. If not, find someone else to deal with the headache of chasing dimensions that are in space and can't be controlled.
This is one of those area's that just because it's easy on paper, it doesn't translate to the real world. Centers of bends and radii can be found. Intersection points are theoretical and therefore are open to inconsistencies. As a manufacturing engineer that's what I'm trying to eliminate.
RE: drawings with dimensions to theoretical intersections and metrology
The intersection can easily be found and measured with a couple of straight edges or scales, the center of the bend, not so much.
Regards,
Mike
The problem with sloppy work is that the supply FAR EXCEEDS the demand
RE: drawings with dimensions to theoretical intersections and metrology
Once you dimension to the center of the bend radius the size tolerance on the radius starts to play into the overal size, if overall size is critical then I have to tighten the other tolerances accordingly so while the part may be easier to measure it can become harder to meet required tolerance.
What is Engineering anyway: FAQ1088-1484: In layman terms, what is "engineering"?
RE: drawings with dimensions to theoretical intersections and metrology
I was talking about parts where you need one or two made, you need an angle or a channel formed, and about all you are interested in is the leg dimensions and angle.
Regards,
Mike
The problem with sloppy work is that the supply FAR EXCEEDS the demand
RE: drawings with dimensions to theoretical intersections and metrology
What is Engineering anyway: FAQ1088-1484: In layman terms, what is "engineering"?
RE: drawings with dimensions to theoretical intersections and metrology
The problem with sloppy work is that the supply FAR EXCEEDS the demand