Flatness callout at cross sectional view
Flatness callout at cross sectional view
(OP)
One of the drawing has a flatness callout at cross section view as shown.
My interpretation is the flatness suppose to apply to entire surface/plane. Use the CMM to measure and obtain the flatness result by probing several points along that circular plane.
One of my colleague stated that this flatness is only apply to a small sections from point 1 to point 2, not along the entire circle. As this part chucked to the lathe, this surface should be flat.
Any comments?
My interpretation is the flatness suppose to apply to entire surface/plane. Use the CMM to measure and obtain the flatness result by probing several points along that circular plane.
One of my colleague stated that this flatness is only apply to a small sections from point 1 to point 2, not along the entire circle. As this part chucked to the lathe, this surface should be flat.
Any comments?





RE: Flatness callout at cross sectional view
"Know the rules well, so you can break them effectively."
-Dalai Lama XIV
RE: Flatness callout at cross sectional view
John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems
RE: Flatness callout at cross sectional view
Your colleague needs better understanding of basic geometry.
"For every expert there is an equal and opposite expert"
Arthur C. Clarke Profiles of the future
RE: Flatness callout at cross sectional view
________________________________
Ryan M
Quality Engineer
3d Printer Hobbyist
RE: Flatness callout at cross sectional view
Following is off topic: He said it should be a parallelism callout instead of flatness-->so when this part is on CMM, then you will get a correct reading....
Is he right on this? My understanding is CMM measure the flatness or the flatness callout is regardless of how the part is oriented or shape.
RE: Flatness callout at cross sectional view
"Know the rules well, so you can break them effectively."
-Dalai Lama XIV
RE: Flatness callout at cross sectional view
Yes, CMM, when programmed properly, should be able to measure flatness of inclined surface, but it depends on what kind of CMM and what kind of person operates it.
Yes, it's important to start with the function of the part. By the way, if your part serves as some sort of spacer, being "sandviched" between two other parts, it may be beneficial to specify Parallelism as well.
So, it's all up to you. Good luck!
"For every expert there is an equal and opposite expert"
Arthur C. Clarke Profiles of the future
RE: Flatness callout at cross sectional view
It's generally not a good idea to specify parts based on machine capabilities rather than function. This also applies to inspection. Your colleague's suggestion that you should specify parallelism instead of flatness because it will give you a good reading, is misguided at best. Your CMM can calculate flatness providing it's not a 30 year old CMM. It is function that should drive the specification. I agrre with CheckerHater that your colleague needs a much better understanding of GD&T and it's application.
John Acosta, GDTP S-0731
Engineering Technician
Inventor 2013
Mastercam X6
Smartcam 11.1
SSG, U.S. Army
Taji, Iraq OIF II
RE: Flatness callout at cross sectional view
From experience, it's not that difficult to make a conical surface on the lathe without intending to do so. Most often, excessive tool or toolpost flex/movement is the culprit, but there are other ways.
RE: Flatness callout at cross sectional view
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The Help for this program was created in Windows Help format, which depends on a feature that isn't included in this version of Windows.
RE: Flatness callout at cross sectional view