What exactly does the datum feature tell us?
A datum is theoretically perfect. It takes some getting used to, but if you were to say, on your drawing, apply a datum to the bottom surface of your plate, then in practice, you would then set your plate on a granite inspection plate (or something similar). Then the granite inspection plate becomes your actual datum plane.
Read the link that posted (in it's entirety). It has lots of examples.
I will suggest some training on GD&T as datums are but a fraction of this methodology.
Thank you. In a nut shell, how would you identify a datum.
Matt Calzone wrote: Thank you. In a nut shell, how would you identify a datum.
Matt Calzone wrote:
A datum "identifies features for establishing relationships imposed by by geometric tolerances and for constraining degrees of freedom".
Datums are "theoretical exact points, axes, lines and planes".
A datum reference frame is "three mutually perpendicular intersecting datum planes".
Can you provide an example? Does a datum have unit of measure or and specs?
Matt Calzone wrote: Can you provide an example? Does a datum have unit of measure or and specs?
No. GD&T is a deep and somewhat convoluted subject, so again:
You decide what is important. Where could be reference through out manufacturing to check size for QC.
Datum need to be reliable and repeatable. It is where all measurement start.
Do not put any datum or GD&T on your drawings until you took a GD&T course.
Adding wrong, unnecessary GD&T will make the part impossible or very costly to produce.
I have customer that put datum on drawing which is not on the part.
Datums in GD&T – GD&T Basics
Matt, the subject is EXTENSIVE. This forum is not the right place to discuss things, especially ones as basic as "What is a datum?" Do yourself a favor and start with the link Dan posted. Then find a class online to learn more.
If you persist with your questions here you will get flamed.
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