![]() ![]() ![]() A datum is defined as a theoretically perfect plane, axis, or point from which measurements will be made. Think of it this way: A datum doesn't exist on a part. For argument sake lets say A,P3 and P4 are the frame of reference and go from there, since I cannot ask the individual who made the drawing 10 years ago, why.ĭoug RE: datum reference frame and profile Belanger (Automotive) 2 Apr 13 09:53 I ask these question for my own personal knowledge and would not like to have this spin off in another direction. Can you explain why P1 though P4 cannot be referenced as individual targets in a control frame? How can you only reference one datum in a feature control frame if you are tolerancing something like true position or profile of a surface? How come you can't have an "M" modifier when referancing P1? It's a dowel pin and has a MMC (FYI, they had an MMC callout to P3 on the. All basic dimension are from P1 which is the intersection of P3 and P4 and there is no positional tolerance applied to this location. P1 and P2 are dowel pins and I think they labeled them solely to generate datums P3(P1P2) and P4(P1_P2). The only exception is on the drawing P3 is labeled as P1P2 and P4 is labled as P1_P2. I am unable to publish the actual drawing. Yes, this an accurate (even though basic) representation of the drawing and this is how all these features are called out. pleas chime in, any and all feedback is greatly appreciated.ĭoug RE: datum reference frame and profile Belanger (Automotive) 1 Apr 13 23:27 Our second debate is, he is establishing datum C from the part itself but, I see datum C as being "implied" and should be established using basic dimensions to create theoretical plane because it is there to establish location of the tolerance zone. I said it is possible because the 5.250 will move with any deviation of this surface and the 5.250 is a secondary control of form. I don't see it this way, the print specifies "dimensioning and tolerancing IAW asme y14.5m-1994. 019 on datum c because it violates the +/-.005 tolerance. ![]() Our Process engineer who also controls our OGP SmartScope says that you cannot have a profile of. 019 profile of a surface to datum C and how it is referenced to the. As I see the part the datum reference frame is established by A, P3 and P4 since hole P1 has no positional tolerance and notes on the drawings indicate as such. I hope someone can clarify an ongoing debate on interpretaion of a print.The attached print is a basic representation of an actual part and shows the features in question. ![]()
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