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| I have a GD&T implementaion question | |||
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| Posted by: Mark V.P. ® 03/23/2006, 14:46:17 Author Profile eMail author Edit |
Hi, I have a GD&T implementaion question. I have established a primary datum set on my part with the surface (3 points, datum A) a weld stud (the diameter, both directions, 4-way, datum B) and a second stud ( the diameter, 2 points, 2-way anti-rotation, datum C). I have toleranced the 4-way locator to a positional tolerance of 1.0mm with respect to datum A. Her is my question, I tolerance a square opening on the surface of datum A with a profile of 0.25mm, can I do that? This the supplier of the part states that the 1.0mm positional tolerance makes it impossible to meet the 0.25 profile tolerance on the square opening. Is there a rule that states that the tolerances must be smaller than the tolerances to setup the datum set? Thanks in advance for your assistance. Regards, Mark V.P. |
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| Re: I have a GD&T implementaion question -- Mark V.P. | Post Reply | Top of thread | Forum |
| Posted by: traingdt ® 03/23/2006, 15:49:55 Author Profile eMail author Edit |
There is no problem in indicating a 0.25 tolerance for the profile. (I presume that the profile will be held with respect to A, B, and C.) Profile controls shape and the shape may be especially important in this case. Depending on the datums referenced, it often controls location and orientation also.
Just a couple of side notes: You should change the position callout of the 4-way hole to perpendicularity, since that is the only relationship it can have to datum A. There's no need to use position, since B is the datum that other features will be positioned to! Also, you need to consider if the datum references for B and C need the MMC modifier when mentioned in other callouts. This would make sense if the application allows for any looseness around B and C. If they are to be tight or press-fit, then do not use the MMC modifier. |
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| Posted by: Mark V.P. ® 03/23/2006, 16:00:47 Author Profile eMail author Edit |
Thanks for the reply. Regarding the datum B, I understand and will use perp from now on. Yes, the profile is WRT A, B and C. The supplier stated that all the 0.25mm tolerance is used up due to the large (1.0mm positional tol.) on datum B. This seems logical but I was not sure if it was a bad practice or illegal. Modified by Mark V.P. at Thu, Mar 23, 2006, 16:13:00 |
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| Posted by: Mark V.P. ® 03/23/2006, 15:56:54 Author Profile eMail author Edit |
Thanks for your reply. I would like to speak in a little more detail and show you the drawing. Is there an email in which I can reach you or a hone number? Modified by Mark V.P. at Thu, Mar 23, 2006, 15:57:15 |
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