Profile of a surface (GD&T)
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Posted by: jevanpe5 ® 11/17/2009, 10:05:42 Author Profile eMail author Edit

Hi all, I'm a tool maker for Medtronic in Warsaw, In. (greatest job ever, by the way) An engineer friend of mine drew up a series of little, very simple gauges and gave them to me to make. Tolerances are pretty close. Wait... very close. Anyway, I'll try to say this simple without having to post a pic. In this gauge, theres a 3.900 mm diameter hole. Tolerencing block says that a 3 place dimension is +/- .005 mm. Then he has an "inside unilateral profile of a surface mark" (the profile circle inside the true diameter) with an arrow pointing to one inside edge of the profile circle and the other arrow to the outside of the true diameter. The spec on that is .008 mm. My question is; Would I interperate this as +/- .005 mm on the diameter making sure that the profile edges do not fall beyond the profile dimension he gave? Or do I interperate this as my diameter can be anywhere between 3.900 mm. to 3.884 mm. (remembering that the .008 dim. he gave was for only one wall thickness between the true part diameter and the prfile circle he drew... so, 2 walls equals .016 mm.) Am I to understand that he is controlling the diameter with the Profile mark? Or is it saying that the hole is still .005 mm but not allowed to fall inside the parameters of the profile note?

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: Profile of a surface (GD&T)
: Profile of a surface (GD&T) -- jevanpe5	Post Reply	Top of thread	Engineering Forum

Posted by: traingdt ® 11/17/2009, 10:15:03 Author Profile eMail author Edit

If everything is just as described, there is an inherent conflict in the way that hole is toleranced. If a profile tolerance is given on a hole, the "true" diameter of the hole must not have its own tolerance. This is usually indicated by placing a box around that 3.900 dimension (it's then called a basic dimension). Is there a box? Or perhaps another note on the drawing that addresses numbers not directly toleranced? Profile can sometimes be used to control shape only, but when applied to a full circle, it automatically does the job of controlling size as well. John-Paul Belanger Modified by traingdt at Tue, Nov 17, 2009, 10:16:37

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Posted by: jevanpe5 ® 11/17/2009, 10:22:30 Author Profile eMail author Edit

He placed the box around the 3.900. Thanks, but.. hehe, guess I lost the money on that one. My question to Shane was, "why put a dimension on a hole, when you can just throw a GD&T profile mark on it and say.... yea, plop one in there somewhere." I thought that notation would mean the profile should not deform or move in any way through the profile circle he drew on the inside... Thanks, John... (but I'm not use to being wrong.... hehe, not with him anyway.) I'll get him next time. Thanks again.

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Posted by: traingdt ® 11/17/2009, 10:41:46 Author Profile eMail author Edit

No sweat -- even with GD&T designers sometimes make things confusing, don't they? But yes, by putting a box around the 3.900, it effectively says "ignore the default tolerance in the title block and only use the GD&T specification."

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