Basic Dimensions and General Feature Control Frame

Then they tell me to take the tolerance in the profile FCF in the general notes and apply it to the basic dimension.

You can't really get away with thinking about GD&T concepts in the same mindset as coordinate dimensions, which is, it seems to me, what this statement is implying.

You need to think about GD&T in terms of a zone within which the feature must reside. The basic dimensions tell you where the middle of the zone is(assuming that you have an equal bilateral tolerance, which is the most common situation.)

Imagine that you are making a drawing and you must use only the basic dimensions provided plus implied parallelism/coaxiality and implied perpendicularity(if the basic dimension would be 0 or 90 it doesn't need to be specifically called out) to create the shape. Once you have created whatever shape the basics describe you must offset it to create the zone that the feature must reside in. The offset value is equal to half of the value shown in the feature control frame.

So if the number in there is .030 you would offset the shape that you have drawn by .015 on each side. This gives you the tolerance zone that the measured feature must fit inside. If you make a few sketches you will soon realize that offsetting a shape by .015 on each side is not the same thing as applying a +/- .015 tolerance to all of the basic dimensions that went into creating that shape. The result could be the same in a few limited circumstances but generally it will not be the same.

If these concepts are new to you, or you haven't been exposed to them for some time, then a GD&T course will be worth it's weight in gold. There is a ton of information available online from sites like Tec-ease and companies like Effective Training International have published some great books and self study courses.

Then they tell me to take the tolerance in the profile FCF in the general notes and apply it to the basic dimension.

You can't really get away with thinking about GD&T concepts in the same mindset as coordinate dimensions, which is, it seems to me, what this statement is implying.

You need to think about GD&T in terms of a zone within which the feature must reside. The basic dimensions tell you where the middle of the zone is(assuming that you have an equal bilateral tolerance, which is the most common situation.)

Imagine that you are making a drawing and you must use only the basic dimensions provided plus implied parallelism/coaxiality and implied perpendicularity(if the basic dimension would be 0 or 90 it doesn't need to be specifically called out) to create the shape. Once you have created whatever shape the basics describe you must offset it to create the zone that the feature must reside in. The offset value is equal to half of the value shown in the feature control frame.

So if the number in there is .030 you would offset the shape that you have drawn by .015 on each side. This gives you the tolerance zone that the measured feature must fit inside. If you make a few sketches you will soon realize that offsetting a shape by .015 on each side is not the same thing as applying a +/- .015 tolerance to all of the basic dimensions that went into creating that shape. The result could be the same in a few limited circumstances but generally it will not be the same.

If these concepts are new to you, or you haven't been exposed to them for some time, then a GD&T course will be worth it's weight in gold. There is a ton of information available online from sites like Tec-ease and companies like Effective Training International have published some great books and self study courses.