Hello to you all, I am new to this forum.

I try to find experts for the ISO drawing standard, I hope I am in the right place.

Here are a few questions :

1. First I would like to know, if I put a dimension, let say a diameter of a cylinder with a tol. of 0/-0.2. does it means that the straightness of cylinder must be 0.2 or lower? or must I state the Geometrical relation along side with the tolerance, what does not make real sense.And In which Std. does this roles stated?

2. If I understand the Iso 8015 correctly, It means, if stated in the drawing title block, that the dimension's tol. do not apply for the geometric relation (as in the previous question) , hence the "Principle of independency" apply. If so, I could write diameter tol. of 0/-0.2 and straightness of 1. If what I wrote is correct than how do I measure the dimension of the cylinder?

Please refer to the following drawing:

As shown on drawing, with the ISO 8015 stated:

How to measure?, the following drawing shows the measured dimension, is it correct? what "max" dimension will still comply with the upper drawing?

I hope I have explained my self clearly ,

Thanks

I try to find experts for the ISO drawing standard, I hope I am in the right place.

Here are a few questions :

1. First I would like to know, if I put a dimension, let say a diameter of a cylinder with a tol. of 0/-0.2. does it means that the straightness of cylinder must be 0.2 or lower? or must I state the Geometrical relation along side with the tolerance, what does not make real sense.And In which Std. does this roles stated?

2. If I understand the Iso 8015 correctly, It means, if stated in the drawing title block, that the dimension's tol. do not apply for the geometric relation (as in the previous question) , hence the "Principle of independency" apply. If so, I could write diameter tol. of 0/-0.2 and straightness of 1. If what I wrote is correct than how do I measure the dimension of the cylinder?

Please refer to the following drawing:

As shown on drawing, with the ISO 8015 stated:

How to measure?, the following drawing shows the measured dimension, is it correct? what "max" dimension will still comply with the upper drawing?

I hope I have explained my self clearly ,

Thanks

Referring to the picture, the part consists of a hole extruded through a rectangular plate and is located with basic dimensions, with respect to datum B and C (shown in the picture). Datum A, B, and C are primary, secondary, and tertiary datums respectfully.

My question is, if a positional control is applied to the circular feature of size, then why is datum A referenced in the FCF? To me, datum A is irrelevant for the reasons I mention in the following:

What I’m trying to point out, in 1-2, is that the main features, true position & tolerance zone, that define the positional control have nothing to do with datum A.

The only__reason__ I can think of for controlling the location relative to datum A is because datum B is typically oriented with respect to datum A, and C to A and B. Therefore datum A must be referenced because the orientation of datum B to A and C to B & A will affect the accuracy of locating the FOS to its intended true position. BUT if this is the case, then why do books on tolerance analysis not take this into account? My “__reason__” for why datum A is consider is no longer making sense, given the statement in the previous sentence.

Can someone help me make sense of all this?

Thank you.

My question is, if a positional control is applied to the circular feature of size, then why is datum A referenced in the FCF? To me, datum A is irrelevant for the reasons I mention in the following:

- The focus is to control the position of the feature which is located with respect to datums B and C alone.
- The positional tolerance zone resides within a region measured about true position relative to datums B and C.

What I’m trying to point out, in 1-2, is that the main features, true position & tolerance zone, that define the positional control have nothing to do with datum A.

The only

Can someone help me make sense of all this?

Thank you.

Is Datum B valid?

OK, I'll admit it. GD&T is foreign to me.

Is the (attached) dimension ±.002 or .002 Max?

Is the (attached) dimension ±.002 or .002 Max?