# Thread: Problem understanding those callouts

1. ## Problem understanding those callouts

Looking for explanation of those callouts. Diameter 30 +/- 0.25 and cylindricity of 0.2 apply to the same feature. What is the purpose of having both? Wouldn't be enough to just have 30 as a basic with cylindricity callout? Why is 80 basic and 100 not? Are those 2 positional callouts same as saying parallel to A?

2. Assuming this is an ASME or ANSI engineering drawing...

The 30 +/- 0.25 limits the form to 0.50 by Rule #1 and the Cylindricity of 0.2 limits the variations of form to 0.2 on radius or 0.40 on diameter.

The cylindricity is a refinement of size and the form allowed by Rule #1..

The limits of size and cylindricity specifications do different things...

3. Thank you Kelly, any inputs on second part of my question?

4. Originally Posted by newone
Thank you Kelly, any inputs on second part of my question?
Yes, what is the engineering drawing standard? ISO or ASME?

5. Asme

6. Originally Posted by newone
Asme
It's a miss-application.. Position tolerance is only allowed on a feature of size per. ASME Y14.5-2009, paragraph 7.2.

Honestly, on second look the drawings geometric (geometrical) tolerancing is annotated like an ISO 1101 drawing. In ISO 1101 a position tolerance is allowed on a feature without size. In this case it would function like an ASME Profile of surface specification.

7. Kelly -- I'm curious about why you think it looks like an ISO drawing. (Other than the fact that position is used on a surface.)
I ask because the ISO drawings I've seen usually have the leader line pointing to the surface at a normal (perpendicular) angle. But maybe ISO allows for the slanted leader?

8. Originally Posted by Belanger
Kelly -- I'm curious about why you think it looks like an ISO drawing. (Other than the fact that position is used on a surface.)
I ask because the ISO drawings I've seen usually have the leader line pointing to the surface at a normal (perpendicular) angle. But maybe ISO allows for the slanted leader?
The leader line drafting method is very much used within the ISO standards prior to 2009 and then the application of the position tolerance to control the surface. I'm thinking that the engineering drawing may actually be an ISO standard document or created by somebody experienced in that standard..

We'll see

9. ASME is my best guess, does not say on the drawing. It uses 3rd angle projection, size listed like that: B (A3) but general tolerances in the notes are to DIN 16901-150.

10. 3rd angle projection is allowed on ISO documents as is first angle projection on ASME documents. DIN - is a German standard and DIN 16901-150 is simply a rewrite of ISO 16901-150.

You should verify the engineering drawing standard used on this document...

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