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Asme y14.5-2009

acgarcia
Good Morning,

Where does it state in the standard ASME Y14.5 that the tolerance in the feature control frame is that total tolerance and not ± tolerance? I have a drawing that calls for cylindricity at 0.0005" but I over heard the engineers talk and mention that its ±0.0005" with a total of 0.001".
  • Good Morning,

    Where does it state in the standard ASME Y14.5 that the tolerance in the feature control frame is that total tolerance and not ± tolerance? I have a drawing that calls for cylindricity at 0.0005" but I over heard the engineers talk and mention that its ±0.0005" with a total of 0.001".

    I don't think the blanket statement of tolerance you are seeking exists in the standard, (although I will gladly redact that if someone can point it out), However the fact is sorta self-evident in that all descriptions both textual and figuratively in the standard make it clear.

    For the case of cylindricity I would refer you to Section 5.4.4 on page 95 and especially to Figure 5-12 on page 96, which clearly shows the tolerance in the FCF is the total width of the tolerance zone, not ±.

    ymmv & HTH
    Sunglasses
  • Refer them to PAGE 24. SECTION 2.2 DIRECT TOLERANCE. METHODS. There are 3 types. 1) Limit Dimensioning ( high / low ) 2) PLUS / MINUS 3 ) Geometric. When you have a Geometric TOL. The # listed is the Tolerance. This is really spelled out on page 45 section 3.4.1 as well under feature control frames.

    Section 5.3 / 5.4.1 / 5.4.1.1. / 5.4.2 / Sooooo many examples where it explains that your tolerance is relating to the size of the ZONE that the feature must lie in 100%.

    Bottom line in GD&T is The tolerance in the feature control frame ( regardless symbol ) is the value of the size of the tolerance zone. ( not complicating this conversation with modifiers ) .
  • , I understand it as the total tolerance but think management is misinterpreting it as a + or -. They refer to this callout as 0.001" total as they are discussing it yet write it in the drawing as 0.0005". I scanned over the whole standard and couldn't find anything in text about how the total tolerance is in the feature control frame.

    We are going to have a meeting about this and I wanted to make sure I have the correct info when I tell them they made a mistake.
  • It may come down to how they are "picturing" it. There is a .0005 tolerance all around the cylinder. So there is .0005 on one side of the diameter and .0005 on the other side of the diameter. That give a total of .001 variation as a diameter, which is how some people think about roundness or cylindricity, not saying that is correct.
  • It may come down to how they are "picturing" it. There is a .0005 tolerance all around the cylinder. So there is .0005 on one side of the diameter and .0005 on the other side of the diameter. That give a total of .001 variation as a diameter, which is how some people think about roundness or cylindricity, not saying that is correct.

    Section 5.4.4 has a nice NOTE: "The cylindricity tolerance is a composite control of form that includes circularity, straightness, and taper of a cylindrical feature" - in other words, it ain't just about the diameter.
    Sunglasses
  • in reply to acgarcia
    Spell this out simple and use this to splain it to them. Page 24 section 2.2. spells out the 3 types of tolerances and page 45 section 3.4.1 ( fig 3.4 ) splains the feature control frame and the tolerance in that frame refer back to # 3 on page 24 section 2.2. A geometric tolerance is the size of the " zone " allowed.
  • The number is the difference of radius between two perfect cylinders in which all the measured hits must be placed, without any idea of the diameter (form only !).
    I would just ask to the management how they construct a negative difference Slight smile ...
  • Didn't read into this to much, Don't have time. I believe The Standard at the beginning of the book tell you to relate to the ASME Y14.5 M-1994 Mathematical Definition of Dimensioning and Tolerancing Principles. Don't know if this helps Pages 36-39

    http://sylvain.anselmetti.free.fr/be...olerancing.pdf
  • The engineer looked up the spec as saw what I was trying to explain and agreed that the tolerance zone is 0.0005 all the way around the cylinder, not one side to the other equaling 0.001". The drawing is being updated to 0.001".....
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