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Thread: Position tolerance exercises

  1. #1
    Associate Engineer
    Join Date
    Feb 2021
    Posts
    8

    Position tolerance exercises

    Hello,

    I'm solving some question about position tolerance from a book and there are two of them which I didn't understand what is wrong with my resolution. Could someone help me with it?

    Picture for question 47 and 48:

    Capture.PNG

    47. For the feature control frame marked A, how much datum feature shift is allowed if the datum feature is produced at 14.8 and has 0.5 perpendicularity error?
    A. 0
    B. 0.4 (official answer)
    C. 0.5
    D. 0.9
    E. 1
    F. 1.2

    My resolution:

    Datum feature shift= MMB - rAME

    MMB= MMC + Geo tol. (respecting datum precedence) = 15.2 - 0 (No geo. tol. is added since datum B (MMC) is primary datum and perpendicularity tolerance applied to B depends on A) = 15.2

    rAME = uAME + perpendicularity error = 14.8 + 0.5 = 15.3

    Datum feature shift= 15.2 - 15.3 = -0.1 (This value tells me that there is a inteference of 0.1 which is the opposite of datum shift porpuse)

    -----------------------------------------------------------------------------------------------------------------------------------

    48. For the feature control frame marked A, how much datum feature shift is allowed if the datum feature is produced at 15.2 and has zero perpendicularity error?
    A. 0
    B. 0.4
    C. 0.5 (official awnser)
    D. 0.9
    E. 1
    F. 1.2

    My resolution:

    Datum feature shift= MMB - rAME

    MMB= MMC + Geo tol. (respecting datum precedence) = 15.2 - 0 (No geo. tol. is added since datum B (MMC) is primary datum and perpendicularity tolerance applied to B depends on A) = 15.2

    rAME = uAME + perpendicularity error = 15.2 + 0.5 = 15.2

    Datum feature shift= 15.2 - 15.2 = 0

    -----------------------------------------------------------------------------------------------------------------------------------

    In fact, both question seems to add the perpendicularity tolerance to MMB but isn't it breaking the datum precedence?

    PS: I'm studying GD&T by myself trough the standard and some books. So I don't have any teacher guiding me who could solve the exercises.
    Last edited by ivanginato; 06-18-2022 at 08:13 PM.

  2. #2
    Principle Engineer Cragyon's Avatar
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    Feb 2013
    Location
    Newark, NJ
    Posts
    291
    Who's book is this from?

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