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Thread: Roughness Rt Rzmax

  1. #1
    Associate Engineer
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    Oct 2015
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    Roughness Rt Rzmax

    Good morning everyone,

    First time I post on this forum, I hope section is right and question is good

    I've to dimension surface roughness and I've just got this reccomandation from supplier:
    (Rt n, Rzmax 2.5n)

    My point is: since Rt is maximum peak-valley height in evaluation length, it should be greater or equal then Rzmax (calculate on sampling length). Also assuming 16% rule for Rt, Rzmax should be at most 1.16n.

    Are there other points to be considered in comparing these two roughness parameters?

    Thanks for supporting,

  2. #2
    Administrator Kelly Bramble's Avatar
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    Quote Originally Posted by cammarasana123 View Post
    I've to dimension surface roughness and I've just got this reccomandation from supplier:
    (Rt n, Rzmax 2.5n)

    My point is: since Rt is maximum peak-valley height in evaluation length, it should be greater or equal then Rzmax (calculate on sampling length). Also assuming 16% rule for Rt, Rzmax should be at most 1.16n.
    Yes, assuming ISO 4287 - Rt is the Total height of the roughness profile (peak to peak) and Rz is the maximum height of the roughness profile from the mean.

    I suspect that your supplier simply got Rt and Rz reversed..

    Going forward - the surface roughness requirements should be specified first by functional requirements and secondly if the functional requirements are not critical then specified by the target manufacturing process (economics does matter)..

    For reference, see:

    Surface Roughness Conversion
    Last edited by Kelly Bramble; 10-06-2015 at 07:51 AM.
    Tell me and I forget. Teach me and I remember. Involve me and I learn.

  3. #3
    Associate Engineer
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    Oct 2015
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    Re

    Quote Originally Posted by Kelly Bramble View Post
    Yes, assuming ISO 4287 - Rt is the Total height of the roughness profile (peak to peak) and Rz is the maximum height of the roughness profile from the mean.

    I suspect that your supplier simply got Rt and Rz reversed..

    Going forward - the surface roughness requirements should be specified first by functional requirements and secondly if the functional requirements are not critical then specified by the target manufacturing process (economics does matter)..

    For reference, see:

    Surface Roughness Conversion
    Hi,

    many thanks for supporting !!

    Simone

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