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  1. Apr 25, 2012 #1
    What does the thread note 3/8'' - 24UNF 2B x 1-1/2'' mean? I know that the diameter of the thread is 3/8'', but what's the 1-1/2''? Is that the length of the thread?
  2. jcsd
  3. Apr 25, 2012 #2


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    If this is a bolt, the 1-1/2" is the length from under the head to the tip of the bolt. It includes the shank. If this is a thread call out on a drawing, it means the thread is 1-1/2" long. You need to specify where you're seeing this call out.
  4. Apr 25, 2012 #3
    24UNF means 24 threads per inch. UNF means fine (as opposed to coarse UNC or extra-fine UNEF.

    "2B" is the tolerance of the internal threads. B means internal (A is external). 2 means medium tolerance. 1 is loose tolerance. 3 is close tolerance.

    Info from wikipedia:
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