> As it was explained to me:
 >
 > Eons ago, as large pipe mills became flexible enough to produce various
 > sizes and wall thickness, the timing of what-to-make-when was outlined by
 > production "schedules" based on new orders, projected demand, etc.
 >
 > As the industry evolved and sizes became standard, the term "schedule"
 > morphed into meaning a standard wall thickness for a certain size pipe.
 >
 > We are still stuck with the term.....
 >
 > Steve Webre
 > Broussard, LA

      The part of this to remember is that increasing the wall thickness of
pipe makes the ID smaller. The Extra wall thickness must be added on the
inside because all pipe "Schedules" must still screw into the appropriate
fitting size. So the OD of pipe remains the same between various "Schedules."
The fittings get bigger on the OD between "Schedules" because the threaded ID
must remain the same for all "Schedules."

       This is the same as tubing is it not?  One inch 4130 by .035" is one
inch in diameter. One inch by .065" is still one inch OD, but the ID is
smaller.  The increased wall thickness is on the inside.  Same/Same.

Lynn E. Hanover

Jack Beale wrote:

Lynn,

    I believe that it's mostly semantics, attributable to the pricing structure the steel
companies employed.

    Pipe is sold by OD/schedule, which translates into wall thickness.  The ID is left to 'float'
as the schedule changes.

    Tubing, on the other hand was sold as ID/OD/wall, meaning that the customer can specify
exactly what he wants.  If the ID is critical, the customer can specify ID/wall and let the OD
float.  He can also specify all three (ID/OD/wall) to 'nail-down' all the parameters.

Jack Beale
jack.beale@att.net

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