Construction and fabrication tolerances for straightness ( Camber and sweep )of components made from standard steel sections often refer back to "Mill tolerances".
Today I am working on 18 plus internal drawings created between 1946 and 1995 that have notes that require our inspection department to confirm the steel "stock must be within rolling Mill tolerances set by the American steel industry." And of course I am working on these because a customer just rejected and returned an entire lot of parts made by a long time suppler because they are "bent."
Some reference documents, even from the most honorable and steadfast AISC, make seemingly iron clad statements like "Mill dimensional tolerances are completely set forth in ASTM A6/A6M. "
However a quick check of ASTM A6 took me to Table 21 "Permitted Variations in Straightness for S, M, C, MC, L, T, Z, and Bulb Angle Shapes."
"Oh boy!", I thought. We've got them now Robin/Watson/Tonto.
Then the legend for table 21 had this to say about "sweep" (sideways or Axis 2-2 bending).
"Due to the extreme variations in flexibility of these shapes, permitted variations for sweep are subject to negotiations between the manufacturer and the purchaser for the individual sections involved."
I guess I can see how our Design graphics group would perpetuate a note that has "worked" for decades.
I am about to replace the existing note with one that limits the "sweep" to the same value as the "camber" .
Does anyone see something I am overlooking ?
thanks,
Dan T
Today I am working on 18 plus internal drawings created between 1946 and 1995 that have notes that require our inspection department to confirm the steel "stock must be within rolling Mill tolerances set by the American steel industry." And of course I am working on these because a customer just rejected and returned an entire lot of parts made by a long time suppler because they are "bent."
Some reference documents, even from the most honorable and steadfast AISC, make seemingly iron clad statements like "Mill dimensional tolerances are completely set forth in ASTM A6/A6M. "
However a quick check of ASTM A6 took me to Table 21 "Permitted Variations in Straightness for S, M, C, MC, L, T, Z, and Bulb Angle Shapes."
"Oh boy!", I thought. We've got them now Robin/Watson/Tonto.
Then the legend for table 21 had this to say about "sweep" (sideways or Axis 2-2 bending).
"Due to the extreme variations in flexibility of these shapes, permitted variations for sweep are subject to negotiations between the manufacturer and the purchaser for the individual sections involved."
I guess I can see how our Design graphics group would perpetuate a note that has "worked" for decades.
I am about to replace the existing note with one that limits the "sweep" to the same value as the "camber" .
Does anyone see something I am overlooking ?
thanks,
Dan T