Forged Flanges – Dimensional Tolerances

ANSI B16.5

The tolerances listed below are always observed in the flange production and are to be understood as maximum limits, since the manufacture, effected by modern and properly equipped machines, usually ranges between more narrow limits. Said tolerances, unless otherwise specified, and those approved by American Standard ANSI B16.5.

DIMENSIONS IN INCHES

THREADED, SOCKET-WELDING SLIP-ON, LAP JOINT
AND BLIND FLANGES
OUTSIDE DIAMETERWhen O.D. is 5” or less+0.09”, -0.03”
When O.D. is 6” and above+ 0.16”, -0.03”
INSIDE DIAMETERThreadedTo Standard Gauge Limits
Socket-welding Slip-on and Lap Joint Sizes 10” and smaller+0.03”, -0”
Sizes 12” to 18”+ 0.06”, -0”
Sizes 20” and above+0.12”, -0.06”
DIAMETER OF
COUNTERBORE
Threaded Sizes 10” and below+0.03”, -0”
Threaded Sizes 12” and above+0.06”, -0”
Socket Weld  3” and below± 0.10”
DIAMETER OF CONTACT FACE1/16” Raised Face± 0.03”
¼” Raised Face Tongue and Groove or Male and Female± 0.02”
DRILLINGBolt Circle± 0.06”
Bolt Hole Spacing± 0.016”
Concentricity of Bolt Circle and Facing 2 ½” and below0.03”
Concentricity of Bolt Circle and Facing 3” and above0.06”
LENGTH THRU HUBSizes 18” and smaller+ 0.12”, -0.03”
Sizes 20” and larger+ 0.19”, -0.06”
THICKNESSSizes 18” and smaller+ 0.12”, -0”
Sizes 20” and larger+ 0.19”, -0”
WELDING NECK FLANGES
OUTSIDE DIAMETERWhen O.D. is 5” or less+0.09”, -0.03’
When O.D. is 6” and above+ 0.16”, -0.03”
INSIDE DIAMETERSizes 10” and smaller± 0.03”
Sizes 12” through 18”± 0.06”
Sizes 20” and larger+ 0.12”, -0.06”
DIAMETER OF CONTACT FACE1/16” Raised Face± 0.03”
¼” Raised Face± 0.02”
Tongue and Groove or Male and Female± 0.02”
DRILLINGBolt Circle± 0.06”
Bolt Hole Spacing± 0.03”
Concentricity of Bolt Circle and Facing 2½” and below0.03”
Concentricity of Bolt Circle and Facing 3” and above0.06”
LENGTH THRU HUBSizes 4” and smaller± 0.06”
Sizes 5” to 10”+0.06”, -0.12”
Sizes 12” and above+ 0.12”, -0.18”
THICKNESSSizes 12” and smaller+ 0.12”, -0”
Sizes 12” and larger+ 0.19”, -0”