API Round Thread Casing Coupling - Dimensions, Tolerances and Masses
Size Designation
Pipe
Outside Diameter
Coupling
Outside Diameter
Minimum Length Diameter of
Recess
Q
Width of
Bearing Face
b
Mass
Short
Long
Short Long
D (in) D (in) W (in) (in) (in) (in) (in) (lb) (lb)
4-1/2 4.500 5.000 6 1/4 7 4 19/32 5/32 7.98 9.16
5 5.000 5.563 6 1/2 7 3/4 5  3/32 3/16 10.27 12.68
5-1/2 5.500 6.050 6 3/4 8 5 19/32 1/8 11.54 14.15
6-5/8 6.625 7.390 7 1/4 8 3/4 6 23/32 1/4 20.11 25.01
7 7.000 7.875 7 1/4 9 7  3/32 3/16 18.49 23.87
7-5/8 7.625 8.500 7 1/2 9 1/4 7 25/32 7/32 27.11 34.46
8-5/8 8.625 9.625 7 3/4 10 8 25/32 1/4 35.79 47.77
9-5/8 9.625 10.625 7 3/4 10 1/2 9 25/32 1/4 39.75 56.11
10-3/4 10.750 11.750 8 - 10 29/32 1/4 45.81 -
11-3/4 11.750 12.750 8 - 11 29/32 1/4 49.91 -
13-3/8 13.375 14.375 8 - 13 17/32 7/32 56.57 -
Refer Figures 1 and 2
The size designation for the Coupling is the same as the size designation for the Pipe on which the Coupling is used.
For Couplings, Groups 1, 2 and 3, Tolerance on Outside Diameter W: ± 1 % but not greater than ± 1/8 in.
For Couplings, Group 4, Tolerance on Outside Diameter W: ± 1 % but not greater than + 1/8 in, -1/16 in.
Tolerance on Diameter of Recess, Q, for all Groups: + 0.031 in, -0.00 in.