API Buttress Thread Casing Coupling - Dimensions, Tolerances and Masses
Size Designation
Pipe
Outside Diameter
Coupling Minimum Length
Diameter of
Counterbore
 Q
Width of
Bearing Face
b
Mass
Regular Special 
Clearance
Regular Special
Clearance
Outside Diameter
D (in) D (in) W (in) W (in) (in) (in) (in) (lb) (lb)
4-1/2 4.500 5.000 4.875 8  7/8 4.640 1/8 10.12 7.68
5 5.000 5.563 5.375 9  1/8 5.140 5/32 13.00 8.82
5-1/2 5.500 6.050 5.875 9  1/4 5.640 5/32 14.15 9.85
6-5/8 6.625 7.390 7.000 9  5/8 6.765 1/4 24.49 12.46
7 7.000 7.875 7.375 10 7.140 7/32 23.24 13.84
7-5/8 7.625 8.500 8.125 10  3/8 7.765 5/16 34.88 20.47
8-5/8 8.625 9.625 9.125 10  5/8 8.765 3/8 45.99 23.80
9-5/8 9.625 10.625 10.125 10  5/8 9.765 3/8 51.05 26.49
10-3/4 10.750 11.750 11.250 10  5/8 10.890 3/8 56.74 29.52
11-3/4 11.750 12.750 - 10  5/8 11.890 3/8 61.80 -
13-3/8 13.375 14.375 - 10  5/8 13.515 3/8 70.03 -
Refer Figure 3
The size designation for the Coupling is the same as the size designation for the Pipe on which the Coupling is used.
For Regular Couplings, Groups 1, 2 and 3, Tolerance on Outside Diameter W: ± 1 % but not greater than ± 1/8 in.
For Regular Couplings, Group 4, Tolerance on Outside Diameter W: ± 1 % but not greater than + 1/8 in, -1/16 in.
For Special Clearance Couplings, Groups 1, 2 and 3, Tolerance on Outside Diameter W: -1/64 in,  +1/32 in.