Table C.7—Critical Thickness for Couplings with  API Threads
Label 1Critical Thickness for Couplings
Special Clearance
NUEUEUBCBCLCSC
12345678
1.054.295.36
1.3155.366.55
1.666.076.1
1.94.986.38
2 3/87.727.625.69
2 7/89.659.096.45
3 1/211.4611.537.47
411.5311.63
4 1/211.0512.526.5811.3512.0411.74
56.7612.1712.9812.47
5 1/26.8112.2813.0612.57
6 5/86.9611.9112.912.32
77.1113.4614.4313.72
7 5/88.8413.6114.5513.87
8 5/88.9415.2916.4315.54
9 5/88.9415.2916.6915.6
10 3/48.9415.2915.7
11 3/415.2915.7
13 3/815.2915.7
1616.9416.05
18 5/821.6920.8
2016.9417.0916.1
NOTE The coupling blank thickness is greater than those indicated above, due to thread height and manufacturing allowance to avoid black crest threads.

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