Common defects of oil casing pipe thread:
1, Black top oil casing thread
2, Broken thread
3, Burr
4, Tremor
5, Marks
6, Scored thread
7, Dimples, indentations
8, Sub-standard thread height
9, Flash
10, Tear
11, Camfered insufficiency, bevel failed
12, Pitted thread
13, Casing deformity buckle
