a Marking is convenient for getting information, and help to category control.
b Drill Collar No. is formed by two parts with hyphen--. The first part is NC --; the second part is formed with two numbers (or three numbers), using the integer and fraction of Inch to show the OD. For the drill collar with OD of 209.6mm、241.3mm and 279.4mm, as there is no NC connection within the range of recommended BSR, 6 5/8、7 5/8 and 8 5/8 REG connections are adopted.
c Tolerance: See Table 15
d Non-magnetic Drill Collar Tolerance: See Table 8.3.1.1
e In the calculation of BSR, the stress relief recess is not considered.
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