| 摘要 |
A reversible casing (9) for a down-the-hole drill has a predetermined snap ring (50) groove length centered between the casing ends (11, 15), based upon the casing bore (42), the snap ring groove depth and th e snap ring body length, whereby a snap ring (50) will be retained in the snap ring groove (72), while permitting lengthwise movement of the snap ring (50) during reverse orientation of the casing (19).
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