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Why don’t they just retract the bits and change them like I would on a regular drill that needs a new bit? Is the failure mode they always or often fall off th
by ada1981 2y ago
Why don’t they just retract the bits and change them like I would on a regular drill that needs a new bit?
Is the failure mode they always or often fall off the shank into the hole and they can’t be extracted?
- ufmace 2y agoThat's exactly what they do. It just takes a while since there's tens of thousands of feet of drillstring.
- ada1981 2y agoThen what’s the jive about needing to drill around the old bits?
- Retric 2y agoRemoving many miles of pipe to swap out a drill bit at the end is slow and seems rather inefficient. Which suggests just leaving the old drill bit somewhere in the ground. But currently doing that would also involve removing the pipe, as to why: https://news.ycombinator.com/item?id=43371776 https://news.ycombinator.com/item?id=43371776
- ufmace 2y agoThat was answering silly speculation about intentionally leaving worn-out drill bits behind. There are actually workable procedures for drilling around things, but it's far more cumbersome and time-consuming than replacing a bit normally. Those procedures used for things like the drillstring getting stuck due to hole collapse; nobody would do that just for a worn-out drill bit. The actual way to avoid the problem is by using bits whose design lifetime in the formation you're drilling is at least as long as the hole section you're planning to drill.