Drilling tool fishing is probably every driller’s least favorite activity. But it happens. There are a huge number of tools available to fish almost anything out of the hole. For drill pipe and collars, there are overshots and spears — in many sizes for almost any job. But, when it comes to loose junk on the bottom of the hole, things get a little more interesting. It might be a loose bit, a wrench, a sledge hammer or tong dies. Anything that can fit in the hole will sooner or later end up on the bottom. I reckon it’s human nature, or Murphy’s law, but it happens.
Most commercial fishing tool companies have pretty sophisticated tools, such as reverse circulation junk baskets, and all kinds of well-engineered tools to do the job. But, sometimes, they are not quite what a customer needs. If the fish is large in relation to the hole size, such as a bit, a reverse basket will not pick it up because of the wall thickness. Something else is needed. Or, if the hole is just not worth the expense of using a commercial fishing company, a driller may opt to build his own fishing tool for the job.