I have a set of standard length (6") Bosch DareDevil spade bits and need them to drill a hole in wood posts about 6" in diameter . Corner of the room for new wiring, just a little deep for standard length. I got this extension despite some pretty negative reviews. It worked great. It held up despite the heavy drilling and I had to use a percussion tool instead of a drill to finish the hole. The set screws are not what I want, but they work and you don't have to tighten them unnecessarily. Theβ¦