I used $50-$100 bits. However, in the past my needs for this project have been modest, so I ordered this 4-bit kit for less than $30. I don't expect the durability to be that high, but the drills cut very cleanly and very quickly (in oak) and after more than 6 meters of cut they are cutting as well as when they started. In production, other bits may be preferred (plus 1/2" shank), but for the hobbyist, they turned out to be much better than expected.