Worked really well at first until I must have hit a rock or big root. The hex shank is bent, I tried to straighten it but too much loosens it even more. I think the shank tapers outwards near the coil, so the chuck needs to be open about 1/4" to hold the bit in the bit. I bought this for a 4" bit. I can't wait for this to last much longer. I have to buy another one now as I still have 2/3 of my work. I have to say I ranged from very excited to very disappointed.