I went through three different collet adapters that said they were for 1/2 to 1/8 but none of them even tightened the bit. I think I ended up manually modifying the adapter so it could tighten more. I’d recommend an 1/8 bit with a 1/4 shank if possible. I don’t remember where I got the one that ended up working - sorry, that’s probably not much help.