4mm screwdriver bit to 6.3mm adapter with magnet

thingiverse

As the pictures show, I insert a magnet, Φ5 * 1.7mm, into the middle position to hold the 4mm bit. And a M2 screw to let a 6.3mm screwdriver catch the adapter. The notch significantly makes it more fragile. I think it can endure no more than 1N.m torque, still useable, though. The contact area with bed is small, so raft may be needed.