The usual way is to use a pair of mole grips to grip the bit
Then use a pair of water pump pliers to grip the chuck. If you wish you may wrap the chuck with tape or simply a piece of cloth to protect the plastic chuck if the pliers should slip
Rotate the chuck anti clockwise
That way you can normally release the chuck
Mole grips or similar - you need to really tighten those on the bit
Only to show you what I mean i case you do not know what mile grips or locking pliers are
Amazon.co.uk : mole grips
Water pump pliers
Amazon.co.uk : water pump pliers
Then use a pair of water pump pliers to grip the chuck. If you wish you may wrap the chuck with tape or simply a piece of cloth to protect the plastic chuck if the pliers should slip
Rotate the chuck anti clockwise
That way you can normally release the chuck
Mole grips or similar - you need to really tighten those on the bit
Only to show you what I mean i case you do not know what mile grips or locking pliers are
Amazon.co.uk : mole grips
Water pump pliers
Amazon.co.uk : water pump pliers