How to replace Kenwood chef KM400 small nylon spindle?

A mother-in-law wore out the black spindle surround probably after inserting the mincer blade backwards. I have a new plastic spindle but the old one is held in place by two bits of metal, horizontal to the metal spindle, that fit into two holes in the plastic spindle. How to remove other than with a hacksaw and then how to replace as the plastic feels very solid and inflexible (eg in case of a hammer blow).