The old 'Fleet Managers' trick with a fleet of Fords with this kind of key back in the day was a small drop of Arraldite on the outside of the key over the chip end. It sets to a smooth finish so no snags and if the chip needs removal for any reason can be peeled off with a penknife. It's just enough to hold the chip in place.

BR Colin
Who used to be a Spanner Juggler