Brake disc screw sheared off

The cross head screw on one of my brake discs has sheared, with the threaded part stuck in the hub (not me - bought it like that!!). How safety critical is that, given that the wheel studs appear to hold everything together? In other words should I fix this as a priority?

Its not safety critical at all, the only issue is when you remove/replace the wheel, it can be a hassle as the disc can spin on the hub and make replacing the wheel a game of cat and mouse. If you plan on drilling it out, start off with a sharp, decent quality bit and use drilling lube. If you start with a blunt one, you'll only serve to heat up the area and "work harden" the remains of the screw.

phew! Thanks for that

in the meantime if your concerned just get a wheel removal assist tool. Basically threaded bar, either plastic or metal, which will keep everything lined up when changing wheels.

Once you get the old one out or the disc off, you can redrill a new hole.

The easiest way to do this is to fit the disc, bolt it onto the hub using the wheel bolts and then drill through in one go this way you ensure everything is lined up just peachy.

Good advice with the sharp drill and cutting fluid as well. I use cobalt tipped drills for things like this, seem to make life a little easier.