If you encounter a stripped-out ski binding screw hole, you have several repair options.
You can mix up some epoxy and steel wool, and put it in the hole as you reinstall the screw...or you can redrill the hole with a 3.6mm drill bit, hammer in a wood plug, then redrill and reinstall the screw.
If neither of these approaches work, then try these plastic inserts.
You first drill out the screw hole using a 5/16" drill bit, then tap in one of these inserts before reinstalling the screw.
Cheap, fast and easy.
They don't have the holding power of helicoils, but are usually more than adequate if you only have one or two stripped screw holes per ski.