My friend needs to replace his front caliper brakes on his old (80s) Schwinn road bike. Well he bought a basic front caliper brake, but the problem is the part where he bolts it onto the fork isn't long enough to screw on! What can be done about that?
It sounds like your friend has an older-fashioned fork that is not drilled for a modern recessed-allen mount. Most sidepull brakes sold these days have the recessed mounting hardware. Sheldon Brown (as usual) has an excellent explanation of what's going on and what you can do about it: