While restoring an old carburetor I found out that a couple of the bolt holes were stripped, the fix for this is a Heli-Coil kit.  The kits include a drill bit, tap, coils and an installer tool.  The basic steps are outlined below.

Here is a coil threaded on to a stud before installation, as you can see the 5/16-18 coil fits perfectly.
Next drill and tap the stripped hole using the drill bit and tap supplied in the kit. Tip: Using a cutting oil or other light lubricant will make it easier to thread the new hole.
Put the coil on the installer tool included in the kit, notice the tang going into the notch.
Carefully thread the coil into the hole that you just tapped.
The finished product is shown to the right.