A 20mm or 13/16 drill bit will allow the bolt to fit through.
10mm
10mm
10mm.. not 12mm
You drill the proper size hole in to the bolt and remove it with an E-Z Out.
10 mm would be ideal. But 13/32" will work.
8mm-10mm typically
10mm
remove alternator and bracket.with a drill bit smaller in size than he the thread on the broken bolt, carefully drill broken part of bolt that is still in engine.then use an" easy out " to remove broken peice.an" easy out" can be purchased with the correct size drill bit if you know the bolt size.
For a clearance hole you need a 9/64 drill bit.
YES, You must either drill it out and retap it to the next bolt size up are drill it out and install a heliecoil in it.
10mm 12 point