A bolt snapped off in a threaded hole happens in garages and on building sites alike. The most reliable way to get it out without welding is a bolt extractor. Here is how to do it and how to make the job easier.
What you need
Tip: before you start, soak the broken stud with
WD-40 Specialist Penetrant and wait 10-15 minutes. It works into the thread, dissolves rust and the piece comes out much easier.
Step 1
Mark the centre
Place a centre punch or a sharp nail exactly in the middle of the broken bolt and tap it with a hammer. The mark stops the drill from wandering and damaging the hole thread.
Step 2
Drill a pilot hole
Drill on the mark with a left-hand bit with the drill in reverse. Quite often the bit grabs the stud and unscrews it at this stage, then you can pull it out with pliers.
Step 3
Insert the extractor
Choose an extractor that matches the hole. It is tapered with a left-hand thread. Tap it in lightly with a hammer so it seats firmly, then fit a tap wrench or socket.
Step 4
Unscrew the stud
Turn the extractor anticlockwise. The taper locks in the hole and transfers torque to the bolt. Turn steadily without jerking until the stud is out. If it is tight, apply penetrant to the thread again.
Step 5
Clean the thread
Remove metal swarf with a magnet or compressed air, run a tap through the thread if needed and fit a new bolt. To stop it seizing in future, treat the thread with WD-40 Multi-Use Product.
Conclusion
An extractor is for when the bolt has already broken. To avoid that, treat rusted joints with WD-40 Specialist Fast Release Penetrant before undoing them: it penetrates the thread quickly and reduces the risk of snapping the bolt.