Drilling out sheared off bolts.

Buy suitable sized bolt extractors and use those. They look a bit like tapered screws with a coarse, reverse thread. You drill a hole into the centre of the bolt, screw in the bolt extractor and as it tightens up, it undoes the bolt. , assuming it isn't well corroded in place.

I last used these to remove the Philips-headed bolts from the allow crankcase of a Honda motorcycle gearbox - which meant being very careful!

8mm - the question was a general one, really, so I'm still interested in techniques!

Whatever the method of finally turning the stud, serious heat on the assembly is useful. The expansion helps to break the seal and/or soften whatever gunge is holding the threads together.

The message from Chris Bacon contains these words:

A friend and I once sheared off a head-bolt in his Morris 1100 A-series engine. we couldn't get it out so we drilled to a larger size and tapped for a bolt, wound it in with thread sealant then drilled and tapped that back to the original size. Worked fine, took an hour or so.

Hi,

I'd try tapping a normal (ie right hand) threaded hole in the stud then use a high tensile bolt and some Loctite threadlock of the "bloody well permanent" variety.

Some JB weld and an allen key or torx bit in a clear hole may work.

cheers, Pete.

I know some people tap in a torx or spline bit instead of a proper stud extractor, seems to work ok.

mrcheerful

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Bought a set of these a couple of years ago. They haven't let me down yet, work fine.

John

I assume this means a screw extractor. Yes, used them successfully many times. As long as the stump is not hardened you have the right size of extractor, not that it's critical. Most recently about a month ago, with a 2.6mm screw stuck in a TV camera front frame.

It's quite difficult if the break is angled and not reachable with a file, it's difficult to drill near the centre. Much easier with a stripped Philips screw head, the drill self-centres.

I'd try very hard to mount the drill and work solidly, you do need to go through somewhere near the centre, and that's very hard to do with a wobbly drill.

The old temperature cycling and a drop of Plus-Gas will help. Squirt some freezer down the hole just before you try moving it.

At that size, I would go for the way mrcheerful states. I did this, using a torx bit, on a car steering lock break off bolt and it worked a dream.

A poor mans timesert , beats helicoils.

FOr tiny screws/bolts the snappy xout type screw extracors work well

Or just buy a stud extractor, which is essentially the same thing...a reverse threaded self tapping screw that takes a wrench on its head...

Heat and WD40 or equivalent often breaks the corrosion.

Yes you can use this tool just the same BUT the tap and die comes in handy at some time or other for creating a left handed thread, whereas the stud extractor might never get used again. :-)

-- Sir Benjamin Middlethwaite