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how to remove a bolt thats lost its head in a tight space? Answered

ok so i have a motorbike and on removing the exhaust at the manifold one of the bolts head came away without the bolt so i have about 1/2 cm to work with but not alot off space around



could you cut a line in the bolt with a dremel then use a flat head screwdriver in the slot

I checked with my friend: He said he had an engine where someone had drilled the bolt-out (oversize) and tapped it, quote: "real botch-job". He also confirmed something else, tapped aluminum blocks usually have a steel spiral insert (a bit like a spring) otherwise the threads tend to strip. L

Oh dear, this is a pain when it happens. I assume you sheared it off trying to get it out? caitlinsdad has given you most of the best suggestions, but I'd favour something different.
If the bolt-head sheared, I'm not convinced any extraction technique will move it. The bolt will be hard steel and the block will be soft aluminium alloy? Trying to drill that out and re-tap would be rather difficult, and your new bolt would be too big for the exhaust coupling.
I'd suggest drilling and tapping the bolt and screwing a smaller one into that. I believe one of my friends did just this, but I can't check right now.


You might want to try one of those screw-out or nut remover extractor type bits. One kind is where you have to drill a small hole in the center of the bolt/screw and place in the extractor bit. Reverse thread/ribs that grip when you back it out. If the head came off, a nut extractor won't be able to get any grip over the head and the confined space won't let you use vise-grips or a needle nose vise-grips. Whatever you try, use penetrating oil too loosen up the threads and use the extractor bits with an impact driver if you have one. Tricky way is to cut a screwdriver slot in the bolt with a dremel if it can fit. Otherwise worst case, you might have to drill through and retap the hole for a larger size bolt. Good luck.