Tricks to remove rusted bolts from forestay fitting

[davidmh]

I am looking for ideas to remove a stubborn corroded bolt. The bolt is one of 10 holding part of the forestay plate on the GRP hull. The remaining 9 are all OK this one had a very rusty nut and when I tried to check the tightness it just sheared off under the nut level with the penny washer.

The Bolt, a c/sink setscrew really, is 8mm dia and goes through the stainless steel fabrication which is part of the forestay fitting, the fitted also goes down the outside of the stem and is through bolted with more bolts which all look good. They all seem to be stainless and the head of the faulty one has no corrosion visible.

Access from below deck is just possible, head and shoulders through the access hatch of the chain locker,

So far I have tried to drift it out from the underside but it is rock solid, I have tried to move the head from the outside with a chisel in the screwdriver slot but it does not move. I have left it soaked with penitrating oil in the hope that something will ease up.

My ideas now are - weld a nut onto the head of the screw and try to turn it to break the corrosion
Apply some heat but where and how.
Get it drilled out from the head side, access is Ok from above.

I don't think the fitting will fail any time soon, but If I can get it out I would like too.

Any suggestions welcome

Regards

David MH

 

[jiris]

There are electric tools that use high voltage sparks to virtually pulverise the material. I never used one, but they apparently work well.

 

[explores]

There are electric tools that use high voltage sparks to virtually pulverise the material. I never used one, but they apparently work well.

Spark eroders?

 

[jiris]

Yes, That's what I mean. They are often used by motor mechanics to remove broken head bolts from engine blocks.

 

[lw395]

Assume it's a slotted countersunk?
I would try a bit from an impact driver set. That might fit the slot properly and offer a 1/2inch drive adaptor to get some torque on it.
You could try a cordless impact driver, I would not use the hammer sort on my boat.
You may have to drill it out?
I would suspect that the reason it doesn't want to move might be it's got a big shear force on it?
So maybe re-tighten some of the other screws before attacking it?