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Andy Dingley Andy Dingley is offline
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Default bolts rusted in to cast iron bench

On 16 May, 09:29, Burlington Bertie
wrote:
I've got two park benches which I bought from Sheffield Council 20
years ago. These consist of cast iron ends coach bolted to wooden
planks. I had to replace the wood and the bolts and now it needs doing
again. This time most of the bolts wont budge and are rusted in solid.


The usual suspects:

Angle-grinder the nuts / heads off. If these are coach bolts, then
destroying the nut should allow them to punch out quite easily. Maybe
you need to grinder/gorillate the heads off too out of the wood, then
worry about tidying up the stumps in the CI later, when you're got
access.

Nut splitter. If you can't take a gruinder to the head, use a much
smaller screw-in wedge (Halfords etc) to split the nut.

Heat. A dull-red heat on the bolts will shift a lot of rust. Let them
cool before trying to undo them though. Often you use a grinder for
phase #1 (heads and wood) then heat for phase #2 (bolt stubs out of
the iron).

Electrolysis. Electrolytic de-rusting takes a few days but it de-rusts
CI beautifully and it can also often free up rusted bolts. It's
certainly the best way to prepare for re-painting - much better than
abrasives.

I doubt if any sort of Plus-gas / old brake fluid will work too well
on cast iron. WD-40 certainly won't.

Destroy something with extreme prejudice. Concentrate on what you nedd
(the iron) and what you don't (bolts / wood). Then be extremely brutal
to what you can afford to lose (plasma cutter) so long as it doesn't
hurt the piece you need to save. Lump hammers aren't picky enough for
this.

Applying a heavy hammer has resulted in me breaking a section off one
of the castings.


Don't use a lump hammer around cast iron. If you do, make sure that
the iron is well-supported. It needs to be supported directly beneath,
so that tehre's no bending. A block of soft timber with a hole in it
is helpful, but even then it's risky.