Thankyou Ronald, for this tip! :D [color=#BFBFBF]Actually I had bought a WD-40 "pen" some time ago (for squeaky hinges on doors).[/color] I believe it worked - as I got that bolt out, finally!
The bolt itself looks heavily 'abused' by now (because of the brute force applied :twisted:), so I'll get a replacement later on.
But I can open the crank case, to fix my A-bike. :mrgreen:

Try soaking it in acetone, or just apply a few drops and let it stand. You can find it in hardware stores or just buy a small container of nail polish remover, which is basically just acetone. You can also try WD-40 or similar products. The purpose of the acetone is to dissolve the "lock nut" compound the factory used to make sure the bolts stay tight.

The bolt on top of the crank case, connecting to the Crosspiece bar, is too tight. This means I cannot open up the case for repairs/maintenance :shock: [img]http://api.ning.com/files/-9uTfRZAG3tUAwokDJQB*c*IMZmLGZ52bsLo29cLQlD9-RNdcWwNs1nXJzxsSLOxnu7iOtsqDwW7qHUUr6sFJgaJ*PVcK4Wp/abikerearhexbolt.jpg?width=150[/img][quote]Even when I apply great strength, it is useless: does not move a bit. To apply this much force only results in breaking the hexagonal 'hole' in the bolt, thus losing grip with the hexagonal wrench.
For a "second opinion", I've taken the A-bike to a 'regular' bicycle shop. They tried it with both a hexagonal wrench and a regular wrench/spanner, but with no result.
Now I don't know what to do... :-( Any ideas?[/quote][b]Update:[/b] finally I managed to get it to turn, with a 'Mole' wrench ([url=http://en.wikipedia.org/wiki/Mole_grip]Locking pliers[/url]) and now rather sore hands :shock:
But the nut/ring rotates with it. And it still won't come out. So there's yet another challenge for me to overcome...