I got given this board and one screw in the turtle box is rusted and just wont come out. I have broken about 4 screw drivers and used heaps of wd - 40. I was thinking about drilling the head of the screw off. When i take out the other screw, the fin is wobbly so the fin isn't jammed.

Drill the head off it and pull it out from below.
I suggest drilling a narrow pilot hole first to ensure the bigger hole you drill remains centered.

Looks like from that 1st pic that there is still some groove for the screwdriver to engage in? And then the second pic is unclear.
If there is enough screw head groove remaining that you can at least apply some torque before it slips:

Use the right sized driver and quality :) put a wide elastic band over the screwdriver tip, then push down HARD and turn whilst somebody taps the screwdriver handle down with a hammer - like about half as hard as you'd hit to drive a nail into pine. The shock loading alone can often be enough. If the head is stuffed bad enough nothing will work and drilling will be ur only option, just thought I'd mention the above as a last ditch effort.

Drill a small hole and use an "easyout". You can get one from local hardware....left hand tapered thread. should do the trick if no luck with hammer and screwdriver.

find who used a mild steel screw instead of stainless and .... { insert punishment }

We used to use hammer and chisel, bang the side of the head until it turned, less technically refined, but good for anger management.

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Mark _australia said...

Use the right sized driver and quality :) put a wide elastic band over the screwdriver tip, then push down HARD and turn whilst somebody taps the screwdriver handle down with a hammer - like about half as hard as you'd hit to drive a nail into pine. The shock loading alone can often be enough. If the head is stuffed bad enough nothing will work and drilling will be ur only option, just thought I'd mention the above as a last ditch effort.

+1

Also try not only loosening, but tightening as well. If you manage to get it to turn even a tiny bit back and forth then it should loosen itself fully with enough persistence.

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Fez said...
Drill a small hole and use an "easyout". You can get one from local hardware....left hand tapered thread. should do the trick if no luck with hammer and screwdriver.

Instead of an easyout I have found a lefthanded drill bit works much better, about the same diameter as the bolt. When it catches it will grab and unscrew the bolt. The problem with the easyout is first trying to drill a tiny hole then inserting the tiny screw extractor and trying to grab hold of it to turn it and perhaps having it snap off in the hole, then you are really screwed
This worked so much better for removing broken starter bolts from an engine block.

try soaking in deisel for a few days

What about a die grinder that should cut the head of it!

being in a hole about 75mm deep makes grinding / cutting / easyouts a bit hard.....

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Mark _australia said...
Looks like from that 1st pic that there is still some groove for the screwdriver to engage in? And then the second pic is unclear.
If there is enough screw head groove remaining that you can at least apply some torque before it slips:

Use the right sized driver and quality :) put a wide elastic band over the screwdriver tip, then push down HARD and turn whilst somebody taps the screwdriver handle down with a hammer - like about half as hard as you'd hit to drive a nail into pine. The shock loading alone can often be enough. If the head is stuffed bad enough nothing will work and drilling will be ur only option, just thought I'd mention the above as a last ditch effort.

Put the blade of the fin in a vice below the board when you hit it from above, (pack to the shoulders of the fin base so it doesn't slip in the jaws). Otherwise the fin box will just flex. So how does the elastic band help? Heat can help but you'd probably melt the fin box before it conducted down to the rusty bit.

Rubber bands help fill in the gap a bit and increase friction. Does not always work, and neither does the shock from hammering. Put all together with a quality driver and it is a last ditch effort that may work.

I find impact drivers work pretty well, they are essentially designed for just this situation.