Any ideas how to remove this difficult bolt.

Concerto

Concerto

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Water tank bolt 1000pix.jpg

I am having to remove my water tank to get a small leak repaired. On my Westerly Fulmar it islocated under the cockpit and was fitted before the deck was fixed. The tank is fixed down with 4 bolts. I have removed 3 of them. The 4th is shown by the blue arrow. It can only be accessed via a small hole and is about 24" away. My initial thoughts are to either drill around the bolt so I can break it out or to take my multitool with a saw blade and cut a slot in the plywood to push the tank aft to release the bolt. It might be possible to use the multitool to cut the head off the bolt with a metal cutting blade, but it is a 4mm and will be difficult There is no way to reach the bolt without cutting into another bulkhead in the quarter berth, which I am very reluctant to do. Any other ides?
 
Because you said it was a "difficult" bolt I assume you've tried undoing it with a small 6mm drive socket (if it's hex head) and it won't release.
I've just blown your photo up and it looks more like a screw with posi-drive or phillips head. Again I make an assumption that you've tried with a crosshead bit in a small socket handle and it won't come out.
I've never had any luck cutting stainless screws/ bolts with a multi tool because the blades go blunt so quickly. Maybe if you get really good quality blades you might get it that way but they're not cheap.
You could try cutting the slot to let it move backwards but you can't complete the cut out fully and you may finish up damaging the ply base more than you think.
If there were other things in the area that needed access then I'd be tempted to cut the bulkhead neatly with the multitool and make a neat hatch, But it looks like there's nothing else there worth accessing.
What would I do?
Buy the best stainless blade for the multitool you can and try that first. Easiest option.
Then I'd go for the slot in the base option, accept the damage (easily repaired once the tank is out of the way).
If that failed then the hatch in the bulkhead would be last option.
So no new ideas for you but maybe confirmation that your ideas make sense and there aren't any realistic alternatives given the difficult access.
 
The bolt is a pan head with a slot.
There is not enough room to get two arms in for a spanner and a screw driver.
The Fein multitool I have has metal cutting blades and I have several new ones, so I may try this first.
If I cut a slot in the plywood, I could have a bolt with a penny washer fitted that would just slip over the plywood when refitted to limit any upward movement on that corner.

The idea of using a powerfile is one I had not thought of. I do have one onboard, so worth a try. Must use some covering to catch the metal filings.
 
Concerto said:
The bolt is a pan head with a slot.
There is not enough room to get two arms in for a spanner and a screw driver.
The Fein multitool I have has metal cutting blades and I have several new ones, so I may try this first.
If I cut a slot in the plywood, I could have a bolt with a penny washer fitted that would just slip over the plywood when refitted to limit any upward movement on that corner.

The idea of using a powerfile is one I had not thought of. I do have one onboard, so worth a try. Must use some covering to catch the metal filings.
Click to expand...

Heavy duty hoovers are wonderful things!
 
Angle grinder, or a drwmmel with, probably, multiple discs as I've found they don't last long

You can get an extension for the dremmel, tape it to a stick to give you control at a distance.
 
There is very little to grip with mole grips and would be difficult at the distance fromthe opening to get good leverage.

An angle grinder might work to remove the head. A Dremel would use a lager number of cutting discs, and I would have to get some as I only have a few at the moment.

No room to hold an impact driver, let alone hold the nut.
 
I wouldn't muck about with angle grinder, Dremel etc. I would simply make an access panel in the bulkhead. This would also allow access to the offending screw and also to the fuel valve(?) on the left of your picture and the pipe work.
 
Cutting another access hole would not be difficult and covering a plywood cover with matching foam backed vinyl would be simple. This would be my last choice.

The valve on the diesel tank can be reached quite easily.
 
Small mole grips on the head. Ratchet spanner on the nut. Grips will turn with head untill they contact opposite side and so lock screw. Nut will then unfasten ! Spanner length can be extended by taping a bit of wood to it so it's easier to reach though this reduces the available rotation. Even easier with right angle drill/ nut runner and socket instead of ratchet spanner.
 
Excuse the crappy sketch (I tend to think with my hands) but this might work. Put a bolt through the spare end of the spanner as sketched, and a washer fixed at the appropriate height so it hooks on the wood. This stops the spanner rotating. Fix the ensemble in place with a lump of putty or suchlike so the working end stays located. Now you only need to operate the screwdriver.
 

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oh, and replace the bolt with something you can put a ratchet on, and the nut with one of these, for next time

detail.jpg
 
If you can reach it, then why can you not just put a thin cutting disc in a 4 inch angle grinder & take the head off? You can hold an angle grinder in one hand easily enough & if you rotate the guard correctly you can use it to hold it against the tank so that the blade touches the screw & does not engage with the tank. If difficult to cut horizintally then cut vertically through the bracket & have a new one fitted when the leak is repaired. It could then go in a more accessible position - even if you do get this one off OK.
 
I had a couple of removable panels to access areas. ( one an awkward corner of transom and more importantly , tool sized access to steering gear at cockpit base from quarter berth) .
More work initially but you’ve done such a great job on the rest of the boat, you would be future proofing.
As Poignard points out, there is important plumbing stuff to access too !
 
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