remove frozen, broken bolts

Ross · Feb 2, 2009

You checked with a magnet? Sometimes a pin punch and a hammer on the bolt stubs will help to loosen the rust. Tapping the plate left and right and fore and aft with a block of hard wood and a hammer might help. A thin prybar applied carefully. Don't expect anything to work instantly but just keep worrying it and it should work loose.

Maine Sail · Feb 2, 2009

John

That plate, if like my old C-36, should be cast aluminum. Unfortunately the screws or bolts that hold them to the mast base are stainless and aluminum and stainless do not like each other. If you find something to break the bond (read virtual welding) between corroded stainless and aluminum please let the rest of use know.

I've even tried acid to eat the corrosion but still have not had much luck. I've never found PB or any good quality penetrating oil to break the bond between corroded stainless & aluminum.

The best tool that I have found for dealing with this is an impact wrench..

Keep working at it and good luck!!

rockp2 · Feb 2, 2009

John said:
So today I had the (keel stepped) mast pulled on my C36. This was in preparation for removing the bulkhead. One problem I ran into: The plate that the mast sits on is made of cast iron (I think). Anyway, there are four bolts holding this plate down. These screws have corroded so badly that they all broke off when I tried to unscrew them. What's worse is that they seem to be frozen, bonded, to the plate itself inside the holes. At least I think that's the problem In any case, I can't pry this plate up off of them. (I'm assuming that the plate isn't fixed to the boat in some what that I can't see.)

I've sprayed PB Blaster onto them and I'm hoping that after it works its way down that this will loosen up, but if it doesn't, what suggestions do you have? Should I try heating the plate up? If so, use a heat gun or a propane torch? Any other suggestions?

Thanks.

(NOTE: This plate sits up high enough that I can't get the new bulkhead in. I just cut some off the bottom of the old one to slide it out, but obviously I don't want to be doing that with the new one.)

John,
First I want to say that my knowledge of boats wouldn't fill a thimble compared to most on this site. But I can speak to rusted bolts from using heat on car and truck bolts previously.

However, if you can use heat and not damage any fiberglass or anything, you would want to use a propane torch. Remember, I cannot tell you if that heat would damage your boat or not. I DO NOT have that knowledge.

The heat gun would not get things hot enough to break the bolts free. Also, there has to be something for you to use to turn the bolts. Like an EZ-Out (or another brand name) that you can get at any Lowes or Home Depot. Just make sure you get the size you need. Acutally I would try the EZ-Out prior to using the heat to see if that works by itself first. You'd be surprised how well they work. You also have to get the right sized drill bit to make the hole into the bolt for the EZ-Out.

sailaway78 · Feb 2, 2009

You first need to learn what they are

I suspect that as usual, Mainesail is correct in stating that the bolts are stainless. If so you are going to have to work at it. If they are not, I would recommend just rigging yourself up a little jig, and drill them out, then re tap to one size bigger. The cast iron keel will be easy to drill and tap. If they are a decent quality stainless drilling could be an option, but would not be an easy one.

rockp2 · Feb 3, 2009

Threads?

If the bolts are not threaded to the plate or any other fixed location, and are only threaded into a nut, try an air chisel. There is a bit attachement that may fit into the hole enough to break the bolt free.

If plate or other fixed location is threaded, I would still try any EZ-Out.

kloudie1 · Feb 3, 2009

That is a mess, John.. Heat might help since you'll have a net clearance growth of a teeny amount because aluminum (if that is what the base is) expands more than stainless does. (300F gives you a net opening of about 1.5 ten thousandths, assuming a 1/4" bolt) Chilling with ice and heating the edge of the base by the hole will maximize the movement between the bolt and the hole. Try to heat the base very quickly and locally with a torch to maximize movement.. and bang it and pry it before the bolts get as hot as the base. I know a heat gun can get really hot, but the heat gun will more evenly heat the base and bolts and the motion will be minimized. I don't know the configuration so there may be a real danger of damaging the fiberglass around (under?) the mast base. Pouring on the penetrating oil and worrying the base with a hammer and protection block and a pry bar, as Ross said, probably has the highest probability of success.. but it may take a while.. a few days.. Most penetrating oils are flamable so it will burn when ya address it with a torch.

kloudie1 · Feb 3, 2009

Ohhhh Wood screws probably means they are screwed into the fiberglass.. Nix the torch idea.. probably would damage the glass ..

caguy · Feb 3, 2009

What size bolts are you talking about? You might get them to move with a small gear puller. Once rigged up tap the top of the gear puller. If the plate is being held by am adhesive on the bottom this may loosen that too.
A picture would be helpful, for that see Ross' posting on things that can be done with a digital camera.

Benny · Feb 3, 2009

John I would try to drill through the screws and then use a pry bar to detach the plate from the base. Those corroded screws should not be hard to drill enough to weaken them so the the pry bar can do its job.

Mike Holibar · Feb 12, 2009

John, I wonder if the casting is set in some sort of bedding compound? Some heat from a heat gun, taking it gently, may soften the compound and allow you to lever the casting loose. I would guess that the ss screws were seized in the aluminium but will not be seized in the glass so it would be useful to leave stubs protruding once the casting is off. Then the screws will come out using vice grips. A few judicious taps with a hammer and cold chisel at the joint between casting and glass adjacent to the screw may just be enough to crack the corrosion away from the screw. The problem is it takes a bit of experience to know just how hard you can tap something before risking damage!! Regards, Mike.

Ron20324 · Feb 12, 2009

There's always the friendly Dremel tool with a cutting disc to cut the heads off.

sailingdog · Feb 12, 2009

One warning with heating aluminum. If it is heat treated aluminum, which most spars are made of, heating it with a torch will remove the tempering that gives the aluminum a majority of its strength. DO NOT HEAT ALUMINUM SPARS with a torch if you can avoid it.

Prime Time · Feb 12, 2009

Have you considered calling Catalina? I'm sure you are not the first with this problem.