With the propane, set it up so the flame runs across the bolt, parallel to the face plate...jig it up so you can light the torch and leave it for a good long time without having to hold it by hand, which wears your patience. You may have to flame it for 5 or 10 minutes. Try the vise grips and then the freeze off if the heat does not do it.

I am not so sure I would try immediately alternating between heating then freezing the bolt. Try one and if it does not work then try the other. Between the two, a pair of vice pliers and a mallet you will get it off. If you have multiple unsuccessful attempts then just drill it and re-tap the hole.

When using the vise pliers make sure that they are so tight on the bolt that you need to use everything you have strength wise to clamp them down. You need them incredibly tight to not slip. Make sure you then smack it with the mallet in the correct direction . Also, I can only speak to success when using the vice grips with the freezing penetrating oil (I am sure many can speak to success with both approaches). I only use the torch to try and break up the rust, I never follow the heat with grips / mallet due to expansion. With the heat from the torch you are softening the metal and with freezing it you are further hardening / strengthening the metal. The first will make the grips slip easier the second should make them grip a little better. Not to mention that metal expands with heat and contracts with freezing.

With all of that said, I think drilling / re-tapping the hole is the least frustrating .

Wow... I just skimmed over your project thus far and can see that you truly have,"Grabbed a bull by the horns!" But, "More power to you!"
The bolt that you are trying to get out... by the look of it from the inside (the long end of the bolt) already has the threading messed up and almost looks as if there is solder of some sort in near the plate... Not sure about that. You are not going to get that bolt out through the front with that threading on the inside messed up.
If I had that problem I would cut the bolt off flush with the outside and if I had enough clearance to the inside of the plate, I would attempt taking it out from the other direction. Get that plate into some sort of a vise that can hold it steady. I would cut it off flush with the outside. Get a drill bit (a tough one... cobalt or better) half the diameter of you bolt. But first try to dimple in the center of your bolt with a drill bit about on quarter the size of the bolt (it doesn't have to be deep, but enough so that the larger drill bit tip will be guided and not try to shear off to the side. Then drill to the depth that the bolt is into the wall but not through the depth of the wall. Then I would get a good penetrating oil such as PB penetrating oil and soak down both side overnight. When drilling the bolt don't get real aggressive and use a slower speed and tapping fluid to keep everything lubricated as you are drilling. Drill a little and then use the tapping fluid and then drill again. After you are done drilling use some more penetrating oil and let it sit for a while longer. Then try the heat from the outside of the plate and turn it in through to the inside. This is all assuming that you have the clearance to work from the other side.
When cutting the bolt off I would use the dremel with a cutting wheel and work it around the diameter of the bolt and then in to avoid flaring the bolt and theus making it even more difficult to extract.
Added comment: Just a couple other thoughts as an addendum: When you heated the bolt for so long you did do one other thing... you heat treated it... in other words you hardened it a bit and made it a bit more brittle.
If you go this course, after you have cut off the bolt, take your dremel wheel and run it across the face of the bolt at a perpendicular angle to make it a bit concave and then have a center punch handy to put a nice little dimple in the center of the bolt to get your smallest bit started in dead center position.
Also you could try all of this from the opposite direction but you need to ensure that you have the clearances to work with a drill to get a dead center angle through the bolt.
JMHO

Good to hear your perspective on this project.
Of course you could take this problem to the machine shop and insideof 2 hours they could take out all the bolts by cutting them off... finding center for each one... drilling them out and rethreading all of them. The total cost would be maybe $100.
But of course this is not why you took this project on. Look at it this way... Even if you are not successful in your valiant attempts, you are not going to screw it up so much that a good machinist can't fix it. So have at it and enjoy!

drgary wrote:Doug,

Since I don't have a bead blaster in my garage, I'm thinking of using the wire polishing attachment to my Dremel tool to clean off the rust that way. Do you think that's worth a try?

Doug and Ray,

I just applied some penetrating oil and will let it sit until I try and open the boiler and address the cut-off bolt head at that time. BTW, someone suggested a combination of heat and cold. Is it worth getting some freezing spray too and alternate between heat and cold to try and get some expansion followed by contraction to free things up?

A wire brush is probably all you need, as far as removing the rust. If you have a die grinder (or a drill will work also), then you might also try a 3M rust/paint stripping pad. They are a fiberlgass sort of rust/paint stripping wheel. Most auto body / paint supply places carry them. They are for quickly removing rust and stripping paint off cars. Should make short work of a lot of the rust you have on your machine. Here's what they look like:



http://www.amazon.com/3M-7772ES-Paint-R ... B002E9IQ9M

As far as the hot mixed with cold thing... if you are trying to slip a bearing on a shaft or something (and it has an interference fit or something), then yes, you can get into doing stuff like that. For example, you chill the shaft, then heat the bearing in the oven to maybe 400 or 500 degrees. Then you have a few seconds to slip the bearing on the shaft and the temperature differential will help you produce a better fit, etc.

However, in terms of unsticking a frozen nut or bolt, all you really need is heat. You don't need to get real fancy with chilling some parts and heating others. Also, if the parts are in contact, you aren't going to really be able to affect one and not the other.

We are talking more cave man stuff here... not installing protective tiles on the space shuttle or something like putting something into orbit around the earth. You should be thinking more along these lines:

"me heat you very very hot!!!"

"me grip you very hard!!!"

"me turn hard to left"

"you come off now!!!"

done...

Ray

Heat up the housing, not so much the bolt itself.

If you heat the bolt up to be red hot and then start twisting, you are going to just twist the bolt off.

Anyway, I just looked at your photos. I didn't realize the bolt went so far through. The housing that the bolt is in... what's it made from? Is that brass or metal or what?

You may be into drilling out the bolt territory here pretty soon. Do you have a drill press handy by any chance? You might be able to drill a good size hole into the bolt and drive a large screw extractor into it.

Also, when you heated it up with the torch, did the bolt glow red? What about the housing? Did you try spraying WD40 on things while it was hot (which will cause the WD40 to ignite, so be careful).

Ray

I see no reason why there should exist any female threading in the area enclosed by the red lines below. Have you succeeded in removing any of the threaded members?



Assuming that to be the case, thread, say two nuts, onto the long threaded end of the bolt remains and fit a socket over the nuts. Obviously have a little bit of clearance between the end of the socket and the flange surface. Gently tap (or a little more so) with a ball-pein hammer and the bolt may break loose.

Since the idea is to eventually separate the halves, you might consider using many non-metallic wedges and a lot of patience. Let the wedges do the work.

Edit - Another idea - smooth the threaded short end (MAYBE with an appropriate nut or thread chaser), add about 4 or so washers to the long end and a nut. Tighten the nut to apply some tension to the "bolt" and gently tap the short end with a nut partially threaded on. You may just be able to pull this "bolt" through the holes.

Have you removed this same bolt, but in another location on the boiler? If so, can you post a picture showing how the bolt looks and what's threaded, etc?

Eric makes a good point - the housing might just have a throw hole.

Ray