Hello Everyone,

I discovered this forum when I started searching for parts and found another member who lives close by that is restoring a Conti Prestina. I discovered that he and I have a similar challenge of removing the broken bolts from the broiler tank. I decided to share what I have done so far. Please Excuse the quality of the photos... I used my Android phone.

In case you are wondering how is this Block going to fit in the kitchen? It's not, I plan to set up a Barista Station in the garage:)

Here are a couple of pics of the Conti Monaco:



Various Parts and components:

Main Group head


Piston Seals


Main group.
You might be able to see the Nickle plated cylinder wall has deep scratches and chips.


Broiler Tank still mounted to the support frame


Manifold Port That is what I am calling it...
Notice the broken stud top right. all the bolts will have to be replaced...

Hi Jay,

Feel free to say I'm your neighbor and you and I are in cahoots on this project, mostly with you mentoring me on how to deal with this humongous metallurgy project! And that big box that's going to be sitting in your garage has not one but two Prestina groups!

First attempt to remove broken bolt from boiler tank.

Broken bolt one of eight that will need to be removed:(







Heat broken bolt with Oxy-Acetylene Brazing torch


Red hot bolt




Clamped Vise-Grip onto bolt
The bolt started to turn but only a quarter turn ( quarter turn CCW then quarter turn CW ) that's all it would move.



I repeated this 3 times: reheated the bolt and clamped on the Vise-Grips and still just a quarter turn.


FIRST ATTEMPT FAILED

Second Attempt.

The Vise-Grip was eating away at the broken stud. So, it was time to use a Mig welder to weld a nut onto the broken stud.

Dry fit nut on broken stud.


Welding arc omitted.


Nut welded onto stud.


Here I can now use a 9/16 wrench to turn.


Applied chemicals.


Yes! It is turning, but only 1/4 turn CCW and CW.. Go for it and.......

The nut broke off the stud and left a shorter stud to work with:(

SECOND ATTEMPT FAILED:(

STAY TUNED FOR THIRD ATTEMPT....

i have heard this tip from car mechanics working with similarly stuck studs on exhaust manifolds:

heat the stud till red hot, then quench it with the stub of an old candle..
the candle melt, the cooling and capillary action should wick some wax into the threads to help break the corrosive bond and act as a lubricant.\
then weld nut on and wrench the stud out

maybe it's worth a shot >?
i never had the opportunity to try but it seemed reasonable...

Hi coelcanth,

coelcanth wrote:heat the stud till red hot, then quench it with the stub of an old candle..
the candle melt, the cooling and capillary action should wick some wax into the threads to help break the corrosive bond and act as a lubricant.\
then weld nut on and wrench the stud out

While I have a good idea of how this is going to end on this one broken stud of 8. I am curious to see if the candle wax method has any affect. I will add it to the list of possible techniques for the other seven studs. This way readers might get an opportunity to have their suggestions put to the test....

Question: Would the the Lubricant I used have a similar affect? Or is it the composition of the wax that makes a difference?

Attempt Three

Since I have very little of the stud left to work with I am going to weld a washer to the stud and then a large nut to the washer.

Dry fit washer onto broken stud.



Weld in place.




Dry fit nut, make sure ID of nut is larger than weld.




Nut welded onto washer.


At this point the stud, washer and nut are red hot. I quickly attach a 3/4 inch wrench and carefully turned but this stud does not want to give more than a quarter turn in any direction...


Here it is cooled down. Turning it back and forth adding chemicals while increasing the torque.


Then I got a break! A clean break... Not the kind of break I wanted tho.


Back of the washer.


Predicting that this might happen I had placed an order for Screw/bolt Extractors. As soon I receive them in the mail I will post pics.

Note: I completed Steps/Attempts 1 through 3 without any breaks but posted them on the forum separately.

Very cool project, I wish you the best of luck. Just as a heads up, welding of galvanized steel is considered hazardous from a health standpoint. It looks like both the washer and the nut are galvanized. I have done it and I am still here, just don't make a habit of it! I don't want to lecture but I also want to make sure you know whats going on. This link says the major risk is intense flue symptoms with no long term health effects. I would think anything that "will cause welders to think that they have the flu in a bad way" is to be avoided!
http://www.sperkoengineering.com/html/articles/WeldingGalvanized.pdf

Nice punt on the bolt, Jay. I'll be very interested to see if you get any better result with a bolt extractor. But with results like this so far, doesn't it look like the sticking point is that the threads themselves have lost integrity? The more we deal with these things on our similar projects, the more it looks like drilling them out will be the way to go.